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locknut 04-24-2009 05:38 AM

Leaky tank shutoff valve
One of my fears in servicing a toilet tank is that when I re-open the feed valve, they often will leak (slightly to fairly much) out through the stem. In some instances I observed that they will mysteriously stop leaking after a few days. In other cases, I found that running the stem in a bit will stop the leak. So far I haven't needed to fully repair or replace a valve.

Nestor_Kelebay 04-24-2009 04:34 PM

This is common on a certain kind of valve called an "Emco compression stop".

If you have a digital camera, can you take a picture of the feed valve, register on a site like Photobucket and upload it so that we can see exactly what kind of valve it is?

Redwood 04-25-2009 12:45 AM

probably brasscraft in the us

locknut 04-25-2009 04:50 AM

As yet I haven't invested in a digital camera. If necessary, I suppose, I can remove the stem and replace the washer (assumedly). At this moment the leak has almost stopped and with any luck there will be no more problems. Thanx

majakdragon 04-25-2009 07:04 AM

Sounds like a typical packing gland leak. If you tighten the nut under the handle about 1/4 turn, the leak will usually stop.

Nestor_Kelebay 04-25-2009 10:39 AM

Locknut & Majakdragon:

There are some inexpensive 1/2 inch solder-in water shut off valves that don't have packings or packing nuts. They rely entirely on a rubber O-ring to stop water leakage past the stem.

Rubber materials suffer from something called "compression set", which is where the rubber of a compressed O-ring (like the one between the stem and bonnet) will gradually flow into the shape it's compressed into. That is, you now have an O ring with an elliptical cross section, not a round cross section, even when it's not compressed into that shape.

When people see such flattened out O-rings, they presume the rubber on the ID of the O-ring has worn away, but that's not true since water shut off valves spend 99.9 percent of their time open with no movement of the spindle inside the O-ring. What's happened to cause that flattening out is "compression set"; the rubber has simply flowed into it's compressed shape. And, once that happens, it doesn't exert the outward pressure needed to stop leakage past it.

If this is an Emco compression stop, the fastest easiest fix is to replace the O-ring every 5 to 10 years. And, if it was me, I'd replace the rubber washer and the bibb screw at the same time.

And, if these are Emco compression stops, if you take the handle off, you should find that you can slip a 5/8 inch ID vinyl or rubber hose over the end of the bonnet nut. So, if the valve just won't stop leaking past the stem, slip a piece of 5/8" ID hose onto the bonnet nut, and put a container on the spot where the water drips out of the hose. Eventually, the valve should stop dripping.

The reason why the valve should eventually stop dripping is a matter of physics. For a fluid to leak past an O-ring, the pressure of the fluid has to be greater than the outward pressure exerted by the O-ring. Where the O-ring is compression set and isn't exerting any outward pressure of it's own, then theoretically, the OD of the O-ring is exactly equal to the ID of the bore that it's in. However, because the pressure on the opposite side of the O-ring in this case is atmospheric pressure, that O-ring is now being compressed by the fluid toward it's original shape. So, if the water in the piping is 45 psi, it will squeeze on the O-ring with a pressure of 45 psi, and the rubber of the O-ring will push back on the water with a pressure of 45 psi (otherwise the O-ring would move). However, rubber is not a solid, it's a very viscous liquid (which is why it compression set in the first place). So, if the pressure on the rubber is 45 psi, the pressure inside the rubber is 45 psi, and that pressure will be exerted outward in all directions, including against the bore the O-ring is in. So, the external pressure on the O-ring should result in exactly the same internal pressure inside the rubber, which will eventually cause it to seal against the bore with that same pressure. It all relies on the fact that rubber is a very viscous liquid and can flow in response to an applied force.

Where are those valves located? If they're readily accessible, it would be better to learn to solder and replace them. If they're not readily accessible, then it's a simple matter in a house to replace the washers and O-rings in them every half dozen years or so.

MACPLUMB 04-25-2009 05:45 PM

Angle stops leaking at packing nut
There is two simple ways to fix this ! !
First you need a 8" and 10" crescent wrench's a small piece of mop
string or if you use a sponge mop, you tear off a 4" to 6" piece of teflon tape while holding one end in between finger and thumb
take other hand fingers and start at the end where you are holding the tape spin the tape between your fingers till it forms a string,
turn the water off to your house then holding the valve with the 10" wrench use the 8" wrench to back off the packing nut under the handle, do not remove just enough room to take your string
and wrap it " clockwise" around the stem under the nut then screw the nut back on just a little pressure on wrench if you over tighten it will keep stem from turning ok ! ?
Restore water to house and test turning valve on and off a couple of times if still leaking lightly tighten the nut till leak stops and still turn handle by hand

note; this works on all compression packing nuts even under ball valve handles

35 yr. Masterplumber
with a ph.d. In water heaterolgy

Nestor_Kelebay 04-25-2009 06:17 PM


Does the shut off valve to your toilet tank look anything like this:

If so, then it's a Brasscraft stop, and the easiest fix is to just buy a new Brasscraft stop, shut off the water to the house, remove the bonnet and stem from the old valve and screw on the bonnet and stem from the new valve.

Redwood 04-25-2009 08:02 PM


Originally Posted by Nestor_Kelebay (Post 29911)

Does the shut off valve to your toilet tank look anything like this:

If so, then it's a Brasscraft stop, and the easiest fix is to just buy a new Brasscraft stop, shut off the water to the house, remove the bonnet and stem from the old valve and screw on the bonnet and stem from the new valve.

That is what I would do!

RandyJ 05-02-2009 12:05 PM

I've gone to NEVER using a stop with an o-ring or washer. I now only use 1/4 turn ball valves and never have those problems once I leave the job...not very good for job security but I get a very happy customer.

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