I did it: A/C condensation saved for pool

[BowserB]

I've thought about this a long time. Researched lots of info on uses for the condensate from central air evaporators and dehumidifiers. No it's not suitable for drinking but is for watering plants OR for topping off your swimming pool. Check out for yourself the health and safety issues. Even the CDC is good with it. Here in the Gulf south (greater Houston area) it gets hot and it gets humid and mostly stays that way for a lot of the year. In addition to two A/C units--downstairs and up, I have a whole house Aprilaire dehumidifier that is independent of the two A/C systems (although it could be integrated if I had so opted--long story.) So three machines creating H2O condensate. So I finally did it--or rather the A/C guys did it. My downstairs AC and the dehumidifier, instead of going to the drain and the sanitary sewer, are draining into a rain barrel. My upstairs unit was too far away to easily and reliably connect to the pipe going outside. A faucet on the rain barrel connects a hose to the pool. It's a 40 gallon barrel, so I don't have to have the hose there all the time.

Right now I'm collecting first, then to the pool. We're in a fairly mild part of the year, but for the first five days, I've collected about 5 gallons of condensate per day. The pH of this water is 5.8 or so. Why, you ask, is it not 7.0? The process of air blowing over the evaporator coils as the water condenses causes carbon dioxide to be dissolved in the water. (Human skin has a pH of 5.5. Coffee 4.9, fruit juices range from 3.3 to 4.3.) I was hoping the low pH condensate would, in addition to compensating for evaporation, save having to add muriatic acid to the water. Not sure what 5 gallons a day will do for a 15,000 gallon pool. During warmer times of the year, according to local A/C people, I'll probably see 10 gallons a day or more. The AC guys said if both AC unit plus the dehumidifier were connected, I could get between 12 and 20 gallons a day in the summer.

My cheapskate friend asked, "How long will it take for savings on city water plus savings on muriatic acid to pay for the rerouting of condensate?" I don't expect a rapid payback or maybe never get my money back. I'm not an environmental nut, but I am happy to conserve when I can. Even with my current minimal 5 gallons a day, I'm saving 150 gallons a month. There are 10 million private swimming pools in the U.S. If only half are in a climate where they could do what I just did, that's 750 million gallons of water PER MONTH. 9 billion gallons of water per year. Free. Plus sum amount of muriatic acide savings. And that's based on my autumn savings of 5 gallons a day, which may double in the summer.

 

[JoyfulNoise]

I would urge you to have the water tested by an independent lab before you start adding it to your pool. There are many scholarly articles on the reuse of condensate water for various technical applications and most of them conclude that it is unusable except for non-edible landscape water. Condensate water is very acidic and it runs over many metallic components in the A-frame evaporator of an HVAC system. The A frame contains copper, aluminum and galvanized iron components as well as solder brazes that contain tin and, depending on the age, possibly lead. The condensate water leaches metals and so that can make it unsuitable for many applications. Only by having it tested can you know what you’re adding to your pool.

 

[BowserB]

Will do.
Thanks.

 

[pjt]

The condensate water leaches metals and so that can make it unsuitable for many applications.

Would harvesting the condensate from a heat pump also have the same problems?

 

[JoyfulNoise]

Would harvesting the condensate from a heat pump also have the same problems?

Yes. The heat exchanger tubing that rejects heat (condenser) into the pool water is titanium but the evaporator coil that absorbs heat from the air (and cools it) is copper/aluminum.

 

[JoyfulNoise]

A more interesting use of the water would be to setup misting lines around the condenser and the have a water misting pump turn on with the condenser compressor to mist water into the heat exchanger. Water droplets that evaporate off the condenser coils would absorb much more heat than the air that flows through the heat exchanger because the latent heat of vaporization is much larger than the heat capacity of dry air. So, in essence, you'd create more efficient liquefaction of the coolant and reduce the power load on the compressor. I've read a few posts on HVAC forums about people doing this and there is a measurable boost in efficiency but it does require a substantial amount of water. You also want to make sure that you neutralize the acidity of the misting water use so as to not damage the heat exchanger or internal plumbing.

 

[JoeSelf]

A more interesting use of the water would be to setup misting lines around the condenser and the have a water misting pump turn on with the condenser compressor to mist water into the heat exchanger. Water droplets that evaporate off the condenser coils would absorb much more heat than the air that flows through the heat exchanger because the latent heat of vaporization is much larger than the heat capacity of dry air. So, in essence, you'd create more efficient liquefaction of the coolant and reduce the power load on the compressor. I've read a few posts on HVAC forums about people doing this and there is a measurable boost in efficiency but it does require a substantial amount of water. You also want to make sure that you neutralize the acidity of the misting water use so as to not damage the heat exchanger or internal plumbing.

Be careful of this, it does reduce the temp around the condenser, but it changes the way the unit operates. Videos i've seen caution this as it could shorten the lifetime of the condenser. You also have to consider any build up of minerals on the fintube or fingers (looks like tinsel) if you have a TRANE unit.

 

[BowserB]

I would urge you to have the water tested by an independent lab before you start adding it to your pool. There are many scholarly articles on the reuse of condensate water for various technical applications and most of them conclude that it is unusable except for non-edible landscape water. Condensate water is very acidic and it runs over many metallic components in the A-frame evaporator of an HVAC system. The A frame contains copper, aluminum and galvanized iron components as well as solder brazes that contain tin and, depending on the age, possibly lead. The condensate water leaches metals and so that can make it unsuitable for many applications. Only by having it tested can you know what you’re adding to your pool.

Tests done. -0- lead, -0- copper, -0- iron. Maybe because our A/C and house are only five years old and modern city codes apply to materials? CDC just advises treatment of the water for potable water applications due to bacteria and virus concerns. Luckily we have a water treatment already in use (6 ppm of chlorine.) The acidity doesn't seem too serious at pH 5.8 compared to human skin at 5.5, or club soda at 5.2. NIH rates a pH of 6 down to 4 as "minimally erosive" 4-3 as "erosive" and 3-2 "extremely erosive." 5.8 is not dissolving much of anything to my thinking. I'm using it. If it turns out to be a mistake, I'll report back here.

 

[duraleigh]

TFP considers pH of 6.8 as beginning to get "agressive". I think you may find it will be too late
"if turns out to be a mistake"

 

[JamesW]

The water is basically equivalent to distilled water.

It should not leach too much metal from the equipment because, if it did, the equipment would fail pretty fast.

Any trace amounts of metals should not be enough to matter.

I don't think that lead is still used in any significant degree.

 

[JoyfulNoise]

Tests done. -0- lead, -0- copper, -0- iron. Maybe because our A/C and house are only five years old and modern city codes apply to materials? CDC just advises treatment of the water for potable water applications due to bacteria and virus concerns. Luckily we have a water treatment already in use (6 ppm of chlorine.) The acidity doesn't seem too serious at pH 5.8 compared to human skin at 5.5, or club soda at 5.2. NIH rates a pH of 6 down to 4 as "minimally erosive" 4-3 as "erosive" and 3-2 "extremely erosive." 5.8 is not dissolving much of anything to my thinking. I'm using it. If it turns out to be a mistake, I'll report back here.

Great job getting the analysis done … better safe than sorry.

I agree, modern units should not have any lead brazings in them. I have much older units so I wouldn’t be surprised at all if mine used lead/tin solders.

If the acidity is too much it’s easy to solve - you can run the condensate water through the neutralizing filter (crushed natural granite chips). It will bring the pH back up to the 7’s and add only minimal amounts of CH and carbonate alkalinity.

A friend of ours has a 1200 gallon storage tank that is fed from his flat roof (we have lots of flat roof construction around here) and his AC unit is on the roof. He runs the condensate line to the gutter that collect the rain water and both are used to fill his tank. This year we got a bunch of good rain storms and his tank was filled multiple times to the point of overflowing. They don’t have a pool but use the captured water for their raised bed vegetable garden as well as their fruit trees. It’s a very slick setup and even has fully automated irrigation controls with a tank pump to deliver the water to his drip lines. They’re big on growing their own food and eating natural so they really went all out on it.

 

[JamesW]

The pool water will always be in the correct pH range and adding condensation water should not affect anything.

It's basically reverse evaporation equivalent to adding the same water that evaporates.

 

[JamesW]

How did this happen where the pH went down and the TA went up with nothing added?

 

[JamesW]

A heat pump can produce about 3 to 5 gallons per hour.

As long as the TA is good, the pH should never be at risk from a trickle of distilled water.