How to Check a Pool Autofill Pot for Cracks and Leaks

We can agree that a pool autofill is easy to forget about until something seems wrong. The small covered pot beside the pool may quietly add water for years, so a crack in the housing, a leaking connection, or a problem around the fill valve can be surprisingly difficult to notice. Knowing how to check a pool autofill pot for cracks and leaks can help you separate a problem in the autofill assembly from ordinary evaporation or water loss somewhere else in the pool.

An autofill pot, sometimes called an automatic water-leveler canister, usually contains a float-operated valve connected to a pressurized fresh-water supply. The pot also communicates with the pool through a separate opening or equalizer line so the water inside the pot rises and falls with the pool. That means there can be several completely different leak paths in a very small area.

Start by understanding what can actually leak

Do not assume that water around an autofill automatically means the plastic pot itself is cracked. The problem could be the fresh-water fitting, the valve connection, the line between the pot and pool, or the body of the pot.

• Autofill pot or canister: A hairline split in the wall, bottom, or molded fitting area may let pool water escape into the surrounding soil.
• Fresh-water supply connection: A threaded fitting or pipe joint can leak whenever the autofill supply is pressurized.
• Float valve: A worn or scaled valve may continue admitting water even when the pool has reached the proper level.
• Pool-side equalizer connection: A failed fitting or underground line between the pot and pool can create water loss even when the canister looks intact.

1. Turn off the fresh-water supply first

Locate the valve that supplies household water to the autofill and shut it off. Confirm that the float valve no longer releases fresh water when you gently lower the float. If water continues flowing, the shutoff may not be fully closed or you may have identified the wrong valve.

This step matters because a live supply line can hide what is happening. A leaking pot could lose water while the float valve continuously replaces it, leaving the level looking perfectly normal.

2. Remove debris and inspect the entire pot

Take off the autofill lid and remove leaves, dirt, insects, scale, and other debris that prevent you from seeing the housing. Use a flashlight even during daylight. Hairline cracks can disappear against wet or dirty plastic.

Pay extra attention to areas where stress tends to concentrate: around threaded valve connections, molded pipe openings, corners or transitions in the housing, and the bottom of the canister. Look for thin lines, discoloration, mineral deposits, or a previously repaired area.

White mineral deposits can be especially helpful clues. They do not prove an active crack, but repeated water movement can leave residue along a fitting or damaged section as the moisture evaporates.

3. Determine whether the suspicious area is above or below the waterline

The location of a crack changes its symptoms. A crack below the normal water level can allow pool water to migrate out of the canister even when the freshwater supply is turned off. A crack higher on the housing may stay dry most of the time and leak only when the float valve sprays, splashes, or raises the water unusually high.

This distinction is easy to overlook. If the suspected crack is above the standing water level, watching the pot with the water supply off may reveal nothing.

4. Check the fresh-water valve connection separately

Dry the accessible area around the float valve's threaded connection, then briefly restore the autofill supply while watching closely. A leak that appears immediately around the valve connection points toward the pressurized supply side rather than a random crack elsewhere in the pot.

Do not aggressively tighten plastic fittings in an attempt to stop a leak. Older plastic can become brittle, and excessive force can turn a questionable fitting into a larger crack. If the connection is damaged or visibly splitting, replacement or professional repair is usually more sensible than continued tightening.

5. Watch for water escaping when the supply is off

With the fresh-water supply shut off, note the water level inside the autofill pot. Because many pots communicate directly with the pool, their water level normally follows the pool level. A falling level therefore needs context.

If both the pool and autofill pot are dropping together, you have established water loss but not its location. The leak could still be in the pool shell, plumbing, autofill pot, or its connecting line. If you can safely isolate the autofill assembly from the pool, a professional can perform more targeted testing of the pot and connecting plumbing.

6. Use dye only around a specific suspected opening

If you can see a suspicious crack below the waterline, calm the water and carefully place a small amount of pool leak-detection dye immediately beside it. Avoid squirting dye forcefully because the resulting current can create misleading movement.

Dye that is repeatedly pulled into one spot can support further investigation, but dye behavior is not foolproof. Circulation, temperature differences, tiny currents, and movement from your hand can all make dye drift. Treat it as a clue rather than final proof.

Cracked pot or leaking supply line?

One useful distinction is whether the problem exists only while the household-water supply is on. If you shut off the autofill supply and exterior wetness stops, investigate the valve, supply fitting, and pressurized feed line. If water loss continues with that supply completely isolated, the pot, pool-side connection, or another part of the pool may deserve more attention.

A water meter can provide another clue. With known household water uses turned off, unexplained meter movement may indicate a pressurized plumbing leak. This test has limitations because irrigation systems, appliances, toilets, and other household fixtures can also use water, so isolate those variables before drawing conclusions.

Do not forget the line between the pot and the pool

A homeowner can inspect the canister and still miss a damaged equalizer line beneath the deck. That pipe allows the autofill pot to share the pool's water level. If it cracks underground, the visible canister may look completely normal while pool water escapes below grade.

This is where professional isolation or pressure testing can become valuable. A leak-detection technician may be able to separate the pot, connecting line, and other pool plumbing so each component can be evaluated independently.

Check overall water loss before assuming the autofill is responsible

If your main concern is that the pool seems to be losing water, turn the autofill off before performing a water-loss comparison. A Mini Bucket Test can serve as a simple first step for comparing normal evaporation with possible leak-related water loss. It does not identify where a leak is located, but the result may help you decide whether further investigation of the autofill, plumbing, pool shell, or other components is worthwhile.

When it is time to call a pool professional

Professional help makes sense when the suspected crack is below the deck, the canister must be replaced, the connecting line needs pressure testing, or you cannot isolate the autofill without altering pool plumbing. Autofill housings are commonly set into or beside concrete decking, so replacing an embedded canister can involve considerably more work than replacing a float valve.

Also get help if the surrounding soil stays wet, the deck shows movement, the water meter suggests a pressurized underground leak, or the pool continues losing more water than expected after the autofill has been shut off.

Bottom line

Checking an autofill pot is mostly an exercise in isolation. Shut off the fresh-water supply, clean and inspect the housing, distinguish pressurized supply leaks from pool-water leaks, and pay close attention to molded fittings and connections. If the canister looks sound but the pool still loses water, remember that the underground line between the autofill and pool can fail without leaving an obvious crack inside the pot.

The goal is not to declare the first suspicious mark a leak. It is to narrow the possibilities methodically so you know whether you are dealing with a simple valve issue, a damaged autofill housing, a buried plumbing problem, or water loss somewhere else in the pool.