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poolguy810, owner - pool and spa service company
Category: Pool and Spa
Satisfied Customers: 1675
Experience:  Servicing pools and all brands of spas for over 28 years.
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Have a loud knocking noise wit a series H200 pool heater.

Customer Question

Have a loud knocking noise wit a series H200 pool heater. What would cause that?
JA: Who manufactured the pool?
Customer: Hayward
JA: Do you plan on doing the work yourself?
Customer: yes.....I know the unit pretty well now. 3 seasons old
JA: Anything else we should know to help you best?
Customer: It seems to run very HOT now. I cleaned all the fins on heat exchanger and checked all gas tubes. All is clear now but still runs hot and with knocking.
Submitted: 1 year ago.
Category: Pool and Spa
Expert:  Webb-Guy replied 1 year ago.

Hello and welcome to just answer my name is ***** ***** I will be the one who will try to assist you today.

If you have an external by-pass it needs to be closed. This will be a valve between the pipes in and out of the heater. When you close it, it forces water through the heater. When it is open no water goes through the heater. So the water in the heater boils and turns to steam. With no where to go it starts banging and jumping.
If you close this valve or it is closed and you still have trouble the internal by-pass has gone bad. The overheating from the first problem will often cause this.
You remove the water header from the side of the heater and pull the pipes from it. In reality you will probably have to pull the gas pipe so you can move the heater from the pipes. You will find the assembly inside the manifold. It will probably come out in pieces but the new one goes back in as a unit.
This will regulate your water flow and keep it heating at a constant temp.