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Thread: Hayward H400 - banging noise

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    Hayward H400 - banging noise

    I found several posts on this topic most indicating the plastic barrier is broken in the bypass valve such as:

    I have the old style (pre-04) brass, etc... My plastic piece is intact, but there was corrosion on the brass such that it wouldn't move up and down the shaft. I cleaned that up and it slides now. Put it back together, same noise. Pulled it apart again this time pulled the manifold - noticed the thermostat surround was severely corrosed and cracked on the rod above the spring. Would seem off for this to make that much of a noice, but just to see, i removed it, reassembled and fired it up and no noise.

    Last thing - i have upgraded to a variable speed pump and the rpms and pressure are definately down from the 2.5HP pump i had before that used to pump up two stories of solar (no longer installed). But without the thermostat it was fine, so i suspect flow isn't my issue. On low speed the unit shuts off as i'd expect with LO indicator. Anyway doubt this is the cause , but throwing it out there.

    Main question , could the thermostat truly make that much of a ruckus (i guess if it's stuck, the answer is yes?

    Since i've got this apart, i probably need to ream out the burners. Should i clean the water tubes with a muriatic acid solution while at it? Any tips on either (i don't have a reaming tool yet - if something else would work)? Also, even though the unit is on a pad, the bottom steel case around the burners is starting to flake/rust. Assuming that's normal where rain water would pool up?

    thx in advance

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Hayward H400 - banging noise

    The stuck t-stat can certainly make a lot of noise. Anything obstructing the flow path can create turbulence and make a heck of a noise.

    Don't use acid to clean the exchanger. You can get a burner cleaning brush and brush the burner tubes out.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    ps0303's Avatar
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    Jul 2011

    Re: Hayward H400 - banging noise

    If you are considering reaming out the heat exchanger, I would second think that. If any part of the copper tubes is think you risk the chance of putting a hole in them. You can use a wire brush to clean the tops of the burners but again, you risk the chance that the burners are not 100%.
    Paul A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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