A quarter-sized dab of water-finding paste on a gauging stick tells you in seconds whether water has settled at the bottom of a fuel storage tank — no lab, no meter, no downtime. This guide covers how the paste works, how to run the test correctly, and which Kolor Kut paste fits gasoline and diesel versus a broader range of fuels and chemicals.
What Is Water-Finding Paste?
Water-finding paste is a petroleum-industry field test compound that changes colour on contact with water, applied to the end of a gauging stick or tape and lowered into a storage tank to measure water depth by sight.
The paste is smeared in a thin, even coat on a wooden gauging stick or the weighted end of a gauging tape, then lowered to the bottom of the tank and held there for a few seconds before being withdrawn. Any water pooled at the bottom reacts instantly and visibly, while the section of the stick that only touched fuel keeps the paste's original colour. Because petroleum products float on water, water always collects at the lowest point of the tank — the same basic method applies whether the tank is an underground storage tank (UST), an aboveground storage tank (AST), a day tank, or a bulk terminal vessel.
Why Fuel Tanks Accumulate Water
Three sources account for most water found in fuel storage tanks: condensation from temperature swings inside a partially empty tank, groundwater intrusion through a compromised UST fitting, seam, or vent, and contamination introduced during a fuel delivery. Even a shallow water layer promotes microbial growth at the fuel/water interface (commonly called "diesel bug" in diesel systems), accelerates corrosion of the tank bottom, and can be drawn into fuel dispensers or engines during drawdown if it isn't caught.
How Does Water-Finding Paste Work?
The paste contains a colour-change compound that reacts specifically with water, not with hydrocarbons — so a section of stick that only contacted fuel keeps the paste's original gold-brown colour, while any section that touched water turns bright red within seconds of contact.
That selectivity is what makes the test useful in the field: the colour boundary on the stick marks the exact fuel/water interface, so measuring from the bottom of the stick to the colour-change line gives a real water-depth number, not just a yes/no indication.
How Do You Gauge a Tank With Water-Finding Paste?
The procedure is the same one used across the petroleum industry for manual water-cut checks, and it takes under a minute once you have the right paste for the product in the tank.
- Select the right paste for the product in the tank. For gasoline, diesel, or other straight hydrocarbon storage, use Kolor Kut Gasoline Gauging Paste. For a wider range that includes acids, ammonia, or salt/chloride solutions alongside petroleum products, use Kolor Kut Water Finding Paste.
- Apply a thin, even coat of paste to the last 5–8 cm (2–3 in) of a wooden gauging stick or the weighted end of a gauging tape.
- Lower the stick or tape smoothly to the bottom of the tank without splashing it against the sides, and hold it against the bottom for several seconds.
- Withdraw the stick in one smooth motion and read the colour change immediately — the paste keeps reacting the longer it sits exposed to air, so read and record the line before wiping it down.
- Measure the water cut from the bottom of the stick to the colour-change line to get an actual water depth, not just a pass/fail result.
- Log the reading in your tank inventory or environmental compliance record, and compare it against your facility's action threshold before deciding whether to pump the water out or investigate further.
Water-Finding Paste vs. Gasoline Gauging Paste: Which One Do You Need?
Both Kolor Kut Water Finding Paste and Kolor Kut Gasoline Gauging Paste use the same red-on-water colour-change reaction — the difference is compatibility range and pack format.
| Water Finding Paste | Gasoline Gauging Paste | |
|---|---|---|
| Reacts with | Water only — no colour change from the product itself | Water only — no colour change from the product itself |
| Compatible products | Petroleum products, plus sulfuric, nitric, and hydrochloric acid, ammonia, soap solutions, and salt/chloride solutions | Gasoline, diesel, naphtha, kerosene, oil, crude oil, jet fuels, and other hydrocarbons |
| Pack size | 3 oz tube | 2.25 oz jar |
| Best fit | Multi-product terminals or sites also gauging chemical/acid storage | Straight fuel storage — retail fuel sites, fleet fuelling, generator/day tanks |
If your site only stores gasoline, diesel, or similar hydrocarbons, Gasoline Gauging Paste is the simpler, purpose-built choice. If your facility also gauges tanks holding acids, ammonia, or salt solutions, Water Finding Paste's wider compatibility list covers more of your operation with one product on the shelf.
Why Does Water in a Fuel Tank Matter?
Water in a fuel storage tank is both a compliance signal and an equipment risk in Canada — storage tank systems regulated federally are required to monitor tank and fitting integrity, and water intrusion is one of the clearest field indicators that a tank, fitting, or vent needs attention.
Under the Storage Tank Systems for Petroleum Products and Allied Petroleum Products Regulations (enacted under the Canadian Environmental Protection Act), federally regulated storage tank systems must be monitored for leaks and structural integrity — a routine water-cut check is a low-cost field practice that surfaces the same underlying problem a leak-detection system is designed to catch. Provincial and municipal UST programs generally layer additional inspection requirements on top of the federal baseline. Because both Kolor Kut pastes are handled directly and carry manufacturer safety data sheets, always review the product's SDS and follow standard WHMIS handling practices (gloves, eye protection, ventilation) before use.
For broader environmental field equipment beyond tank gauging — sampling pumps, bailers, and groundwater monitoring gear — see ERE's water and liquid sampling collection.
Need water-finding or gauging paste for your site?
ERE Inc. has supplied environmental and petroleum-handling field equipment across Canada for 30+ years. Talk to a real specialist about which paste fits your tank inventory.
→ Request a Quote | 1-888-287-EREC | Browse Sampling Equipment | sales@ereinc.com
Frequently Asked Questions
Does water-finding paste work on diesel and other fuels, or just gasoline?
Kolor Kut Gasoline Gauging Paste is formulated for gasoline, diesel, naphtha, kerosene, oil, crude oil, jet fuels, and other hydrocarbons. Kolor Kut Water Finding Paste covers an even wider range, including petroleum products plus acids, ammonia, soap solutions, and salt/chloride solutions.
How much water in a fuel tank is a problem?
There's no single Canada-wide number — your facility's monitoring program or the storage tank's operating permit sets the action threshold. What water-finding paste gives you is a fast, visible measurement of exactly how much water is present, so you can compare it against your own procedure and decide whether to pump it out or investigate further.
Can water-finding paste replace electronic tank monitoring?
No — paste gauging is a manual spot-check, not continuous monitoring. It's a fast, low-cost complement for daily or weekly checks, or for verifying an electronic system's reading, not a substitute for the leak-detection and inventory-control systems most storage tank regulations require.
Related articles
- Fluorescent Tracer Dyes: Leak Detection & Water Tracing Guide for Canada
- Sewer Dye Testing: How to Detect Illicit Connections and I&I Sources
- Environmental Sampling Equipment: The Complete Guide for Canada
Lire en français : Pâte de détection d'eau : comment détecter l'eau dans un réservoir de carburant