Why is My Swamp (Evaporative) Cooler
Blowing Hot Air?
This is one of the questions ALL
swamp cooler owners eventually ask at some point
...at least once a season, or
...perhaps several times a season.
This page will cover as many reasons as I can think
of for an evaporative cooler NOT to blow cool air.
Humidity Outside of Your Home
Before grabbing that ladder and climbing onto your
roof.... What is the relative humidity outdoors?
Has it been raining for three days and you feel like
you're living in the tropics?
Evaporative coolers work at their best in dry
weather. If it is humid outside, forget about
Use this handy chart below to determine if humidity
is the reason. You will need an indoor
thermometer. Outside readings for your region
can be found online or on most smart phones.
Example: As I write this, the current
temperature in El Paso, TX is 82 degrees. The
relative humidity is 31%. According to the
chart, my inside temperature with my swamp cooler
on, should be about 71 degrees. My indoor
thermometer reads 73 degrees. Off by 2
degrees. Not bad for late in the season when
my pads have more scale build-up and my water tube
holes are partly clogged.
used to determine what temperature should be inside
with a swamp cooler based on
the relative humidity and temperature outside
Is Your On / Off Switch Turned on Fan (Vent)
Many swamp coolers have two main settings.
A fan (vent) setting and a cool setting.
The cool setting turns the pump on at the
same time. Inside your cooler, the
pump is pumping water to your pads and the
blower is pushing cold air into your home.
If only the fan (vent) is on, then you are
just blowing the outside air into your
house. If it is 95 degrees out, that
is what you are going to have inside your
Typical on-off controls for evaporative
So what is the point of the vent
feature? I use the fan (vent) feature in the
evenings to blow fresh dry cool air into the house
when the temperatures drop into the low 70's and
60's. Sometimes it is just nice to have air
moving around the house. Since it is cooler, I
don't need the pump on blowing moist air.
Delivery System. Is Everything Functioning?
The swamp cooler needs water flowing over
some type of pad. No water = Hot air.
How it Works
a) Water goes through a water line (copper
tubing, poly tubing, a hose, etc)
b) The water flows through a float valve on
the side of the cooler into a basin
c) A pump sitting in the basin pumps water
through a tube to the pads
d) The water drips off the pads back into the
e) When water evaporates more water comes
through the waterline.
f) The float valve regulates the level of the
water in the basin cutting off the water until the
basin level drops again, ........and again, and
- Is the water turned on?
- Is the water flowing through the tubing or hose?
- Is the water tube connected to the cooler?
- Is the water flowing into the basin of the cooler?
- Is the water high enough in the basin for the pump
to suck up the water?
If yes, to all above then......
- Is the
pump pumping water to your pads?
- Is enough water being pumped to the pads
If yes, to all above then go to water distribution
If no, then you might need to buy a new pump. First
check the tube that goes from the pump to your water
distribution system to make sure it is not clogged.
Sometimes sediment or chunks of hard water scaling
get lodged inside the tube blocking it. Clean
Did the pump fall over into the water basin and get
wet? The top part of these pumps need to stay
dry. Only the bottom portion of the pump goes
in the water. If the top part of the pump got
soaked, toss it, so you don't electrocute yourself.
Did you or someone buy the cheapest pump available
that did not have enough horse power to pump water
to your pads? Before you buy a pump make sure
it is powerful enough for your cooler. You
will have to do some research. If your not
sure, have your cooler brand and model number
written down before you visit the hardware store.
In swamp cooler regions, the big box stores carry a
variety of pumps that cover most coolers.
Water Distribution Tube/Pipe
The water travels from the pump through a tube to
some type of housing that contains some type of
tube/pipe that sprinkles, dribbles, oozes, the water
over your pads.
The water distribution housing of my cooler holds a
pvc pipe with holes in it. That is it.
The problem with this PVC pipe is that, in hard
water regions the pipe gets clogged. It needs
to be cleaned at the end of every summer.
Sometimes, in the middle of the summer season also.
You need to poke something in the holes to open them
up. Run a coat hanger through the inside to
scrap off residue. You can also soak it in
vinegar for a few days to soften the hard water
If your tube/pipe is so clogged up that you cannot
get anything through the holes to clear them, you
are probably better off just buying a new tube.
Unless you have weeks to soak it in vinegar.
Screw driver used to unplug the holes.
Cleaned up water
distribution housing with gray water delivery tube
attached on the other side
The gray tube attaches to the pump. The whole
housing (black thing) sits on top of the pads.
Cooling Pads or Media Need to be Replaced?
If the water, pump, and your water
delivery tubes are all functioning properly, the
problem could be your cooling pads.
The type of cooling pads my cooler uses
are the paper waffle things shown below. They
are called cooling media. To me they are paper
waffle things that are a pain in the ass to carry
onto the roof. When I am discarding them, I
drop them off the roof to watch them break into
pieces. Easier to throw away when the pieces
If your cooler uses this type of cooling media it
should be showing some brown color. If it is
totally white and hard as a rock it is time to buy
new pads. The white scaling will not come off
without the paper breaking off. In a hard
water area expect to only get 2-3 years out of these
In other words, if your pads can no longer soak up
and hold water, you will not have cool air.
When I winterize my swamp cooler
(see how to do this here...) and notice
that my pads are shot, I order them online from the
Home Depot during the winter and store them until I
need them in the spring. These are a seasonal
item so you will only see them in stock during late
spring and summer in the big box stores. So if
you need to replace them mid-season you should have
no problem finding them.
Swamp cooler pads
after only 2 months of use. A little scaling.
5) Are All of
the Access Doors on the Cooler Closed?
If a door or a piece of your cooler
housing is open, you are not going to have cool air.
The cooler works in a box. If the box is open,
the cool air goes out the hole and not into your
house. All you get is warm air.
In August of 2016, my cooler was blowing warm air.
When I climbed up on the roof, I discovered why.
A previously damaged access panel had blown open
during some high winds
this panel here...). I reattached
it. Placed bungee cords around the cooler to
keep it on. Ordered a new panel and replaced
the damaged panel.
For information on how to
prepare your cooler for winter, please go to this
For information on float
valves and how to install them, please go to this