# Thread: ??? heating NC indoor pool during winter

1. ## ??? heating NC indoor pool during winter

We have a small inground and indoor pool but are uncertain on the most cost effective method for heating it during the winter. The room has great ventilation for humidity and also has both an elec. room a/c & heater as well as a propane gas stove and ceiling fan. We have placed a solar blanket over the pool when we are not swimming and the water has both a solar and a propane gas heater. The solar must be turned off just before the first freeze here in central NC. So the real question is what's the best pratice for gas heating heating the pool during cold months?

IF we want to swim in 85 degree water in Nov - Apr, do you think it would be cost effective to turn the heater down to say 75 at night and then raise it to 85 degrees during the morning to swim in late afternoons/night OR would it be better to keep the pool heater & pump running at 85 degrees 24 hours a day? I have no idea yet on the cost for operating the pool during the winter as this is a new pool and the first day we have used the heater. It may just be the only month we do so if we find it far too high a cost. Any insight from your knowledge and experience would be sincerely appreciated.

2. Generally speaking, it is more cost effective to only heat the pool just before you are going to use it rather than try and keep it heated all the time. However, if you plan to use the pool very frequently (i.e. every day rather than once or twice a week) then this may not make much difference. It also depends on how quickly you can heat the pool and that depends on the BTU output rating of your gas heater. If you know what that is, then given your pool water volume I can tell you how long it would take to raise the pool temperature by a given amount. For example,

6500 gallons * 8.33 pounds per gallon = 54,145 pounds
1 BTU raises 1 pound of water 1 degree Fahrenheit so a gas heater that was 100,000 BTU/hr would raise your pool 100,000/54,145 = 1.8F per hour
By the way, 9' x 18' x 6' = 972 cubic feet which is 7271 gallons, not 6500 gallons (perhaps the depth is not fully 6' or there are slopes in and other items taking up volume away from the water in the pool).

The fact that your pool is indoors makes a world of difference, assuming you are heating the interior of the room and that the room is reasonably well insulated. Your use of a solar cover helps as well since it is unlikely you are keeping the room at the same temperature as the pool (are you?).

Richard

3. Thanks Richard for the formula and very responcive help. You are right about the size being 7271 gallons but we have few steps into pool and only fill it to 5'9" so I was being conservative at 6500 gallons.

The room is very well insulated with perhaps the exception of heat loss from the windows and the exhaust vent for controlling the condensation. When we are not in the room we keep it set at 65 degrees.

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