Closed stem leaks while other is open

[Sproksch]

I just replaced both hot and cold American Standard 9C-23 stems and seats in my bathtub faucet with new ones made by Danco. Thought this would be a real quick fix. Everything seems to fit correctly, however the hot water stem will leak if it is closed while the cold water is on. The stem leak goes away if both hot and cold are on and if both are off. The spout does not drip if both are off.

Any advice on how to diagnose this problem? With both stems and seats brand new, it must be either a simple fix or a bad stem. I’m not even sure how it is possible that a closed stem could leak while the other is on and then go away once both are on.

Thanks much for any help!
Steve

 

[hj]

That will ALWAYS happen when the hot packing nut is loose. Tighten it and the problem will disappear.

 

[Sponsor]

 

[Sproksch]

Thanks! I think that was it, although in my excitement I cranked it down so much that I deformed the bonnet around the stem hole. So, now I think I'll definitely need a new stem to stop the leak. Either way, I'll know better for next time - thanks again!

Steve

 

[hj]

Or at least a new packing nut. Leave the "escutcheon nipple" in the next time you tighten it.

 

[Sproksch]

roger that - thanks!

Steve