My shower riser appears to be almost completely blocked - probably by scale. Almost no flow, even with shower head removed. Have removed the Kohler valve and cleaned completely, no luck. Also removed valve guts and just replaced the valve cap; still no change in flow.
The valve is shower-only, no tub. But strangely, the outlet to the riser appears to be down and there is no upward-facing outlet. Have cleaned the valve body and visible areas of the outlet. Have not tried to use air pressure backflow on the line yet to test, but I assume that will confirm the down-facing outlet.

Need help with how to de-scale the riser.
Thanks!

Do you mean the water comes out of the bottom of the faucet, then makes a 180 degree turn and goes up to the shower head?

I would attempt to use high pressure air from the shower arm or the drop ear inside the wall to force any debris back out. It could be a chunk of rubber from a washer wedged in there. If it is hard water buildup, you could use a syringe (like a marinade injector) to shoot some white vinegar down the drop ear at the shower arm and let it sit. If you were to put the cartridge back you could basically fill the riser to the shower head and let it sit for a couple hours, then simply turn the water on afterwards to flush the line and test the flow. I would still try the high pressure air first if you are able.

Yes, that's what I suspect since I can't find an upward-facing outlet. Doesn't make a lot of sense to me that someone would have used a 180 in the wall downstream of the valve, but that's the way it appears from the valve body. It's all behind tile, so not easy to break into.

KCRoto, thanks. Will give the air pressure backflow and the vinegar a try once I can have the water off for a few hours.

How do you KNOW there is no upward opening if it is buried in the wall. IT would make more sense if there were one, because then you would have a Kohler valve with a common problem. I have had several with the same problem, (in fact other plumbers call me to fix them when they find one like that).

HJ - This is a Kohler 'Early' pressure balancing valve. See pics below the description for the 'early' versions in this link from Kohler.
[helptopics.us.kohler.com]

The valve body interior is visible when you remove the cap and the pressure balancer, of course. The inlets coming to the pressure balancer are at the back per typical, but there appears to be only a single, downward-facing, outlet. (I.e. it's not a shower/tub valve with both up- and down-facing and one outlet capped off for this shower-only application). Unfortunately the tile is close enough to the valve body exterior surface that I can't see the pipes leading to or from the valve body. So far I have not been able to feed any kind of a fish wire down that outlet more than an inch or 2 though.



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You are extrapolating the wrong way. That opening DOES go down, but it goes down to the "tub spout" outlet which has a plug in it. From there it goes back up, internally, to the shower opening on top. That plug on the bottom has created a "trap" which has filled with mineral deposits. You have to remove it, then shove a stiff wire UP through the hole and into the shower body through that small hole. Then put it back together.

HJ -
Remove the valve body? As in tear out the tile, unsolder the pipes, etc.?

hj and and KCRoto -
Thank you for the help and ideas on this.

Luckily, I did not have to take anything apart further. I used a hose and a kitchen baster to blow a quantity of white vinegar back thru the shower pipe toward the valve. Left it to sit for about 4 hours, put everything back together, and now there is plenty of flow! There was some black residue at the bottom of the valve body tile ring; couldn't tell if it was from something inside that had been attacked by the vinegar or from the black plastic hose I'd used to insert the vinegar. All of the seals were removed during that process, so it should not have been from any of the seals.

I now have a small drip from that shower head that I didn't have before, so it's off to find replacement seals for that old valve assembly.



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NOPE!! Remove the trim plate, and open the wall at the bottom as far as you can and stay inside the limits of the ring. Hopefully, the plug on the bottom is NOT soldered in, (which most of the ones I have worked on were). Remove it and then you can "ream" the openings from the bottom.

Replace the pressure balancing unit and that should cure the drip.