Why do swamp coolers leak in spring?
Because they spend the winter dry. A cooler drained and covered in October sits through five cold months, and gaskets stiffen, the float valve sticks, rust spots in the pan spread and a line that was already weak can split. Turning the water back on in March finds all of it at once.
A sensible start-up is ten minutes of watching. Turn the water on, let the pan fill, and check that the float shuts off at the right level and that the overflow pipe is not carrying a steady stream. Then look at the roof around the curb and the stucco below it before you walk away.
Fall shut-down is the other habit that matters. A unit that was not fully drained and covered can sit all winter with a line, a pan or a valve already damaged, and it shows nothing until the water comes back on in spring. The swamp cooler and AC leak guide goes through the start-up and shut-down routine in order.
What actually fails on a cooler?
Four parts, mostly. The float valve that is supposed to stop the filling, the small copper line that feeds it, the overflow pipe meant to carry excess away, and the pan itself, which corrodes from the inside where hard water leaves scale. Any one of them puts water on your roof.
Hard water is the common thread. Phoenix tap water is among the hardest of any large US city, and a cooler pan concentrates those minerals further as water evaporates out of it all day. Scale builds on the float mechanism and the bleed-off line, and the pan's metal gives up at the seams and around fittings.
None of those repairs are ours, and that is worth being clear about rather than vague. A cooler or HVAC technician replaces a float valve, a line or a pan. What the technician on our crew does is tell you which part the water appears to be coming from, with photographs, so you are not guessing when you make that call.
How is a cooler leak different from an AC leak?
A cooler leaks supply water under pressure, or a pan full of standing water. An air conditioner only loses the water it condenses, a slow trickle by comparison. That makes cooler leaks bigger, faster and dirtier, because cooler water has been sitting in a pan with mineral scale, dust and whatever blew in.
The practical difference shows up in what leaves the house. A clean condensate leak caught early can sometimes be dried with the insulation left alone; pan water that has soaked insulation and carpet pad means that material is bagged and removed instead.
Houses with both systems get both problems at different times of year. Condensate leaks cluster from May to September, cooler leaks in March and April and again in October, so a dual-system house really has two separate seasons to watch.
What about the roof around the cooler?
It gets looked at, because a leaking cooler wets the roof it sits on. On a low-slope or foam roof, water pooling at the curb softens the coating and can work into the deck beneath. The cooler technician handles the unit, a roofing contractor handles the roof, and the crew dries the inside.
Curbs and flashings are a weak point by design: a hole was cut in the roof to fit the unit, and the seal around that hole is decades old on most of these houses. Water from the pan runs right across it.
That is why a cooler leak and a roof leak are sometimes the same event with two causes. Monsoon wind also damages cooler housings and covers, which opens another path into the same hole.
