Pool Heater Leaking or Making Noise: What's Normal, What's Failing, and What to Do

Nine times out of ten, a little water on the pad is just condensation.But if it's a lot of water clearly coming from the unit, that often points to a failed heat exchanger, which typically means a new heater. Noises sort out the same way: most heater sounds are normal, and a few mean a part is failing. I've been on Florida routes since the late 1990s — my father has been a licensed Florida pool contractor since 1989 — and most of these calls get settled from the pad with a test strip. This page covers leaks and noises only. For a heater that isn't heating, start with our pool heater troubleshooting guide or our heat pump not heating guide.

Leaks: is that water actually a problem?

Heat pumps sweat, and in Florida they sweat a lot

A heat pump's cold coil wrings moisture out of the air like a glass of iced tea in July, and the water drains out through the base pan. Pentair and Hayward both put normal condensation at about three to five gallons an hour while the unit runs, more in humid air. In a South Florida summer that is a real puddle, all day long. It isn't a leak; just keep the drain holes in the base clear. The base pan also catches rain, roof runoff, and sprinkler spray, and on a cold morning frost melts off the coil during defrost. All of that is normal.

The two tests that settle it

Condensation and rain have no chlorine in them. Pool water does.

1. The test strip.Catch water dripping from the heater itself, not the puddle around it, and dip a chlorine test strip in it. No chlorine means condensation or rain. On a bromine pool, use a bromine strip — AquaCal's manual says to test for whichever sanitizer you use.
2. The shutdown test. Turn the heat pump off and leave the pool pump running. Condensation stops when the unit stops. Pentair says water still draining from the base more than an hour after shutdown may mean a leak in the internal plumbing; Hayward and AquaCal say to give it several hours.

One trap: water travels across a pad. A weeping pump seal or backwash water can run under a dry heater and test positive. Follow the wet trail uphill before you blame the heater.

Gas heaters drip too, briefly

Burning gas makes water vapor, and on a cold start it condenses on the cool heat exchanger and drips, sometimes onto the burners with a sizzle. A Pentair commercial manager writing in Pool & Spa Marketingcalled brief start-up condensation normal for most pool heaters, and Hayward says one of its gas models can make a few ounces to a couple of gallons of condensation an hour. It should taper off as the water warms — down here, mostly on the first cold-front start of the winter. One that never dries out is worth a look.

When it is a real leak

• At the unions where the plumbing connects: usually an O-ring or a union that needs reseating, the smallest leak there is.
• At the header, the water manifold on the side of a gas heater: a worn header gasket, which is a gasket repair and one of the replacement items on our heater maintenance checklist.
• From inside the cabinet: water in the burner tray, rust or crust on the exchanger tubes, or chlorinated water from a heat pump that has been off for hours. That's the heat exchanger or the internal plumbing, and usually a replacement conversation.

Hayward lists four reasons a heat exchanger leaks: chemical imbalance, sanitizer damage, freeze damage, and failed joints. Freezes are rare here; the other three are not. Low pH corrodes an exchanger, and chlorine tablets in the skimmer send concentrated sanitizer straight through it — Hayward's HeatPro manual says never do that, and to put any chlorinator downstream of the heater behind a check valve. Hayward also warns that flow above a heater's maximum can thin the tube walls.

If you can physically see the unit leaking, turn the heater off, shut the pool pump off, and call. Running it can make the damage worse.

Noises: what's normal and what isn't

Heat pumps

Normal is a steady fan whoosh, a compressor hum, and a click when the contactor pulls in. The compressor waits a few minutes after a call for heat — three on Hayward's HeatPro, five on Pentair's UltraTemp — and on a cold morning it may stop while the fan clears frost. Neither is a failure.

• Rattling or buzzing:a loose panel or screw, debris in the fan, a pipe vibrating against the cabinet, or a unit not sitting level — the usual suspects on heat pump maker Poolstar's own list. Breaker off, clear the debris, and check for anything loose.
• Grinding, squealing, or scraping: usually the fan motor bearings, or the blade touching the guard or ice. Bearings get worse in stages, the way a pump motor's bearings do. Shut it off and call.
• A loud clank, knock, or screech from the compressor: compressor territory. Shut it off and have it diagnosed.
• A steady hiss with the heat falling off: possibly refrigerant escaping, which is EPA Section 608 work. Our AquaCal guide covers the oily-joint signs of a refrigerant leak.

And confirm it's the heater. The pool pump a few feet away is often the real source of the racket.

Gas heaters and kettling

Normal is the blower spinning up on fan-assisted models, the igniter clicking, a soft whoosh as the burners light, and a steady roar. Kettlingis a popping, rumbling, or banging, like a kettle about to boil, while the heater runs — water flashing to steam against the hot exchanger tubes. Hayward's troubleshooting guide warns that flow below the minimum can boil the water, trip the high limits, and damage the heat exchanger. Two causes:

• Low flow: a dirty filter, packed baskets, a half-closed valve, or a variable-speed pump turned down too low. Rule this out first.
• Scale:South Florida fill water is hard, and high pH, alkalinity, or calcium scales the tubes — another cause on Hayward's failure list. Scale narrows and insulates the tubes, so spots overheat even with decent flow.

Fix flow first. If the banging continues with good flow, shut the heater off and have the exchanger checked for scale. A kettling heater is cooking its own exchanger.

• A boom or loud rumble at ignitionis delayed ignition from dirty burners or a weak spark. Shut it down and get it serviced — that's a safety problem, not a noise problem.
• A sizzlethat fades as a cold start warms up is condensation on the burners. One that won't quit, especially with water under the heater, can be pool water leaking onto the burners. Turn it off and call.
• A whistle or whine is usually water squeezing through a partly open valve or a sticking internal bypass, and less often the gas supply or the blower. Open your valves fully; past that, call a tech.

If you smell gas, none of this applies.Don't flip switches or relight anything. Shut the gas off at the meter or tank if you can do it safely, leave the pad, and call the gas utility. More in our pool heater safety guide.

What you see or hear, what it means, what to do

The homeowner-safe check sequence

Nothing here opens the cabinet.

1. Note when it happens— only while the heater runs, after rain, on a cold start, or at a low pump speed. The timing alone solves a lot of these.
2. Trace the water uphill and rule out the pump, filter, and backwash line.
3. Strip-test water dripping from the heater itself. No chlorine, or no bromine on a bromine pool, means condensation or rain.
4. Run the shutdown test. Heater off, pool pump on. Check after an hour and again after a few hours.
5. Check the unions for a drip right at the plumbing connections.
6. For popping or banging, fix flow.Clean the filter and baskets, open every valve, and raise a variable-speed pump's speed.
7. For rattles, turn the breaker off, clear the top grille and the coil, and look for anything loose or leaning on the cabinet.

Where the homeowner stops

Stop and call when the strip says pool water, when water comes from inside the cabinet, when banging survives a flow fix, or for any grinding, screeching, steady hissing, or gas smell. At Florida's Best Pool Service, heater repairs are managed by us under our Florida Certified Pool/Spa Contractor license. Our own techs handle most of the work; gas-side work goes to a licensed gas contractor, and refrigerant work to an EPA 608-certified tech.

What the repair looks like

A diagnostic runs $0–$125 and is free for weekly-route clients. Most heater repairs land between $250 and $1,800. A failed heat exchanger or compressor runs $4,000–$5,000, and a new heater is $5,000–$7,000 installed, which is why a leaking exchanger on an older heater usually ends in a replacement rather than a repair. An annual heater cleaning or tune-up runs $150–$350, and that's usually when a small weep gets caught. Everything is quoted in writing before a part is ordered. If the strip says pool water or the banging won't stop, book a pool heater repair visit.

Water with no chlorine in it is condensation or rain. Water with chlorine in it is your pool leaving through the heater. One test strip answers most leak calls before anybody opens a cabinet.