No water from shower

I have a Kohler single handle shower faucet (K-T14422-3BN). Recently, I shut off the main water valve to the house to troubleshoot an unrelated matter. After turning the main water valve back on, I was getting no water at all from the shower. Every other faucet in the house is operating normally but I'm getting no water, hot or cold, to the shower. Thought it might be the mixer cap (GP77759) so I replaced it. No change. I now have a new Pressure Balancing Unit (PBU) repair kit (GP500520) on order but don't expect it for another week. Any other ideas on what might be the problem?

I flushed the faucet valve before installing the new mixer cap and the water pressure seemed to be fine. I'm going to flush it again tonight just to be sure. If I understand how the PBU works, a blockage in the hot water line would still allow cold water to flow normally. I assume if there was a blockage in the cold water line, the hot water would also shut down for safety reasons. So I'm thinking that if the PBU isn't the problem then perhaps I have a blockage in the cold water line??????

I also disconnected the shower head and tried to run the water without the shower head. Still nothing.

One other thing, I've also noticed that when I try to turn on the water, I can momentarily hear the water pressure build up and then just stop.

Any advice would be appreciated. Thx.

Two possibilities I can think of (and there are probably more): the PB valve is jammed to one end - that can shut off both hot and cold, depending on the design; there's some crud blocking the inlets. Sometimes, they use a filter screen, sometimes there may be a check-valve.

On some designs, (no idea on yours), if you take the PB spool valve apart, you can clean it up. Sometimes, just by whacking it against something, you can dislodge it from where it is stuck.

If you can take the cartridge out, then have someone turn the water back on momentarily, do you get water from both the hot and cold ports? Careful, it will spray all over, but you only would need it on for a moment to tell.

I did whack the pbu to no avail in case it was stuck but i'm unable to take it apart. If it is the pbu, the new part should fix it when it arrives next week. Your suggestion to turn the water back on momentarily is a good one. I was going to do that tonight for exactly that reason - to reconfirm that water is coming through both ports. Will post findings....thx.

The PBU will NOT let ANY water flow if either supply line is obstructed or turned off. The PBU is riveted together so you cannot "take it apart". Sometimes you can tap it on the floor then shake it to see if you hear/feel the piston moving back and forth.

If I shake the PBU should it be obvious that the piston is moving back and forth? If so, the problem must be the PBU as I could hear/feel nothing when I shook it...

Yes, you'd feel and/or hear something as you shook it. Sounds like it is stuck. Now, if you have it out and rap it against something, you might free it up, but you may not, and a new one should fix the problem. The typical installation has a sliding spool in it. When the water pressure is equal, it is centered. WHen the water pressure on one side or the other drops, it gets pushed to that end, and that either reduces, or if it is a big enough difference, stops the flow. An example is with a minimal installation, if someone flushed the toilet, using the cold water, you may not have enough volume (and therefore pressure) to maintain your set temperature in the shower...that momentary drop in cold water pressure would also lower the volume of hot water to try to keep things in balance. IF it dropped too far, it would shut both the hot and cold off.

When you have had the main water supply turned off, it may not refill both the hot and cold lines at exactly the same time, and that can cause a big pressure difference, forcing the valve into a position where, when it gets older and stiffer seals, stuck in that position.

Well I finally received the new PBU....flushed out the line real good (pressure from both ports seem fine) and installed the new part. Nothing! Very frustrating. Not sure where to go from here...could the shower arm be clogged? Maybe the water line between the valve and the shower arm? Anyone have any ideas/suggestions? thx.

In that case, you probably have the situation I have had to cure for other plumbers. Debris has accumlated in the well where the tub spout would have connected but is capped off and the channel down to it.. The only way to cure it is to remove the cap, which can be very difficult depending on whether it is screwed on or soldered, (or, as in one I had to do the screwed cap was soldered on which is a completely different difficulty). Then shove a wire up from there to the opening in the back of the valve assembly.

i was thinking of removing the shower arm and pouring in CLR into the line...what do you think? Do you think that might work?