Steam Coming from Spa Heater


New member
Aug 19, 2016
Gilroy, Ca
Just started my spa heater after a few months of not using it. Noticed significant amount of steam coming from it. Ran it for 10-15 minutes to see if it would dissipate and didn't seem to. I have never noticed this before, so I think it's new.

3 things recently happened between now and the last time we ran the heater:
1) We had our gas meter upgraded to a larger size.
2) We have had significant rain.
3) It has been cold here, dropping down to freezing a few nights. (I'm in California, so this is not normal). We don't winterize the pool so I'm wondering if this did something to the heater...
I don't see any sign of leaking water around or under the heater. All fittings at the pool equipment seem in good shape and not leaking.

Any ideas if this is normal at all? Where should I start in the heater to determine the source of the water causing the steam?

Thanks in advance for your help.


New member
Aug 19, 2016
Gilroy, Ca
Sorry about that. The heater is a Hayward H400FDN. The spa water temp when I started the heater was probably about 48 degrees. Outside air temp was probably around 40 degrees.

I tried adding pool details in my signature line. Hopefly that shows up.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If you do not show any leaks with the pump pushing water through the heater I suspect it is just water vapor. I bet your outside temperature is close to your dewpoint and you can see water vapor due to the hot gasses leaving the vent.
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