Things You'll Need
Never repair or work with your unit before first assuring that the power to the unit is off.
Evaporative swamp coolers are an energy efficient way to cool a house in dry climates. Unfortunately, as with most household appliance, things can go wrong. If your cooler leaks water onto your roof, not only might you have to replace your cooler, but you may also have to replace your roof as well. Unless the cooler has been physically damaged, there are only six places that your cooler can be leaking from. We will run through these places one by one. Here are some simple ideas on how to diagnose and fix your leaking swamp cooler.
Check the water feed line. A common leak encountered on evaporative coolers is at the point where the 1/4-inch copper water line enters the cooler housing. The three most likely problems here are: 1) the compression nut needs tightening 2) the rubber gasket (washer) needs to be replaced, or 3) the float valve inside has broken or come loose and needs to be tightened or replaced.
Inspect the float valve inlet. If the water leak seems to be coming from the water inlet at the float valve, you problem could be that the water entering your reservoir is spraying outside your reservoir. Lift up on the float arm to determine if all of the water spraying out sprays into the water reservoir. If not, simply adjust the float valve to point further away from the edge of your reservoir.
Check the front of the cooler at the pad. This common problem results in serious damage to the front screen cover of the cooler as rust and scale buildup slowly destroys it. This type of leak will usually be the result of one of three problems. 1) The top of the pad is so caked with scale that the water sprays off of it. 2) The front of the pad is so caked with scale that mini-stalactites have formed a bridge between the pad and the front screen of the cooler, which will allow water to run freely out of the front of the cooler. 3) The distributor housing is warped and no longer forms a snug fit over the top of the cooler pad, which will allow the water to spray or squirt out. Any of these three problems will involve replacing either the pad itself or the distributor housing.
Inspect the drain hole on the bottom of the cooler. If water is leaking out of the drain hole, then you most likely have a rather simple fix. Check to see if the reservoir's water level is above the top of the overflow pipe. If so, simply bend the float arm to adjust the water level. If not, check to see that the overflow pipe is screwed securely into place in the drain hole. If so, then you may need to replace the drain fittings and/or the overflow pipe.
Check to see if there is leaking out of the bottom of the cooler housing from the sides of the pad. If this is the case, check the level of scale buildup on the sides of the pad and on the plastic inserts on the sides. If it seems excessive you need to either clean the pad or replace it. If the level of scale buildup doesn't seem excessive, check to make sure that the plastic side wall of the reservoir assembly is seated properly, with the base inside the wall of the lower reservoir. Also check to see if this plastic side wall is cracked or has a hole in it.
Inspect the area at the bottom of the cooler housing from under the water reservoir. Attempt to tighten or even replace the drain fitting as this will be your most inexpensive possibility for a solution. Make sure the water isn't overflowing the front or back of the reservoir, if so simply adjust the float valve. More than likely, your plastic reservoir liner is cracked and needs to be replaced. This will cost less than replacing the pad, but can be a rather major task, though it's not as difficult as it sounds. See step 7 for a quick walk through to replace this reservoir liner.
Remove the drain assembly and overflow pipe. Remove the pad, water distributor (this can be set on top of the cooler), and the water pump (this can remain hooked up to the distributor). Turn off the power and water to the unit. Unscrew the float valve from the side of the cooler. Remove both plastic side walls as well as the brace at the bottom which seats the pad in place. Now remove the large plastic reservoir liner which holds all of the systems water. You will most likely buy a new reservoir liner along with both plastic side walls.