Running Pools during winter

We manage a number of apartment communities in Colorado, do to marketing purposes we keep pools open through the winter at considerable gas costs.

It's always been my understanding not to run at temps too low due to problems with condesation in the heaters. Have always used 65-70 degrees as rule of thumb.

Looking at the owner's manuals it would seem we can run them down around 70 degrees (Pentair MegaTherm) and a Raypak - 406A doesn't list a minimum temp but claims to have unitherm bypass to control condensation.

Contractor recently advised to keep them at 82 degrees (Gas Bill!!!) Looking for thoughts on best practices, ways to save on gas but still keep the pools open and not in great risk of freezing w/ an overnight pump or heater shutdown problem.

Call the makers, but you can almost certainly install a bypass loop around the heater, with valves on BOTH the heater side and the bypass side.

Start off by throttling the valve on the heater side, till you have flow at the minimum. There's probably either a flow switch or a pressure switch which will turn off the heater when flow gets too low.

Then gradually turn the heater setting down, 5 degrees at a time. At each point, check the OUTFLOW (effluent) from the heater to make sure it is above the minimum temp. An insert thermometer is best, but you can probably use your hand . . . IF you have a bucket filled with 80 degree water for comparison.

So long as the effluent temp is OK, and you have sufficient flow, I'm pretty sure you'll be able to avoid condensation problems . . . IF you have an electronic ignition heater.

If you have an old heater with a standing pilot, this may not work, since the moisture from the pilot flame can cause problems.

(REMEMBER TO OPEN THE HEATER VALVE BACK UP DURING NORMAL OPERATIONS. You don't want to have 120 F water in the heat exchanger during warm weather.)