Swamp Cooler Freeze Damage Repair: Float Valves, Supply Lines, Pumps and Bleed Lines

When water freezes it expands by about 9% in volume. In an open pan that just lifts the ice. In a closed space such as a 1/4 inch supply line, a float valve body, a pump volute or a bleed tee, the ice has nowhere to go, and the part splits. Almost all swamp cooler freeze damage happens in these few small parts, and almost all of it is repairable with inexpensive replacements. The hard part is finding every crack before it leaks onto your roof or ceiling.

This page walks you through inspecting a cooler that froze with water in it, pressure testing the supply side, and repairing each common failure. If your cooler has not frozen yet, see how to drain a swamp cooler to prevent it.

Where freeze damage happens, ranked by likelihood

The supply line and float valve account for most freeze calls, because they stay pressurized and are the smallest, most exposed water spaces on the cooler.

Before you start: safety and thawing

1. Close the supply valve. If water is already leaking anywhere, shut it off first and check below the cooler for water entering the house.
2. Kill power to the cooler. Water and a split line around a 120 V pump and motor is a shock hazard. Lock out the disconnect or breaker.
3. Let everything thaw. Wait for a day above freezing, or warm the lines gently with a hair dryer. Never use an open flame or heat gun on plastic tubing, float valves or near the cooler cabinet and roof.
4. Check inside the house. Look at the ceiling around the cooler diffuser and in the attic near the duct for stains or wet insulation. If drywall is wet, dry it quickly; the EPA advises drying water-damaged materials within 24 to 48 hours to prevent mold growth.

The pressure test: find every leak in 15 minutes

Ice can seal a crack temporarily. A part that looks fine frozen may leak hours after it thaws. Do this test once everything is fully thawed.

1. Open the cabinet and leave power off. Remove a side panel so you can see the float valve, pump and bleed tee.
2. Put a dry paper towel at every joint. Wrap or tuck one at the supply valve outlet, any unions along the line, the line entry into the cabinet, and the float valve inlet. A drip shows up as a wet spot even when you miss it by eye.
3. Open the supply valve a quarter turn. Slowly, so a split line does not spray. Walk the line from the valve to the cooler, looking and listening.
4. Watch the float valve fill the pan. It should fill smoothly and shut off completely when the float rises. Seeping water around the valve body, or a valve that will not shut off even with the float lifted by hand, means the valve is cracked or the seat is damaged.
5. Open the valve fully and wait 10 minutes. Recheck every towel. Many hairline cracks only leak at full pressure.
6. Restore power and run the pump only. Watch the volute, tubing, spider and distribution trough for leaks. Check that water flows to all pads and out of the bleed tube.
7. Check the drain. Pull the standpipe and confirm the pan drains at a normal speed. Slow drainage means an ice plug or partially collapsed hose.

Repairing a split supply line

Copper tubing

Frozen copper usually splits lengthwise, an inch or several inches long, often near a bend, a low spot or a fitting. The tube around the split may be visibly swollen.

1. Find the extent of the damage. Run your fingers along the tube for bulges. Copper can be stretched beyond the visible split.
2. Cut out the damaged section. Use a small tubing cutter, cutting at least 1 inch beyond any swelling on each side. Deburr inside and out.
3. Splice with compression unions. For a short gap, use a 1/4 inch compression union at each end with a new piece of 1/4 inch copper or poly tubing between them. Slide on the nut and ferrule, insert the tube fully, and tighten finger tight plus about 3/4 turn.
4. Replace instead if the line has multiple splits. A full new run of 1/4 inch tubing from the valve to the float is often faster than three splices and removes hidden damage.
5. Pressure test the repair. Repeat the paper towel check at each new fitting.

Polyethylene or vinyl tubing

Plastic lines may crack or simply develop white stress lines that later fail. Freeze-stressed plastic tubing is not worth splicing. Replace the run end to end with new 1/4 inch tubing rated for potable water pressure, using new ferrules and plastic inserts where the fittings require them. For line materials, routing and freeze-resistant layouts, see water supply and drain lines.

Valves and saddle taps

Supply valves in an unheated attic or outside wall can freeze too. A cracked valve body leaks at the stem or body seam. Replacing a valve on a household water line is a plumbing job; if you are not comfortable shutting off the house water and working on supply piping, call a plumber. Saddle valves that pierce a pipe are particularly prone to leaking after a freeze and are worth replacing with a proper tee and quarter turn valve.

Replacing a cracked float valve

Float valves for coolers are inexpensive universal parts. Do not try to glue a cracked plastic body.

1. Shut off water and kill power.
2. Disconnect the supply line. Hold the valve with one wrench and loosen the compression nut with another.
3. Remove the valve. Unscrew the jam nut on the inside or outside of the cabinet wall and pull the valve out. Note its height and how the float arm was oriented.
4. Install the new valve. Use the supplied washers on each side of the cabinet wall, snug the jam nut, and reconnect the line with a new ferrule if the old one is deformed.
5. Set the water level. Adjust the float arm so the pan fills to about 1 inch below the top of the overflow standpipe. The details are in float valve adjustment.

Burst pump housings and frozen bleed lines

Pump

A recirculating pump left in the pan with water inside its volute can crack when the pan freezes. Inspect the volute (the snail-shaped housing around the impeller) for hairline cracks, check that the impeller spins freely by hand, and look for water inside the motor housing. Then test the pump in a bucket of water, plugged into a GFCI-protected outlet. If it hums but moves no water, trips the GFCI, or leaks from the housing, replace it. See how to replace a swamp cooler pump for the swap, and choosing a replacement pump to get the right GPH and fit.

Bleed-off line

The bleed-off tee sits in the pump discharge line and sends a small, continuous stream to drain. Its narrow passages are among the first to freeze. Signs of damage are a cracked tee, a split tube, or no bleed flow when the pump runs. Replace the tee and tubing, which are inexpensive. Then confirm the bleed rate is right for your water hardness; bleed-off and water quality explains how to set it.

Hidden damage most people miss

• Ceiling and attic water. A slow leak from a split line can run down the duct exterior into the attic. Look for stains on the ceiling around the diffuser and dampness in insulation near the duct.
• Pan seams and rust. Ice in a pan that was not fully drained can open existing rust or seam weakness. Inspect corners and seams; cabinet rust and pan repair covers sealing and patching.
• Roof penetration. Ice dams around the cooler stand or curb can push water under flashing. If you see stains away from the duct, have the roof checked.
• Pads frozen solid. Aspen pads that froze wet often slump and tear when they thaw. Rigid media can crack. Inspect in spring and replace as needed.

Preventing it next year

Every repair above traces back to water left in a closed space. Next fall, close the supply valve before the first forecast low of about 34 F, drain the line from the float valve, empty the pan and pump, and pull the bleed tube. Check when to winterize by region to put the right date on your calendar, and see the winterizing overview for the full shutdown.