Home>Discussions>PLUMBING>Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.
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Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.

Hi. I have a hot water system with radiant heat baseboard, running of a weils mclean boiler.

I have absolutely no pressure with the cold water from the house turned on to the system. I had a guy out here

who said I should have pressure even without the TACO circulator pump & boiler turned off.

I am sure he is right, but I am just verifying.

The pressure gauge comes out of the side of the boiler.
So does my pressure gauge need power from boiler switch (it has a light switch thingie) turned on? to work?

I just want to make sure before I have american leak detectors come out here.

Oh, and the guy before this guy from craigslist, he removed my backflow preventer and didnt put a new one on.

pictures in next post...

Re: Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.
Re: Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.


The 2nd photo you posted is a lot clearer, but it still doesn't show all the associated components connected to your complaint of no water pressure with the water turned on coming from the house.

Your first step is to give us the present reading on the pressure gauge located on the front of the boiler---the needle of the gauge should be pointing to approx 12-15 psi as the present boiler pressure--are you saying that you don't have any boiler water pressure now, and the gauge needle is pointing to zero?????

Please post back.

Yes, the first repair person you called in is correct when he says that there has to be at least 12 psi water pressure showing on the PSI gauge; but if the boiler is old, it could be that the boiler has the correct water pressure but the gauge needle is defective & has to be replaced; also, one of the supply valves may be internally rusted, but unless you have a pool of water on the floor next to the boiler, I don't see how the boiler would lose its 12 psi charge.

If you HAVE NO boiler water pressure reading you shouldn't be running the boiler until you can get someone in there who can check out & troubleshoot what is wrong with the system---simply turn off the electrical boiler switch (usually at the front of the boiler, or by the stairs) and use electric heaters to keep warm until the service person arrives; try tapping the gauge on the boiler lightly with your knuckle to see of the needle moves up to its usual place.

I've also noticed some other rusted components in the photo you posted, & it's possible that the water supply coming from the house has been blocked due to an inner rusted-out valve.

For background info: the HOUSE water pressure usually varies anywhere from approx 90 psi to 120 psi, depending on your local water dept. pressure, or the pump controlling your well water; there is a pressure reducing valve (PRV) that reduces the local water pressure from 90-120 psi DOWN to 12-15 psi for all the boiler piping & the boiler itself, via the pressure reducing valve, since the heating system does not need high water pressure, the lower 12 psi for all boiler & heating piping prevents catastrophic leaks to ceilings, walls, sheetrock, etc. in the event of component failure.

The diagram below of a typical boiler system shows the piping arrangement of a typical hot water heating boiler/system; notice on the right of the diagram that there is a pressure reducing valve (PRV) that REDUCES the house water pressure down from approx 120 psi to 12 psi---so all the piping, the boiler & other heating system components all operate at the 12 psi stated pressure; the diagram shows on the left side of the diagram an alternate way of connecting the house supply to the boiler supply.

Scroll down the page to L.E.S. Inc. Boiler Room Equipment to view the diagram of the oil-fired hot-water heating boiler; you may have a gas-fired boiler, but the diagram can be used for gas or oil-fired systems.

Aside from the simple steps noted here, I don't think it's a good idea to attempt this repair yourself & recommend you get another service person in there; the back flow preventer valve has to be replaced, as well as any other components that are rusted out & may be ready to fail.


Re: Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.

Excellent reply from Dodsworth :) The backflow preventer will be required by code so that cold piping cannot be filled with scalding hot from the pressure in the boiler should the PRV fail. Whoever removed it is not qualified to be doing plumbing work of any kind.


Re: Weils MClean boiler, hydronic baseboard water heat, slab, backflow preventer.

Thanks, Phil

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