Hot tub leaking: how to find the leak and fix it

Most hot tub leaks are in the equipment bay, at the pump seal, the pump or heater unions, or a valve, and are cheap to fix. To find a leak, turn off power at the breaker, look for water in the equipment bay with a flashlight, and if nothing shows, let the water level drop until it stops. The leak is at that level. Losing up to an inch a week is normal evaporation.

Is it really a leak?

• Normal loss: up to about 1 inch a week, more with long soaks, splashing, or the cover left open.
• Leak: an inch or more a day, a puddle that keeps returning, or wet ground on one side of the cabinet.

To be sure, fill to a marked level, leave the cover on and do not use the tub for 24 hours, then measure.

Where hot tubs leak

Location	What you see	Typical fix	Difficulty
Pump shaft seal	Drip from the bottom of the pump where the wet end meets the motor. Rust or white trails on the motor.	New seal, or a new wet end	Moderate
Pump and heater unions	Drip at the large threaded nuts on each side of the pump or heater	Hand-tighten. Replace the o-ring or gasket.	Easy
Heater assembly	Drip from the heater tube ends, sensor fittings, or element studs	New gaskets or a new heater assembly	Moderate to pro
Slice (gate) valves	Drip from the valve body or around the handle	Replace the valve	Moderate
Diverter and air valves	Water at the top-side valve, or below it inside the cabinet	New o-rings or valve internals	Easy to moderate
Jets	Wet foam behind a jet. Level stops dropping at a jet's height.	New jet gasket or jet body	Moderate to pro
Light lens or housing	Level stops at the light	New lens, gasket, or housing	Easy to moderate
Drain valve	Drip at the drain spigot	Close fully. Replace the cap or valve.	Easy
Manifolds and glued joints	Wet spot in the foam, often far from the equipment	Cut out and re-glue	Pro
Shell crack	Rare. Visible crack with weeping.	Professional repair	Pro

How to find it, step by step

1. Turn off power at the breaker.
2. Open the equipment bay and look with a flashlight. Start at the pumps and heater. Check the underside of every union and the seam where each pump's wet end meets its motor.
3. Feel with a dry paper towel. Wipe under fittings one at a time. The towel shows a slow drip your eye misses.
4. Follow the trail. Water runs along pipes and the floor before it drips. Look for the highest wet point. Mineral crust or rust streaks mark old, slow leaks.
5. Run the test with the pumps on. Some leaks only show under pressure. Restore power, run the jets, and watch from a safe distance without touching anything in the bay. Then turn the power off again before reaching in.
6. If the bay is dry, let the level drop. Mark the water line with tape. Leave the tub off and covered. Check every 12 hours. When the level stops falling, look around the shell at exactly that height: jets, lights, and fittings at that line are the suspects.
7. Use dye. With the water still, squeeze a little food coloring near a suspect jet or fitting. Dye that gets pulled into a gap confirms the spot.
8. Check the other panels. Remove side panels where you can. Wet or discolored foam points to the nearest plumbing.

A useful shortcut: if the tub leaks only when the pumps run, the leak is on the pressure side, after the pump. If it leaks all the time, it can be anywhere below the water line.

Fixes an owner can do

Unions

With power off, tighten the union nut by hand. If it still drips, close the slice valves on both sides if your tub has them (or drain below that level), unscrew the union, and replace the o-ring. Seat the new one in its groove with a smear of silicone lubricant made for spa o-rings, and hand-tighten. Do not use a wrench with force. Cracked union nuts are common from overtightening.

Drain valve

Make sure it is fully closed and the cap has its gasket. Replacement drain valves are inexpensive.

Diverter and air control valves

The cap usually unscrews by hand with power off and the water level below the valve. Replace the o-rings and lubricate them.

Light lens

Many lenses thread into the housing from inside the cabinet or the tub. Replace a cracked lens or flattened gasket.

Fixes that usually need a pro

• Pump seal. The wet end comes apart and the seal is pressed in. Some owners do this, and a complete replacement wet end is often easier. Because a leaking seal drips onto the motor, do not delay. Match the wet end to your pump using which hot tub pump do I have.
• Heater leaks. The heater connects directly to the control box wiring.
• Jets and manifolds buried in foam. Finding and reaching them means digging out insulation, then re-gluing PVC.
• Anything that has wet the control box.

For those, get bids from local pros.

Leaks and electricity

Water plus 240V equipment is the real hazard. If a leak is near the control box, pump motors, or ozonator, or the breaker has started tripping, turn the tub off at the breaker until it is fixed. See hot tub tripping breaker.

Leaks in winter

If the tub must stay running in freezing weather while you wait for parts, keep topping it up above the jets so the pumps do not run dry, and check it daily. If you cannot keep up with the water loss, the tub needs to be drained and winterized properly, not just emptied.

Preventing leaks

• Keep pH at 7.2–7.8 and sanitizer in range. Low pH and very high chlorine eat seals and gaskets.
• Do not let pumps run dry.
• Check the equipment bay monthly for drips.
• Hand-tighten unions after the first few heat cycles on a new or refilled tub.

Parts for most of these repairs are in plumbing parts and pumps.