Steel or brass Manifold for UFH?

17 Aug 2010
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United Kingdom
I'm charged with fitting some UFH in a new passageway for my son. This is wet heating with pex-al-pex 16/2 pipe. Pipe laying in screed is all sorted. My issue at the moment is whether to go for a stainless steel or a brass manifold. It will be connected to a heat pump via copper pipe. (Details all agreed with heat pump installer.) I had planned to get a stainless steel one, but started to wonder about the different potentials as the two different metals would get connected together. Does anyone have any input on this? It's just that the steel one seemed to be made in this country but the brass ones are all Italian.
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The usual method is to mount the manifold, lay the underfloor heating pipe and connect to the manifold. Flush and fill the loops and leave on test while the floor is screeded.
If you've laid the pipe, just buy a manifold from an UFH retailer and hope your pipework is OK.
We've fitted hundreds of UFH systems and I've never found myself wondering what the best material for a manifold is.
Maybe you're overthinking this one.
Thanks for the reply. I was unclear when i wrote about the pipe in screed; I just meant it was all planned, with expansion gaps and screed plates etc. The pipes will be pressurised during screed laying. In the past I have always pressurised the pipes during screeding without connecting to the manifold, Probably not so time-efficient I suppose. If the wall for the manifold gets built in time, I'll do it with the manifold!

So I was just concerned, having seem comments in recent threads relating to pinholes developing in heating systems with mixed stainless steel and copper, and wanted to see if anyone considered this a long term problem. As you say, I'm probably worrying unnecessarily.
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If no wall, mount on a piece of ply and make all the connections. Saves pulling stuff apart too many times.
We've had a few issues with early pipe degrading and leaking, air vents weep, flow meters that need replacing but I've never seen a pin holed manifold.
But, can't say I never will.

Good luck with your installation.

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