T&T: Fw: Hot Water Tank plumbing

[Larry N. Brown]

> I am in the process of changing my hot water tank.  The old tank had a
> check valve installed but I can see no reason for it since the Shurflo
> pump has a check valve built in.  Is there something I am missing here?
>
> John Buckwalter
> 42 Jefferson

While I don't hold myself to be an expert on marine plumbing systems, I have 
over 3 years experience with Shurflo pumps on Cigano. In the first place, 
take down the model and serial number to the pump as well as the purchase 
date. They have more than an iron clad warranty. They replaced a pump that 
died 2 years into the warranty on my word alone. I had given the pump motor 
to a friend to power his autopilot and they still replaced it.

You must put a check valve between the cold water supply and the hot water 
tank else the pump diaphragm becomes the de facto expansion tank. When the 
water flow demand stops, the pump shuts down. As the water heats in the 
tank, it raises the entire system pressure above the 60 psi cutoff and the 
pump diaphragm is exposed to over pressure It will fail soon.

My system is plumbed in PEX and this seems to allow for the small expansion 
needed in the hot water side of the system.

If you have any further questions, please ask them offline.

Regards,

Larry and Teri
M/V Cigano, 47' Prairie Sundeck Cruiser
Lying: 64 Cypress Road
          Covington, LA