Leaking Radiator Valves

Mikey_4

I recenty puchased this home and  I am in the process of converting the existing gravity hot water system with cast iron radiators to forced hot water with a TT tube boiler . The system was professionaly drained when I bought it so i never did see it in operation.  I have isolated and  pressurized each of the cast iron radiators, some to 25 psi air,  and they hold for longer than I expected, but graduallly lose  air pressure over night all the way down to zero. I believe all the pressure  to be lost thru the valve stem/packing, as i can hear a hissing sound. I did unscrew the packing nuts, remove the old packing  from around the stem and up under the nut and repack with a graphite packing rope. When I  filled the rads with water to pressure test and flush them, water weeps out of the valve stems. My question is, will this water leakage stop once I run hot water thru them? . What else can I do to ensure a leak tight seal?



 

Brad White

Typically, yes

The packing absorbs water and expands in addition to the packing nut taking another quarter turn if necessary, if you see a bead form.



This is not to say that you are free of other leaks (hope not), but the valve packing depends on being wet to work.



You may also put a dab of Permatex silicone gasket sealant  inside the top of the nut to form a top seal, assuming you will not actually close the valve. The valve should be fully open or fully closed, not in-between.

icesailor

Leaking Valve Stems:

FWIW,

I've been repairing leaking valve stems for more years than I care to remember. All work to some degree and are worth trying. Here's what I do mostly.

I don't see them that often so I usually can't find my 30+ YO spool of graphite packing so I had to improvise. I tale a roll of Teflon tape and pull off a piece about as long as I think I will need. I hold one end and spin it into a rope like thing. The stems may or may not be rising stems. If they are rising, I open the valve all the way. I carefully back off the packing nut and raise it up as far as it will go. I take a piece of sand cloth and fold it so I can get it around the stem. I clean it down to the brass. I try to get all the crud off the stem. I then grease and pack the opening with grease. I find that Super Lube synthetic grease like their Winch Grease is best. It is food grade and used in packing plants to grease rollers on machinery that food could come in contact with. I can always find it in Marine Stores. Many hardware stores. It's really handy because it won't swell Butyl Nitrate O-Rings. I then wind some amount of Teflon rope around the stem. I'm careful not to put in so much that I have a problem engaging the threads. I run the nut down to pack the stem. I run the nut back and put in more with a touch of grease each time. When I get enough packing to feel enough packing in, I tighten it not too tight. I can always tighten more.

If you are really serious about this, pressurize your whole system with air which you may be doing. Get a bottle of gas leak detector and dab it around the finished packing's. If it doesn't make a bubble, you have stopped the leak. It's important to get the crud of dried up debris off the stem. That's stuff left after the water boils away. The better you handle the project, the better the outcome.

If you are switching to a pumped system, I would also look at zoning up the system., I find that the way these were piped make it easy to zone up. They usually have at least two supply and return circuits. On the supply side, I install zone valves. I find that the piping either splits one side of the house, both floors, of the floors. Either way, it is worth splitting it so you have two circuits controlled by thermostats. The old dead guys I knew used to say that you couldn't push the heat against the cold. So they always worked to put radiation on the North walls. If your house is divided so that there is a North side circuit and another South side circuit, it is perfect for splitting. The north side will do the majority of the heating because that is where the most heat is lost. When the heat is pushed to the south, the south will overheat. In a sense, you cut the output in half.

Good Luck