Question about Hayward H Series Pool & Spa Heater 400k Btu Propane Gas Milivolt Ignition H400p1

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Hayward H series pool heater diverter plate moves

I rec'd info from John 224 about my Hayward H series 100,000 btu AG heater regarding the diverter plate being broken and causing the water to boil. Is the plate to be welded supposed to be welded in the down or up position on the inlet side ? Same question for the outlet side ? Any ideas ?

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Next to the water inlet oulet is got to be either two bolts or a silngle big plastic nut all depens on the model take off when system is off!!!and replace if needed

Posted on Sep 14, 2009


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Hayward h250

Hi this is John the Hayward tech. If you have a millivolt heater it will only have one therm and an on and off switch. What you are describing is a electronic heater. Please call our tech line at 908-355-7995

Aug 28, 2014 | Hayward H Series Millivolt 250,000 Btu...

1 Answer


yes, that is one of the many great features of these heaters.

Jun 16, 2014 | Hayward 100,000 Btu Heater For Ag Pool And...

1 Answer


is this heater is been install for above the ground pool it will be better either way to use a hard schedulle 40 pvc to prevent any checking in the hoses for future leak ,is the heater connections are correct in and out , mean from the return the filter go to inlet side the heater them the outlet side of the heter (HOT WATER) GO TO RETURNS of the pool ? also check if the pump got full prime not air,is the filter is clean? also check for any brocken parts inside the flowvalve control, after years low PH AND TA will destroy internal parts in heater include leaking heater exchangers.

Jun 09, 2013 | Hayward 100,000 BTU Pool Heater H100ID1 -...

3 Answers

I have a hayward H100ID above ground pool heater. Recently the heater is making a rattling sound and the in and out hoses are bucking or pulsating. The water is still being heated but somehting does not...

Thank you for posting your question here on

The Hayward H100 has a diverter plate welded into the header that helps direct some of the water flowing thru into the heat exchanger to heat the water. If the weld fails the diverter can interfere with that flow and cause overheating or poor flow thru the heater which in turn can lead to the problems you describe.

Remove the inlet side hose once you have blocked the flow of water from the pool and you should see the diverter in the inlet. If you can move it then it is broken and needs to be fixed back in place or the whole heat exchanger needs to be replaced.

If the diverter is not moving then your issue is likely an overall water flow one and the next place to look is the filter. Poor overall system flow may be enough to close the pressure switch telling the heater the pump is on but not enough to keep the water in the exchanger from getting too hot, again causing the symptoms you describe.

If this answer does not fix your problem, please comment with additional details prior to rating the answer. You may also contact me thru our website at Positive feedback is appreciated once your problem is solved!


Aug 30, 2011 | Hayward 100,000 BTU Pool Heater H100ID1 -...

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My hayward fires up for about 6 minutes then shuts off with a LO alert blinking

You problems could be in any of the following areas per the Hayward owner's manual. If you need help with continuing the diagnosis please comment with what specific help you need.

john224.jpg If you can not enlarge this enough to read it, please contact me thru our site at and I'll email the manual to you. If you have the manual that came with the heater, your troubleshooting info is on page 38.


Nov 08, 2010 | Hayward H Series Pool & Spa Heater 400k...

3 Answers

Hayward 100 series Above Ground 100,000 BTU heater

This plate is an internal by-pass if it sticks open this is what you will get if it sticks closed the water will move to fast to heat and you will get low heat after it runs way to long. If it moves freely and has the proper spring in it you will get nether of these. For my money i would replace it with a new one and be careful with your chems as this is what will kill on and after time ruin the whole heater. Figure they pay a bunch of engeneers to get it right and virturaly all heaters have these in them in one form or another. In answer to your question you will want it stuck closed, but be reminded your heater will run on about twice the gas and get you mabey two thirds the heat.

Sep 03, 2009 | Hayward 100,000 BTU Pool Heater H100ID1 -...

1 Answer

My Hayward AG 100,000 btu heater ran well for the last two seasons. This season I hear a rattling type noise, and the hose that feeds the heater shakes at times. Other times the noise and shaking subside....

That plate should not move at all. If it is moving is is damaged. In the past that meant replacing the heat exchanger but I recently had someone tell me they took theirs to a radiator shop that tach welded the plate in place and it works fine now. Either way, the rattle is from water boiling in the unit due to poor flow through the heat excahnger. The plate we are talking about is what controls that flow.

Jul 06, 2009 | Hayward H Series Induced Draft Abg 100,000...

1 Answer

Hayward H300 heater runs but will not heat water

Your internal by-pass could be stuck open or the disc could be worn to the point of letting water pass too fast. Or your thermal control valve could be stuck open. These are both found in your water header going into the heater. Hope this helps, good luck.

Jul 02, 2009 | Hayward 100,000 Btu Heater For Ag Pool And...

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