Should Softened Water Be Used in Operating a Swamp Cooler?

swamp cooler soft water

On hot summer nights in the early 1900s, people would often sleep on screened-in sleeping porches. Electric fans would pull the outside night air through damp sheets hung to cool the room. That concept, after being refined, became the evaporative cooler (also known as a swamp cooler, desert cooler and wet air cooler) and has been in use for more than 100 years. Although not as popular as air conditioning systems today, millions of Americans still rely on evaporative coolers to reduce household temperatures by as much as 30 degrees.

Is Soft Water OK for a Swamp Cooler?

In areas of the country where swamp coolers are fairly popular (namely dry, desert areas), water hardness is typically quite high –which means many people also own and use a water softener in the home.

We’re occasionally asked if it’s “OK to operate a swamp cooler with softened water?”  So let’s review water softener basics for a moment. First of all, during ion exchange water softening process, calcium and magnesium (minerals that commonly make water “hard”) are replaced by sodium to make water “soft”.  The water has gone from hard to soft, but there is now some salt in the water.  So a water softener trades sodium for calcium and magnesium, you have not changed the total amount of mineral matter going to the swamp cooler, but have exchanged it to a form that may be a bit more soluble.

Mineral Buildup on a Swamp Cooler

An evaporative cooler works by evaporating water in the air stream. If all of the water evaporates, the “stuff” in the water (minerals—calcium, magnesium, sodium) will be left behind. This means that evaporative coolers operating on “hard water” can leave behind calcium scale buildup both in and around the air cooler. And evaporative coolers operating on “soft water” can leave a powdery white residue—sodium. Spraying down or cleaning an evaporative cooler on a regular basis is a lot of work. This work can be minimized by attaching a bleeder hose to your unit.

Bleed the System to Reduce Buildup on an Evaporative Cooler

Make sure your cooler is connected to a “bleeder”. What is a bleeder? At the base of your water pump, there’s usually a small nipple for a 1/4″ plastic waterline. At that point, you can connect a bleeder. A bleeder will siphon off the water to keep the salt from building up in your system. This is especially important if you live in an area with very hard water.  If you don’t bleed off the water but allow it to recirculate through the system, with time, the concentration of salt will build up causing damage to your cooling unit.

If you have a water softener, but live in an area with only “moderately hard water”, you can simply bleed the system a few times a month to drain off the water. This method is preferred as it will save on water usage. When you drain the system make sure the bleed line is drained down the sewer line as the sodium concentration in this water may be too high for irrigation use.

Advantages of Operating an Evaporative Cooler with Soft Water

While operating a “swamp” cooler on softened water isn’t entirely maintenance free, here are some definite advantages to operating with soft rather than hard water:

  • Overall cleaner water circulating through your system.
  • Soft water is better for the cooler’s pump.
  • Reduces the unit’s service and maintenance needs.
  • Reduces problems with biofilm and algae.
  • Reduces scale buildup which can extend the life of the pads on your cooler. (Over time, the cooling pads on a swamp cooler can begin to get clogged by mineral deposits and other matter in the water. This is especially true when operating on hard water).

How Hard is My Water?
Not sure if you have hard water? Download WaterTech’s HARD WATER GUIDE to better understand and recognize the symptoms of hard water and what can be done about it.

Hard Water Guide cta

12 comments

  • I just recently got a swamp cooler, and I am just not sure how to take care of it. I received an instruction manual, but the information is all over the place on that thing. I will definitely try to make sure that I use softer water for the cooler. Hopefully it will extend the life of this cooler! http://www.climatrolact.com.au/our-services

    • No matter the amount of salt it will always cause corrosion. My suggestion would be to try to remove as much of the rust as possible and paint it with Rustoleum paint. This will slow the process but in the next couple or years be prepared to replace it.

  • I have been using soft water in my 15 year old cooler for 2 years now. Although the life of the pads has lasted two seasons, I have noticed a considerable amount of rust, mainly on the squirrel cage and floor of the cooler. Does the salt then, have the same effect on the metal in the cooler as salt does on cars in the Midwest from salted roads? And what can I do to prevent it? Water here is VERY expensive and spilling it out a bleeder would be costly. It there something I can use directly on the metal to protect it? I want to keep my cooler (love the humidity it provides).

    • Colette McCullough

      Hi Angela: Sounds like you may have a problem with your cooler leaking. There is such a small amount of sodium in softened water I doubt it’s the culprit to your rust problem. I would call a water treatment specialist to come out and test your water to make sure you know exactly what’s in your water and/or a hvac specialist to examine your cooler.

  • can you add water softener tablets to the cooler water tray?

    • Colette McCullough

      Sorry, we’re not sure if water softener tablets will do the trick. We recommend calling a local swamp cooler service rep to get their thoughts on this idea. Good luck.

  • We have extremely hard water so now with our water softener we have an extremely large amount of salt buildup in our cooler so we tried a reverse osmosis system for the cooler only but it can’t keep up. Do you think a bleeder when it’s back on the water softener water will take care of the build up or is there a small filter of some kind that we could attach to the water line going to the cooler that would take out some more of the salt?

    • Colette McCullough

      Not sure why the buildup problem. We know water softeners well, but we recommend calling a local swamp cooler service rep with this question about the buildup and bleeder question.

  • Is it possible to run the bleeder line to the nearest sewer vent and let the salty water go into the sewer through the vent?

    • Colette McCullough

      We recommend that you run the bleeder line to nearest drain line. If you want to tap into the sewer, we suggest you check with your local code compliance officer before making any changes.

  • Is rust in the swamp cooler a concern when using softened water? Since soft water systems add sodium to the water?

    • Isaac Linton, CWS I

      Yes. You are in a catch 22. If you don’t soften the water the calcium & iron will build up in the coils. If you use soft water it may leach out the copper and further deteriorate internals of the swamp cooler.