Indoor Pool Humidity Problem

by Ron
(New England)

The heated pool water is 80 deg. the room tempature is 76 deg. The windows are steamed over all the time and moisture is dripping from the ceiling and heat ducts.

We put a big dehumidifier in and we have it set at about 21% humidity. What coud be the problem!

Thank you for any help you for any help or advice you could give.


Thanks for the question Ronald

I take care of the YMCA indoor pool (80,000 gallons) so I have first hand knowledge about the importance of heating, humidity, exhaust, and fresh air flow of an indoor pool.

In my opinion, the most important factor between an indoor pool vs. an outdoor pool is the exhaust and fresh air flow.

If you don't have them the humidity will rapidly rise in the room causing mold, mildew, and the moist air will find itself into the walls, ceiling and attic of the house causing more problems down the road.

We replaced all the roof tiles in the pool room at the Y because of this very issue. Rust, water damage, and mold because the system went down."

The main thing that I've found when dealing with humidity and indoor pools is "fresh air in and exhaust out". Many times homeowners have the exhaust, or de-humidification, but not the fresh air coming in. This could be the problem. Check to see what your fresh air flow is. The other parts are important as well, but air intake and exhaust are the biggest.

They give air flow rates and charts. It's pretty dry reading, no pun intended, but gives much information. Many times pool owners have this problem in the Fall through Winter, but not much during the Summer. Sometimes this is dependent on where you live.

In Virginia, where I'm from, the Fall and Spring were easier than the Summer. The humidity in the Summer can get to 95% while the Fall and Spring can dip to 40 or 50%.

Remember that you're pulling outside air inside the facility. If the outside ambient air is humid, and inside dehumidifier will need to work harder at keeping the moisture down.

There's an entire balancing act for having an indoor pool - fresh air, exhaust, cooling, room heating, pool heating, etc... I would first check the fresh air intake and exhaust, read the literature above, and go from there.

Hope this helps and let me know how this turns out for you.


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Indoor Pool Shut Down Question

What is the best way to maintain/close an indoor pool while away for the winter months?

The pool is a vinyl 12 x 24 in a detached, heated structure with a chlorine generator and a cover located in Northern Illinois.

Should I lower the temperature on the pool heater and the room and let the pump run for a couple of hours a day?

Is it best to have someone add chemicals regularly or is it safe to walk away and hope for the best.

Thank you for your time.

Thanks for the question

For the best way to close a pool for the Winter you can go to this post:

Pool Winterization

Obviously you can either winterize the pool or not, so here are my thoughts on the subject.

There are some variables that you need to consider.

Are there any lines that can be frozen? If there's even the slightest chance of that, you should winterize the pool. If there's a chance that anything can be frozen, you should close the pool.

On the other hand, if you can have someone who knows about pools to take care of you pool, and there's no chance of frozen lines, that would be the route to go. If your not going to be using the pool, I'd lower the temperature of the room as low as it can go, without freezing the room.

When I had my pool route in Arizona, the water temperature went down into the high 30s - low 40s. A little cold to be putting you hand in to test chemicals, but the water wasn't frozen and the circulation was fine.

Closing an indoor pool is not different than closing an outdoor pool.

The main thing to remember is to remove and salt cell and blow the lines out if you plan on closing the pool.

So if you can get away with having some who is responsible and knows about pools to take care of it during the Winter, I'd do that. There's really no reason to get an expensive pool cover. You can get a nice inexpensive solar cover, cut it to match the shape of your pool, and leave it on all Winter. Add the chemicals when needed.

Swimming Pool Solar Covers

The water still needs to be tested weekly to ensure proper water chemistry.

Swimming Pool Chemistry

For a controlled environment like an indoor pool, 3 - 4 hours of filtration during the Winter months is fine.


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Best combo/heater/dehumidifier for a residential indoor pool

We have purchased a home with an indoor pool that has an old Dryatron(circa 1979) system used to heat/dehumidify the indoor pool room and also heat the water. It works pretty well but costs a small fortune.

We have decided install a separate natural gas fired pool heater to take care of heating the pool but do not know what kind of unit to use that will heat and dehumidify the room itself. The room is about 40 feet long by 20 feet wide.Any thoughts would be so appreciated! Tring to enjoy the pool but rein in some of the costs!

Thanks so much!

I'm familiar with the DryaTron. The YMCA in Oregon had one and that's where I was the pool operator. For good brand names you can try Hi-E Dry and Ebac. Both of these can be found on You always want to go a bit larger than needed for your size room. A larger unit can always be dialed down.

You also want a unit that has optimal Cubic Feet per Minute (CFM). For the cost, a good ballpark figure would be around $700 per 400 sq. ft.

Hope this helps.


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