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Radiator Flow Valve Replacement

I am replacing the 'frozen' control valve on one of several radiators on a hydronic system. I have the radiator away from the wall, replacment valve, and spud wrench in hand. (Painted the radiator itself and wall behind) Before I re-assemble, is there any advantage to removing the black, oily, slighly smelly liquid in the bottom of the radiator? Is that oil there for a reason?

Re: Radiator Flow Valve Replacement

It's iron oxide, although it looks like used motor oil.

Iron oxide forms naturally over time when hot water courses through steel pipes and cast iron radiators.

It's most likely to settle in the lower sections of cast iron radiators.

It's harmless, but yes, it should be removed to help keep the boiler water relatively clean; sometimes there are bits of metal from a broken valve, etc., that can damage the boiler pump's impeller.

Lay a plastic drop cloth on the floor, then a flat pan on one end & (if it's a large, heavy rad) use a crowbar or an 8 foot 2 X 4 as a fulcrum lever lift on one end to get the black goo out.

Avoid getting any on a carpet, because it tough to get out; you should bleed the radiator vents at the highest spots to get out any accumulated air.

Some people attach a rectangular piece of reflective insulation sheet or a piece of aluminum/steel (Home Depot/Lowe's) the diameter & height of the radiator to reflect the heat away from the wall (where it is wasted) & into the room.

Re: Radiator Flow Valve Replacement

NashuaTech: Thank you for your response. It was very helpful. Any advice on getting the unions to stop dripping(other than plumbers putty or thread tape)? I suppose you cant over tighten the joints.

Also, I apparently stripped the threads on either the radiator nipple or my new valve in one occasion. I have an extra valve, but reomving the nipple in the radiator is the hard part. If I remove the loose collar with a hacksaw, and then make a transverse thru the nipple, just up to the radiator, and use a cold chisel to collapse the nipple and remove. Is there a better way? I assume I will not get a grip on the nipple with the monkey wrench, nor do I have a vice-grips big enough to get around it. Please confirm or suggest another method.


Re: Radiator Flow Valve Replacement

The proper tool to remove a frozen nipple (called a spud) is to use a spud wrench.

The nipple (spud) is first well oiled with penetrating oil (preferably overnite).

The spud tool that has several gradations of size from 1/2" to 2" & is slipped into the nipple (spud) & pounded with a hammer to get a firm grip on the inner part of the nipple, allowing the use of a pipe wrench on the spud wrench to turn the frozen nipple out of the rad.

Google "using a radiator spud wrench"

The tool can be obtained at heating supply houses for approx. $15; some Ace Hardware stores carry it, but I've neve seen it in HD/Lowe's.

The danger if the SW is hammered in too hard is the nipple will break off flush with the rad body & may not loosen.

In such a case some people use a sawzall reciprocating saw with a fine metal-cutting blade to CAREFULLY cut a crease in the remaining nipple in several places AVOIDING DAMAGE TO THE THREADS OF THE RAD, and using a cold chisel to remove the offending nipple.

Rectorseal pipe thread sealant ((approx. $10 for 1/2 pint can) is then used to seal the new nipple (spud) as well as to connect to the new valve.

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