Pool Losing Water
Every pool loses water to evaporation — commonly a quarter to half an inch a day in hot, dry weather. The bucket test tells you in 24 hours whether yours is losing more than that, and it costs nothing.
Is it urgent?
A slow leak is not an emergency, but it is not something to leave for a season either. Water escaping into the surrounding soil erodes the support under your deck and, in the worst cases, under the shell itself. What starts as a rising water bill can end as a settling deck.
Rapid loss — inches per day rather than fractions of an inch — is a different matter. That suggests a significant line break and can undermine surrounding structures quickly.
The bucket test
This is the standard way to separate a leak from evaporation, it requires nothing but a bucket, and every professional will ask whether you have done it.
- Fill a bucket with pool water. Use pool water, not tap water, so the temperature matches.
- Set it on a step, weighted. Position it so the water level inside the bucket matches the pool level outside it.
- Mark both levels. Tape or a grease pencil on the inside and outside of the bucket.
- Wait 24 hours with the pump running normally. Evaporation affects both the same way, so the difference between them isolates the leak.
- Compare. Levels dropped equally — evaporation, no leak. Pool dropped noticeably more — you have a leak.
- Then repeat with the pump off. This is the step people skip, and it is the most useful. If the loss is worse with the pump running, the leak is on the pressure side. If it is the same either way, it is likely the shell or a fitting.
Where leaks usually are
| Location | Clue | Typical repair cost |
|---|---|---|
| Skimmer / skimmer throat | Loss stops at the skimmer mouth level | $300–$900 |
| Light niche and conduit | A very common and often overlooked path | $300–$1,000 |
| Return fittings | Worse with the pump running | $200–$700 |
| Pressure-side plumbing | Worse with the pump running; wet ground nearby | $800–$3,500 |
| Suction-side plumbing | Air bubbles in the pump basket; worse pump off | $800–$3,500 |
| Main drain | Loss continues below all other fittings | $1,000–$4,000 |
| Shell crack | Visible crack; loss steady regardless of pump | $500–$3,500 |
| Vinyl liner tear | Liner pools only; often findable visually | $150–$500 patch |
Other things you can safely check
- Note where the water stops falling. If it stabilises level with the skimmer mouth, that is your leak. If it stops at the light, likewise. This alone often locates it.
- Look for unusually lush or soggy ground. A green patch in an otherwise dry lawn, or persistently wet soil near the equipment pad, points at a buried line.
- Watch the pump basket for air. Persistent bubbles indicate a suction-side leak drawing air in — the same fault that lets water out when the pump is off.
- Check for settling around the pool. Deck sections dropping or coping separating can be a consequence of water washing out the sub-base.
- Rule out the obvious. Backwashing, heavy splash-out, a leaking filter or a stuck autofill can all masquerade as a leak.
What not to do
- Do not pour leak-sealing products in as a first step. They can work on very small shell leaks, but they also coat filters and plumbing. Locate the leak first; use sealants as a considered choice, not a shot in the dark.
- Do not let the level drop below the skimmer. Running a pump that is drawing air damages the pump seal and can burn out the motor.
- Do not drain the pool to look for a leak. Draining risks shell damage from groundwater and rarely reveals anything a professional could not find with the pool full.
- Do not dig speculatively. Leak detection uses pressure testing and acoustic equipment precisely so nobody has to excavate a whole yard on a guess.
What detection and repair cost
| Stage | Cost | Notes |
|---|---|---|
| Bucket test | $0 | Do this before calling anyone |
| Professional leak detection | $250–$600 | Pressure testing and acoustic location |
| Fitting or skimmer repair | $200–$900 | The most common outcome |
| Plumbing line repair | $800–$3,500 | Depends heavily on access and depth |
| Shell crack repair | $500–$3,500 | Often followed by resurfacing |
| Liner patch or replacement | $150–$500 / $3,800–$6,500 | Vinyl pools |
How to read a PoolSavr estimate
- Step 1
Instant estimate
Based on your project selections and general pricing assumptions. Useful for deciding whether a project is realistic.
- Step 2
Measured estimate
Uses your pool, spa, or deck dimensions to price the work against the areas actually being resurfaced, tiled, or replaced.
- Step 3
Contractor proposal
Prepared by a licensed professional after inspecting the site. This is the only number that becomes a contract.
PoolSavr is an estimating and matching platform. We do not perform pool work ourselves — licensed local professionals do. Contractors pay PoolSavr for qualified project leads, which is how the estimating tools stay free for homeowners. A PoolSavr estimate is a planning range, never a guaranteed quote — read thefull estimate disclaimer.
Frequently asked questions
- How much water loss is normal for a pool?
- A quarter to half an inch a day is typical, and hot, dry, windy conditions push it toward the upper end. Anything beyond about half an inch a day, or any loss that does not track the weather, is worth testing.
- How do I know if my pool is leaking?
- The bucket test. Fill a bucket with pool water, set it on a step so the levels match, mark both, and wait 24 hours with the pump running. Evaporation affects both equally — if the pool drops noticeably more than the bucket, you have a leak. Then repeat with the pump off to narrow down where.
- Where do pools usually leak?
- The skimmer and its throat, the light niche and conduit, return fittings, and the plumbing lines. Structural cracks in the shell are less common than people assume. On vinyl pools, liner tears are the usual answer.
- How much does pool leak detection cost?
- Typically $250–$600 for professional detection using pressure testing and acoustic equipment. Many companies credit that against the repair if you use them for it. Repairs range from $200 for a fitting to $3,500 for a buried line.
- Can I just add water and ignore it?
- For a very slow leak, some people do — but it is worth understanding what you are accepting. Beyond the water cost and constantly diluted chemistry, water escaping into the soil erodes the support under your deck and can eventually cause settlement that costs far more than the leak repair.
Ready to see what your project costs?
Start with the work you are considering. You will get a preliminary range before anyone asks for your phone number, and you decide whether to request a contractor review at the end.