Repairing a leaky valve stem

Question

I'm replacing the valve stems for my 1960's bathtub handles. There's a hot and cold handle, and they both are leaking profusely from the stem (not drips, but streams of water).

This picture generally agrees with what I've seen so far - previously I tried to replace the entire valve stem, but I don't think it's made anymore. The closest I've found is a Danco 10B-9H/C (https://www.danco.com/product/10b-9hc-hotcold-stem-for-gerber-faucets/), but the stem has too many threads to fit my fixture.

I replaced the seat washer, and re-greased it and the bonnet washer (could not find a replacement for the bonnet washer). This fixed the original problem, which was regular dripping from the faucet itself. Now the handles are spewing water when they are turned on. From inspection, it looks to be leaking out of the inside of the packing nut. Based on the picture above, I think it is because I destroyed what little remained of the original packing washer (I soaked the valves in alcohol and cleaned them internally and externally with steel wool). This means that the water is sneaking by the stem threads and leaking out of the front of the packing nut (facing into the bathtub).

Knowing this, I think I have a few solutions. One, I could use graphite packing string on the stem threads. Two, I could use teflon tape on the stem threads. Or three, I could use plumber's grease on the stem threads.

Which of these choices is appropriate? Stem threads regularly move (anytime you turn the handle), so I'm not sure any of the above methods could handle that regular motion. I can't find any information telling me if they can. However, I can't locate a new packing washer or stem.

How should I repair this leak?

Answer 1

I think I have a few solutions. One, I could use graphite packing string on the stem threads. Two, I could use teflon tape on the stem threads. Or three, I could use plumber's grease on the stem threads.

None of those proposed solutions will work because the problem has nothing to do with the "stem threads". Your problem lies with the missing packing. The valve design incorporates what is called a packing gland, which includes a packing nut, a stuffing box, and packing material.

The stuffing box is where packing material (in your case probably a washer) is supposed to be. The packing nut screws down onto the packing, causing it to squeeze around the stem, which prevents the water from passing through.

You should take the valve stem to a good plumbing shop, where they will have a wide selection of various size packing washers to choose from. If none are exactly the right size, it is very common to trim down a larger packing washer with a knife, to make it fit. It is also very common to use packing string (you mentioned it in your post) in lieu of, or in combination with, a packing washer.

This pic illustrates the theory but instead of a packing yoke with bolts, your valve uses a packing nut: