Waterproof Tool Bags Built for Professional Tradespeople

What a professional tool bag is actually protecting against

Most brands approach waterproof tool bags as a rain problem, and trade tool bag design as a pocket-count problem. Both miss the dominant failure. The content of a trade bag is sharp, heavy, dirty and chemically aggressive, and the container is soft. Every significant warranty claim in this category traces back to one of four mechanisms: a sharp point finding a seam or a thin panel, a load exceeding what the handle attachment or the base can distribute, a chemical softening or cracking the coating, or abrasion at the base from being dragged across a surface it was never meant to touch.

That list has an important consequence for how the product should be engineered. Rain protection is a surface property, achieved by coating and closure, and it is largely independent of the three mechanisms that actually break bags. A bag can be genuinely submersible and still fail in a fortnight because a chisel found the corner seam. Conversely, a bag with only splash resistance can last for years if the base, the seams and the coating chemistry were chosen for the contents rather than for the weather.

The second consequence is that the buyer is not the user in the way they are for consumer categories. Trade buyers — the electrician, the plumber, the HVAC engineer, the site carpenter — evaluate the bag against the specific set of tools they carry daily, and they are unforgiving about two things: whether the bag stands open so both hands are free, and whether they can see what is inside without emptying it. Those two evaluations drive repurchase far more than any printed specification, and neither is captured by a water rating.

Getting the brief right therefore starts with a contents list rather than a feature list. Our companion review of waterproof bags for construction and utility work sets out the site conditions that define the category; this piece stays closer to the object itself. The question to answer first is simply: what is the sharpest, heaviest and dirtiest thing this bag will hold, and how often will it be set down in something wet?

Puncture and cut-through: the failure that ends a bag

Puncture is not abrasion. Abrasion removes material gradually over thousands of cycles and gives warning; puncture is a single event that converts a bag into a container with a hole in it, and it happens most often at rest rather than in motion. A chisel dropped point-first into a loaded bag, a drill bit carried loose, the corner of a spirit level pressed against a panel while the bag is lifted — each applies a small contact area with considerable force, and coated woven fabric resists that badly if the force lands on a seam.

Two mechanics matter. First, puncture resistance scales with coating thickness and film toughness more than with fabric denier, because the sharp point has to break through a polymer layer before it can separate yarns. A TPU film laminate of 0.4 to 0.6 millimetres on a 1000D base resists a dropped chisel measurably better than a thinner PU coating on the same yarn. Second, the weakest place is always a seam, because needle perforations interrupt the coating and the stitch thread itself is far weaker than the film. A welded construction has no perforations at all, which is the strongest argument for welding the base and lower panels of a trade bag even when the upper body is sewn for cost.

Design responses that actually work are mostly about separating the sharp object from the fabric rather than about making the fabric infinitely strong. Rigid or semi-rigid sleeves for blades and bits, a separate bit roll, and internal walls that hold long tools vertically rather than letting them lie against the side all reduce puncture events by removing the contact rather than resisting it. This is cheaper than upgrading the whole shell, and it is the difference between a bag that survives five years and one that is replaced every season.

Testing for this is straightforward and rarely done. A drop-puncture test — a defined pointed mass dropped from a set height onto a clamped panel — gives a comparable number between materials and constructions, and it is the test that most reliably predicts field puncture. Standard tensile and tear figures, such as those covered in our piece on tear, tensile and burst testing, describe how a fabric behaves once a cut exists; they say little about whether the cut starts.

Load capacity and the open-mouth problem

Fifteen to twenty-five kilograms is the realistic working range for a trade tote or tool bag, and the number matters far less than what that load does to the shape of the opening. A soft bag under load pulls its mouth inward, so the user loses the wide access that made a tote the right format in the first place. The bag becomes a bucket that has to be held open with one hand, which is precisely the failure that ends repurchase.

There are three ways to hold a mouth open, and they sit at very different price and weight points. A rigid or semi-rigid collar moulded into the top edge, usually a polypropylene or HDPE extrusion sewn or welded into a sleeve, gives the most reliable result and adds around 150 to 300 grams. A heavy interlining in the wall panels gives partial rigidity, degrades with creasing, and never fully recovers. A wire or plastic frame at the rim gives excellent access but is the most expensive and the most likely to be damaged if a van drives over the bag.

For most trade lines the collar is the right choice, with one caveat: the collar has to be continuous or nearly so. A collar that stops at each handle attachment leaves two flexible zones at exactly the points where the load is highest, and the mouth collapses there first. If a design needs the collar interrupted for a handle, the handle should be attached to the collar rather than to the fabric beside it, so the load path runs through the rigid member.

The load path question then extends to the base. A loaded tool bag set down hard on concrete delivers the whole mass through a small area, and if the base is a single layer of coated fabric the concentrated load drives tool corners into the seam. A moulded base tray, or a double layer of high-denier fabric over a stiffener, spreads that load. Our discussion of load stress testing on straps and handles covers the pull-testing side; the base needs the same discipline applied downward rather than upward.

One practical specification saves a surprising amount of grief. State the rated carried load on the product or the hangtag, and test to a multiple of it. A bag rated to 20 kilograms and tested to 60 kilograms static with no failure and no permanent deformation is a defensible claim; a bag with no stated rating invites the user to put forty kilograms of fixings in it and then blame the bag. Rating is a liability management tool as much as a marketing one.

Oil, solvent and chemical compatibility

This is the area where material selection is least forgiving and most often guessed. Trade bags meet hydraulic oil, diesel, cutting fluid, mineral spirits, solvent-based adhesives, expanding foam, brake cleaner and wet concrete, and each attacks coatings differently. A coating that performs perfectly against water can soften, swell, haze or craze within days of a spill, and the failure is usually reported as a quality problem rather than as a chemistry problem.

The general conclusion for trade lines is that TPU outperforms PVC and most PU coatings against oils and solvents, and that a welded polyethylene or polypropylene liner outperforms every coating for genuinely aggressive substances. That is why the more capable trade bags use a hybrid: a tough woven shell with a TPU or PVC coating for abrasion and structure, and a separate welded polyolefin liner in the compartment where chemicals and wet material actually go.

There is a specification trap here that is worth naming. A liner that is chemically resistant but not mechanically tough will puncture, and a liner that is tough but not resistant will degrade. Buying a thick liner does not solve both problems; the liner gauge and the liner polymer are separate decisions. Immersion and resistance methods for coated fabrics are catalogued by bodies such as ASTM International, and citing one by number is what turns a chemical claim into something enforceable. Our deeper treatment of chemical resistance in waterproof materials sets out the compatibility logic in more detail, and the site-specific version for energy work is covered in our notes on bags for oil and gas applications.

Hardware deserves its own line in this discussion because it is frequently the first casualty of a chemical spill. Zinc-plated steel corrodes quickly in salt or cement slurry; brass tarnishes and stains fabric; standard zamak pulls pit. For trade use, specify either stainless or a coated zamak with a stated salt spray result, and accept that this is one of the few places where the upgrade is genuinely visible to the user within weeks.

Base construction: feet, skids and the wet floor

The base of a trade bag does three jobs that are usually specified as one. It carries the load, it resists abrasion from being set down and dragged, and it keeps the contents out of standing water. A flat fabric base does the first adequately, the second badly, and the third not at all — and standing water is a routine site condition rather than an edge case.

Raised feet of 5 to 8 millimetres are the minimum useful intervention, and they should be moulded rather than riveted-on blocks, because a rivet through the base is a puncture-adjacent hole in the most loaded panel of the bag. Moulded skids running along the length perform better than discrete feet on rough ground and distribute the load along the base rather than at four points. A fully moulded tray is the most capable and the most expensive, and it has a real advantage beyond protection: it can be hosed out.

Drainage is the detail that separates a considered design from an assumed one. If the base is sealed and waterproof, water that gets in stays in. Either provide drain grommets at the lowest corners — which slightly compromises the waterproof claim but massively improves real-world behaviour — or provide a welded inner tray that can be emptied. Trade users overwhelmingly prefer a bag that drains over a bag that holds a puddle, and they will tell you so in reviews.

Abrasion at the base is worth a specific denier decision. Upgrading the whole shell to 1680D to protect the base adds weight and cost everywhere for a benefit needed in one place; specifying a 1680D or 1000D base panel over a 600D body achieves most of the protection at a fraction of the penalty. The standards commonly cited for quantifying this are discussed in our review of abrasion resistance standards, and the practical guidance is to test the base panel separately from the body rather than quoting one figure for the whole bag.

Compartment strategy and visibility

Compartment design in a trade bag is a visibility problem before it is an organisation problem. A tradesperson working at height, in a crawl space or in poor light needs to identify and retrieve a specific tool by touch or by a single glance. A bag with fourteen pockets of similar size is worse than a bag with six well-differentiated ones, because the user cannot build a mental map of where anything lives.

• Differentiate pocket sizes rather than multiplying them: two deep pockets for large hand tools, a bank of narrow sleeves for screwdrivers and chisels, one shallow tray for fixings.
• Use a light-coloured or high-visibility interior lining. Dark linings are the single most common complaint in this category, because a black interior is unsearchable in a dim plant room.
• Put sleeves at the walls, not in the centre, so long tools stay vertical and their points do not migrate toward the base seam or the closure.
• Give every sharp tool a dedicated sleeve with a rigid or semi-rigid insert; loose storage in the main void is the primary puncture mechanism.
• Provide at least one compartment that can be hosed or wiped clean, separate from the compartment holding electrical test equipment and documentation.
• Keep the fixings pocket shallow and wide — a deep narrow pocket buries screws under each other and is universally disliked.

Electrical and test equipment deserves its own consideration because it is the expensive content. A padded, sealed compartment for a multimeter or a thermal camera, positioned away from the wall that takes site impact, protects an item worth several times the bag. This is a strong upsell in trade channels and a cheap one to engineer, and it is the feature most often cited in five-star reviews when present.

There is a manufacturing consequence to pocket count that belongs in the costing conversation. Each pocket is a cut part, a sewing operation and a quality surface. Going from six pockets to fourteen can add more conversion cost than upgrading the shell material, and it adds defect opportunities in direct proportion. The pocket count should be defended on user research rather than on competitive comparison, because the cost is real and returns do not improve with it.

Drop, drag and the van-to-site journey

Most of the damage a trade bag accumulates happens outside working hours, in the back of a van, in transit between jobs. Bags are stacked, sat on, slid across a metal floor, and occasionally driven over. None of that appears in a product description, and all of it shows up in warranty statistics.

The useful test is a loaded drop from roughly one metre onto concrete, repeated at several orientations: flat on the base, on a corner, and on the handle. Each orientation interrogates a different component. Flat-on-base tests the tray or the base seam; corner tests the corner reinforcement and the weld; handle-down tests the attachment. A bag that survives ten such drops with no structural failure is well specified; a bag that fails on the second corner drop has a corner construction problem that will surface in the field within a month.

Drag abrasion is the second transit mechanism and it is almost never tested. A bag pulled across concrete by its handle abrades the base corners and the lower wall in a way no Martindale figure predicts, because the load is concentrated and the abrasive is not a standard cloth. If the product is likely to be dragged, a moulded skid is the only reliable answer, and a reinforced lower wall band is the cheap partial one.

Compression in transit matters for bags shipped assembled rather than flat. A structured tool bag stacked under other cargo for a multi-week voyage takes a sustained load that can permanently deform a collar or a stiffener. Our guidance on packaging and shipping damage prevention covers the carton specification side; the product-side answer is to specify that collars and trays are sleeved or removable so that transit compression does not set a permanent deformation into a part meant to hold a shape.

Handles, grab points and shoulder carry

A loaded trade bag is lifted far more often than it is carried, and the lift happens from whatever is nearest — usually the handles, sometimes a corner, occasionally the shoulder strap. Handle design for this category therefore differs from consumer bags in one important way: the handle has to be grippable with a gloved hand while taking a load of twenty kilograms.

That requirement sets a width and a section. A flat webbing handle of 38 to 50 millimetres with a padded or moulded grip spreads the load across the palm well enough to be carried one-handed for short distances; a 25 millimetre webbing handle concentrates it into a line that becomes painful at fifteen kilograms. Many trade bags solve this with a moulded plastic or rubber-wrapped grip over a webbing core, which also survives oil contamination far better than fabric padding does.

Grab points at the ends of the bag are the second necessity, because a loaded bag is often lifted from a van shelf or out of a tight space where the top handles are not accessible. Two reinforced end grabs, sewn into the wall panel with a load path into the base, cost very little and are used constantly. Their absence is one of the more common complaints in trade reviews and one of the cheapest things to fix at sampling.

Shoulder carry is a genuine requirement for longer walks across site, and it only works if the strap attachment points are engineered for it. Attaching a shoulder strap to the same patches as the top handles puts an angled load on a reinforcement designed for a vertical one, which is why straps tear off trade bags that were never designed to be slung. If a shoulder strap is offered, the attachment needs its own reinforcement and its own test, and the trade-off in weight and cost should be accepted rather than avoided.

Hardware selection interacts with all of this, and it is worth being specific: the buckle or adjuster in the load path should be rated well above the carried load, because a buckle that slips under twenty kilograms converts a comfortable carry into a dropped bag full of tools. Our review of hardware selection for buckles and straps covers the rating logic; the rule of thumb is to specify hardware at several times the rated carried load, not at parity with it.

Sizing and the carried weight budget

The temptation in trade categories is to size up, because bigger reads as better value on a shelf. The consequence is a bag that is never carried at less than twenty kilograms and that does not fit in the space a van actually has. Real trade behaviour splits fairly cleanly into three sizes, and covering two of them well is a better range than covering all three badly.

A compact service bag of roughly 8 to 14 litres carries the daily hand tools for a single trade — drivers, pliers, a tester, a small meter — and weighs six to nine kilograms loaded. A mid bag of 20 to 30 litres carries a broader kit including a drill and chargers, at twelve to eighteen kilograms. A large holdall of 40 litres and above is a transport container for a full kit rather than something carried to a workface, and it should be designed with wheels or a very different handle arrangement.

The empty weight budget follows from this. A trade bag should not exceed roughly 1.2 kilograms empty at the mid size, because the user is already carrying the tools and every gram of container is a gram they feel. Occupational guidance on manual handling, such as that published by the US Occupational Safety and Health Administration, treats carried weight and lift frequency as a combined exposure, which is the right way to read a tool bag specification. This is where the structural decisions above have to be traded honestly: a moulded tray, a collar and reinforced side panels all add weight, and the only place to take it back is the shell denier on panels that are not load-bearing.

Dimensional discipline matters for a logistics reason too. A structured bag that does not nest or collapse occupies its full volume in a carton, and freight per unit rises sharply with size in this category. Our notes on dimensional customisation show how packed cube is calculated, and the practical guidance is to check the carton count before signing off a size increase that seemed free at the design stage.

How waterproof a tool bag needs to be

Genuinely submersible construction is usually the wrong answer for a trade bag, and the reason is practical rather than technical. Submersible closures — roll-tops with buckles, long watertight zips — are slow to open, and a tradesperson opens the bag dozens of times a day. A closure that takes four seconds instead of one will be left open, at which point its rating is irrelevant. The functional requirement is resistance to rain, splashes and standing water, plus the ability to be cleaned, and that is a much cheaper specification.

In rating terms, splash and rain resistance with a sealed, cleanable base covers the great majority of trade use. Submersion matters only where the work is genuinely wet — marine, water utility, external drainage — and in those cases the right answer is usually a sealed compartment for the items that must stay dry rather than a submersible bag, because the user still needs fast access to the tools.

Cleanability deserves more attention than it gets, because it is what the waterproof construction actually buys in daily use. A smooth welded base that can be hosed out, a liner that can be wiped, and hardware that does not corrode when it gets wet are the three properties that make a trade bag feel like a professional tool rather than a bag. All three are cheap to specify and none of them is captured by a water rating.

The rating language itself should be used carefully. Fabric-level and product-level ratings are different claims, and quoting a fabric hydrostatic head as though it described the assembled bag is the most common specification exaggeration in the category. Our guide to the IPX rating system explains the distinction; for trade lines the defensible approach is to state a fabric figure for the material and a separate product-level result for the assembled bag, and to publish only the latter in consumer-facing copy.

Material sets and denier choices for trade use

Denier is quoted constantly and understood loosely. It describes yarn thickness, and therefore mass per area, and it correlates with abrasion and tear resistance — but only within the same fibre and construction. A 600D polyester and a 600D nylon behave differently, and a coated 420D can outperform an uncoated 1000D in abrasion because the coating is what the ground touches. Denier should be specified alongside the coating and the weave, never alone.

The pattern across that table is consistent: there is no single best material, and the competent specification is a zoned one. Heavy high-denier fabric and a tough film at the base and lower walls, a lighter coated fabric in the upper body and lid, and a chemically resistant welded liner wherever liquids are expected. A bag built from one material throughout is either overbuilt and heavy or underbuilt at the base, and it costs more than a zoned construction in either direction.

Two material notes specific to site conditions. UV exposure matters because trade bags are frequently left in direct sun on a site or in a van window for months, and both polyester and nylon lose strength under UV with polyester generally performing better than nylon in this respect. Our review of UV resistance in outdoor bag materials covers the testing; the practical guidance for trade lines is to specify a UV-stabilised coating for bags that will live outdoors. And hydrolysis matters for storage: PU-coated fabric stored in humid conditions can degrade before sale, which is a particular risk for slow-turning trade inventory.

Our separate comparisons of Cordura-type fabrics in bag construction and what denier ratings actually predict go deeper on both points, and both are worth reading before a first trade specification is frozen because material changes after tooling are expensive.

Failure modes: what warranty claims actually say

Warranty and return narratives in trade categories are unusually blunt, and reading them produces a short, repeatable list. Each entry maps to a specification decision, and the value of the list is that it tells a development team where to spend its testing budget.

What is striking is how few of these are water ingress in the ordinary sense. The category is marketed on waterproofing and returned on mechanics and chemistry, which means a development programme that allocates its effort in proportion to its marketing claims will test the wrong things repeatedly and never discover that the base seam is the problem.

The category-wide view of these defects, and how they are prevented at the process level rather than the design level, is set out in our guide to common waterproof bag defects and their prevention. Reading it alongside this piece gives the full picture: this article covers which specification prevents the defect, that one covers which process control keeps the specification honest across a production run.

Testing, specification and building a trade line

A trade specification should be written as a set of numbers with test methods attached, not as a list of adjectives. "Heavy duty" and "professional grade" are unenforceable; a stated carried load, a drop height, an abrasion cycle count and a chemical exposure list are enforceable, and they are also the only basis on which two quotations can be compared honestly.

• State the rated carried load and test to a multiple of it, recording the failure mode rather than only the load at failure.
• Run a drop-puncture test on candidate base constructions with the actual sharp tools from the contents list, not a standard probe.
• Test chemical exposure on the coating and on the liner separately, with the specific substances your trades encounter, and inspect after 24 hours rather than immediately.
• Test the closure for speed of opening as well as water resistance; a closure that is left open has no rating at all.
• Test drag abrasion on the base corners with the bag loaded, since standard abrasion figures do not predict it.
• Salt spray test the hardware, because hardware corrosion generates more complaints than fabric failure in wet trades.

On the commercial side, the governing number is the minimum order quantity of 500 pieces per style. A trade range is naturally segmented — compact, mid and large, often across two or three trades — and at 500 per style a five-style launch is 2,500 units, which is a serious commitment. The usual way to make that work is to share tooling and structure across the range: one base tray, one collar extrusion and one hardware suite used across three sizes, with differentiation carried by pocket layout, colourway and logo.

Logo treatment on trade bags has its own logic. This is a category where a visible, durable mark matters for brand recognition on site and in vans, and where the mark is exposed to abrasion and solvents. Screen print with a compatible ink system on a coated shell is the default; embroidery perforates the shell and is therefore a poor choice where water resistance is claimed; a rubber or PVC patch is durable and reads well but adds a part and a bonding operation. Our detailed review of logo printing and embroidery options sets out the constraints for each method on coated substrates.

Pricing in trade channels is unusually rational: buyers compare against the cost of replacing tools, not against other bags. A bag that demonstrably protects a two-thousand-dollar meter is sellable at a price that would be absurd in a consumer channel, and the way to earn it is to engineer the protected compartment and publish the test result. That is a more reliable margin strategy than competing on pocket count.

Timing for a trade launch follows the standard shape — sampling in 6–10 working days per round, bulk production in 35–50 days, quoted FOB Xiamen — and the planning discipline is to work backwards from the trade season rather than forwards from sample approval. Our guide to lead times on custom orders covers the sequence in full. If you want these decisions turned into a costed trade specification, send the contents list, the target carried load and the substances the bag will meet. Minimum order quantity is 500 pieces per style, samples take 6–10 working days, bulk production runs 35–50 days, and quotations are issued FOB Xiamen.

Frequently Asked Questions

Q1. Is a fully submersible tool bag better for trade use?

Usually not. Submersible closures are slow to open, and a bag opened dozens of times a day will be left unsealed. Rain and splash resistance with a cleanable sealed base covers most trade work.

Q2. What actually punctures a tool bag?

Sharp tools resting or dropped against a seam. Chisels, drill bits and blade corners concentrate force into a small area, and needle perforations in a stitched seam are the weakest point in the construction.

Q3. Should the base of a tool bag be welded or stitched?

Welded. A welded base has no needle perforations and no thread to fail, and puncture resistance comes from the film rather than from the yarn. Welding the base while sewing the upper body is a common, cost-effective compromise.

Q4. How much weight should a trade tool bag carry?

Fifteen to twenty-five kilograms is the realistic working range. State a rated load and test to a multiple of it; an unrated bag invites overloading and the resulting warranty claim.

Q5. Why does the mouth of my tool bag collapse when loaded?

Because there is no rigid member at the rim. A continuous moulded collar holds the opening; a collar interrupted at the handle attachments fails at exactly the points where the load is highest.

Q6. Which coating resists oil and solvents best?

TPU generally outperforms PVC and PU coatings against oils and spirits. For aggressive substances such as solvent adhesives or expanding foam, a welded polyethylene or polypropylene liner is more reliable than any coating.

Q7. Do I need drainage in a waterproof tool bag?

In most trade applications, yes. A sealed base that collects water is worse in daily use than a base that drains, and trade users consistently prefer drainage over a nominal waterproof claim.

Q8. What height of feet keeps contents out of standing water?

Five to eight millimetres of moulded feet or skids is the practical minimum. Moulded skids distributed along the base outperform four discrete feet on rough ground.

Q9. Why is a light-coloured interior important on a trade bag?

Because tools are searched for by eye in poor light. A dark lining is unsearchable in a plant room or a crawl space and is among the most common complaints in this category.

Q10. What denier should a trade bag use?

Zone it rather than picking one figure: 1680D or 1000D with a tough coating at the base and lower walls, 600D in the upper body and lid. Denier alone does not predict performance without the coating specification.

Q11. How should I test for puncture before production?

Drop a defined pointed mass onto a clamped panel, using the actual tools from the contents list rather than a standard probe. Standard tear and tensile figures describe behaviour after a cut, not whether one starts.

Q12. Does hardware corrode before the fabric fails?

Frequently, yes, in wet and salted environments. Zinc-plated steel and untreated zamak pit quickly around cement slurry and de-icing salt; stainless or coated hardware with a stated salt spray result is worth specifying.

Q13. Should a trade bag have a shoulder strap?

Only if the attachment is engineered for it. A strap anchored to the handle reinforcement puts an angled load on a patch designed for a vertical one, which is why straps tear off bags never meant to be slung.

Q14. How heavy should the empty bag be?

Around 1.2 kilograms or less at the mid size. The user is already carrying the tools, and container weight is felt directly; take weight out of non-load-bearing shell panels, not out of structure.

Q15. What is the best way to protect expensive test equipment?

A padded, sealed compartment positioned away from the wall that takes site impact. Protecting a meter worth several times the bag is a strong upsell and cheap to engineer.

Q16. How many styles should a trade launch include?

Two or three sizes sharing one base tray, one collar and one hardware suite, differentiated by pocket layout, colour and logo. At 500 pieces per style, each additional style is a real inventory commitment.

Q17. Which logo method survives trade conditions?

Screen print with a compatible ink system, or a rubberised patch. Direct embroidery perforates a waterproof shell and should be avoided where water resistance is claimed unless it is applied before assembly and sealed.

People Also Ask

Are waterproof tool bags worth it for tradespeople?

Yes, mainly for cleanability and chemical resistance rather than rain. A sealed base that can be hosed out is the property that changes daily work.

What material is best for a tool bag base?

A welded high-denier panel with a 0.5 mm film and moulded skids. Puncture resistance comes from the film, not the yarn count.

How much weight can a tool bag hold?

Fifteen to twenty-five kilograms in normal trade use. Buy a bag with a stated rated load and a test result to support it.

Why do tool bags get holes in the bottom?

Sharp tools press or drop into the base seam, and stitched seams are the weakest point. Welded bases and rigid tool sleeves prevent it.

Does oil damage waterproof bag coatings?

Yes. Oil swells PVC and attacks many PU coatings. TPU performs better, and a welded polyolefin liner is more reliable still for solvents.

Should a tool bag be fully waterproof or just water resistant?

Water resistant with a cleanable sealed base. Fast access matters more than submersion, and a slow closure will be left open anyway.