Hayward Heater Help


Active member
Sep 21, 2007
middle tennessee
Have a Above ground pool that I installed a Hayward 1001 natural gas heater on..has worked fine..
well it started making a strange sound like,,,popcorn popping when running????Took off the top
cover while running and it's not in fan,,it seems to be comming from inside the big metal
sleeve that the input water goes in and then exits the other side ??..works fine,,just makes
that popping,,ratteling sound in that tube,,any ideas?
Sep 22, 2007
Im by no means an expert in these things-- but recently found out a problem with my Pentair heater--

Mine has a water flow valve in the I/O manafold. Its a spring operated disc that regulates the cold water flow. APparently it keeps the "correct" water pressure/flow through the heater coil-- too fast and the water doesnt heat well. Too slow and it over heats.

I kept hearing this rattling sound when the pump went off. It was coming from the I/O manifold on the heater.

See my post about my heater for more details abou the heating problem-- but..... you might check to see if your unit has such a device.

ADDITION-- The flow valve I removed was toast !! The springs were gone, the frame almost gone. THe previous owners had an inline chloinator installed just past the heater output. When the pump was off, high level CL water would seep back into the heater *shaking head at the builder*
pooldog, It may be the water boiling too if you don't have enough water flowing through the heater. Usually the pressure switch will catch it, but if you're having pressure switch issues, it will not shut down to protect it.
As mentioned, it may be the internal bypass valve is corroded or stuck opened. While you have the system down, there should be a flange on the end of the in/out headers that will allow you to remove the spring and shaft that holds the bypass valve.

Hope this helps.
May 29, 2011
This answer is for a H400 propane heater, but it may apply to you as well...

The banging, creaking, pinging, and shaking is caused by insufficient flow through the heat exchanger, and the water is flashing to steam. It is not safe to operate the heater when this is happening.

The reduced flow can be caused by the following conditions:

- dirty filter/pump basket (you would not have sufficient flow in more than just the heat exchanger if this is your problem)

- bypass valve in front header stuck open (most likely)

- thermostatic control valve in front header stuck closed (can remove it to test)

- obstruction in piping/heater such as pool vinyl, rock, frog, etc. An obstruction in the heater can be observed by removing the rear header and turning on your pump (heater off). Flow should come out of all tubes after a few seconds).

- eroded rear header internals (my problem this time). There is a divider plate molded as part of the rear header that wears away over time (10 years for me). If eroded enough, it will allow flow to travel from one side of the rear header to the other, bypassing heat exchanger tubing.

- worn pump impeller (you would not have sufficient flow in more than just the heat exchanger if this is your problem)

Jim Hoerner