Is check valve needed on cold water supply leading up to buffer tank and desuperheater?

When hooking up a desuperheater and buffer tank, should the cold water input line leading up to the T that splits off such that one branch goes to the desuperheater in and the other branch goes to the buffer tank cold water in, have a check valve _before_ that T?

I have a GeoStar ground source heat pump in my house, with the desuperheater hooked up including a buffer/preheat tank before the house's main on-demand hot water heater.

The problem is that plumbers who did this (I was not in the house then), apparently didn't know what they were doing, and didn't plumb things correctly.

The correct plumbing of the desuperheater is as per page 10 here ( http://www.geostar-geo.com/literature/IM1585X.pdf ) with the hot water out from the desuperheater coming into the bottom of the buffer tank via the drain valve.

Instead, they brought back the hot water out from the desuperheater, and via a T, connected it to the hot water out from the tank. But there is a check valve on the hot water out line from the tank, so no way the hot water from the desuperheater could ever get into the tank.

When the system is operating a lot now, in the winter, the result is that my entire cold water supply in the house gets heated up. I get hot water out of my cold water taps for a good 10 minutes before things cool down and I start getting cold water.

There is currently no check valve on the cold water line leading up to the buffer tank and desuperheater.

In a few days, I am going to have a plumber move the hot water out from the desuperheater so it properly goes into the buffer tank at the bottom as it should.

My question is if at the same time I should ask him to add a check valve on the cold water supply leading up to the buffer tank and desuperheater (before the T)? I think it is needed, but the plumber is a bit worried that if he puts it in, the cold water system can not act as a buffer for any thermal expansion that may happen.

Any advice?

Thanks,
Colin

 

Change

the piping to do as you describe.

 

Mark,

Thanks for the reply, but do you mean with or without the check valve on the cold water supply?

Colin

 

I do not think you need the check valve

....unless the location of the buffering tank would allow ghost flow caused by thermal differances.