Question about Hayward H400idl2 400,000 Btu Low Nox Heater Natural Gas

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I have water leaking behind the Thermal Control Value. What can I do? On a hayward H400IDL2 Heater.

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  • brianbruce3 Jul 13, 2009

    Will silicone stand up to the heat? When I turn off the pump I hear air escapeing. It may be in the copper I really can see where the water is coming from.



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Make a hole and silicone in a drain hose, or silicone the leak directly

Posted on Jul 13, 2009


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I have Hayward H400IDL2 heater I recently had #1 and #2 1.5 amp fuses blow. I replaced them and then the #4 2.5 amp blew so I replaced it. When I press the mode button to spa the heater blower comes

Good Day, missed your post for a few days. #1 & #2 fuses are on the high voltage side. This could mean a problem with incoming voltage or a bad fuse or main circuit board. Call our tech line at 908 355-7996. I have attached a link to the manual.

Aug 24, 2014 | Hayward H400idl2 400,000 Btu Low Nox...

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lack of water flow check inside bypass

Apr 12, 2014 | Hayward H400idl2 400,000 Btu Low Nox...

1 Answer

Why does neither UP nor DOWN adjust my temp?

Typically this means the heater is in remote mode and is controlled by an outside source ie, control panel or automation prodict

Dec 01, 2011 | Hayward H400idl2 400,000 Btu Low Nox...

1 Answer

Hayward H400IDL2 pool heater with service code SF

call manufacturer then get tech support they will walk you through it and help you

Nov 27, 2011 | Hayward Pool & Spa

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Five year old Hayward H400IdL2 makes a banging noise when the heater is turned on. Pool man mentioned a bypass valve problem. Leslie's pool said we need a new heater, at a cost of $2,300 (including labor.)

Thank you for posting your question here on

Does the banging continue until the heater eventually shuts off or does it quit shortly after the heater burners start up? In either case you can repair the heater for much, much less than a new unit. The bypass may be the issue if it is stuck closed. You will also want to inspect the control valve in the header and inspect the overall condition of the heat exchanger. It is likely aggressive water has damaged some or all of these parts causing the banging noise you hear. It is also possible there is an issue with the pump and/or filter not getting enough flow thru the heater but I have to assume your pool man eliminated those possibilities when he looked at the heater.

Was the pool man not able to repair or at least inspect the heater further for you?

If this answer does not fix your problem, please comment with additional details prior to rating the answer. Positive feedback is appreciated once your problem is solved!


Dec 07, 2010 | Hayward H400idl2 400,000 Btu Low Nox...

1 Answer

Hayward H400iDL2 pool heater burned up after only 3 seasons!

I dont know about your particular model. I do manage two Hayward 380,000 pool heaters that are natural gas fired and I have never had this problem you describe.

I also manage another dozen or so assorted other gas and propane devides. One propane device sooted so bad we had to discard it. It did this, according to the propane tech, because it couldn't breathe - there were louver type vents on the door that leads directly outside. He did, however, find a ruptured diaphram in the regulator and he replaced it. Hmmmmmm, couldn't breathe eh????

I'm not too surprised at the repair cost you cite. The exchanger is of course copper and there is the labor involved and lots of it. The age of your unit at this point is not relavent. What you do need to determine is why the unit sooted up like this. If you are gas fired, you know this is considered a clean fuel (compared to all others except electricity). What ever caused it must be repaired or you will be looking at another sooted up problem and repair ... and it will not be in three years, it could be next week.

I hope you find some value to my comments . Thanks for posting this question at

Positive comments welcome


Nov 02, 2009 | Hayward H400idl2 400,000 Btu Low Nox...

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