We have two separate shower units in our shower. I have been reading MANY posts about no hot water in the shower. We have replaced the cartridge several times. We have taken the complete cartridge out and let water flow through the pipes. Only water comes out of the cold side. When we cover the cold side up there is NOTHING coming from the hot. We have a moen posi-temp that is about 20 yrs. old. It has the one handle. There are no shut off's on the pipes inside the walls. We put a tiny camera that fits on a wire down the opening to look. We have been able to get a rotor rooter down the pipe and even past the first turn. There seems to be no blockage as far as we can tell. The shower on the other side works just fine as well as ALL the other plumbing in the house. They ALL have hot water except for the one shower. It worked just fine when the house was built 20 yrs ago. After about 3 or 4 years, it just stopped working. It has been like this for MANY years! We have just used the shower head on the other side with separate components. We are getting ready to do a complete makeover of this bathroom and would really like to have BOTH shower components working, especially if we have to open up some walls or ceilings before completing the makeover. It is on the second floor of our house and the water heater, which works just fine, is in the basement. We can NOT get to any of the pipes without cutting the drywall. Does anyone have ANY suggestions to figuring out WHERE the problem is or WHAT the problem is???? As I stated before, there are no cut off valves for the shower. There is one where the hot water tank is for the whole house. I don't want to call a plumber out and have him start cutting out drywall and pipes not knowing WHERE the problem is. I have looked online and not found this exact problem. Could use ANY ideas or help???? Thanks in advance!

You say you have two shower units, do you mean shower valves? Try to read your message and see if you are saying exactly what you mean. When you put the tiny camera down inside, was that inside the wall or the pipe. I am thinking wall but be specific. From what I gather it seems you have a stoppage of some type in your hot water line. Have you tried to drain your water heater to see if mineral deposits are blocking the drain valve? You might get an air tank and pressurize hot line only by closing the valve at the water heater, then disconnect a flex connector at a lavatory or other hot fixture that is working properly, to connect an air valve so you can blow out whatever it is. Being a hot line it could be mineral deposits from the water heater that has lodged in the copper somewhere. I assume it is a copper line but could be another type of piping. We want to help but need solid facts to deal with in order to detect your problem. Good luck.

In the shower that won't emit any hot water: remove the shower head and install a 1/2" cap over the shower arm. Turn the shower to warm. In the second faucet, turn the water to straight hot.

If there is something blocking the flow, the first valve should create a cross connection that will cause some back pressure on the hot water line; the second shower will be attempting to take all the hot and thus create a pressure differential that may dislodge something if it is stuck. Let this go for 20 seconds and shut off both valves. Turn off your water and take the cartridge out of the first faucet and see if anything will flush out of the hot side if someone turns the water back on.

Sorry! I thought I was being exact. The pipes are copper. We put the tiny camera inside of the walls to see if there was a shutoff valve or anything else of significance. There is nothing there except for the copper pipes. We have checked and drained the water heater tank. It works fine. We have tried to flush the pipes by turning the hot water only on and leaving the cartridge out and running the water for several minutes. We have done this several times now. It didn't seem to do any good. We are thinking it is something stuck in the pipes, but we don't know where (or if that's it) it is stuck and don't want to start cutting into walls and ceilings to try and find where and what it is. We have one shower with two completely separate shower systems. Both the piping is separate as well as two separate shower heads, and two separate single controls for the heat setting. Each unit is individually controlled. We have shower heads and controllers on each side of shower (right and left). That's how we have been able to still use the other (right side) shower in the same unit to keep clean. It was originally SUPPOSED to be a "his & hers" shower. They are NOT dependent of one another. I hope I am explaining this so you can understand it?? Currently the shower head as well as the cartridge are out. Nothing at all comes out of the hot water side. Plenty of water comes out of the cold side. We know this because we managed to block the cold water coming out and there was no water at all coming from the hot side where they SHOULD mix. Every single faucet (incl. the two in that bathroom), shower, etc. works in the WHOLE house. Even the other shower on the opposite side works fine. My husband has gotten a rotor rooter thing to go inside the pipes past the first bend all the way to the floor where there is another bend. He can't get it to go past the bend in the floor because the rotor thing won't bend that far down. There is no blockage at least that far. So frustrating as I said before because we do NOT want to have to tear into the drywall to try and find the blockage, if in fact that's what it is. I don't want to call a professional as we don't know what more he could do than what we have already tried. We live past city limits and don't have "neighbors" close enough to tap into their system to do a check. Please HELP! We are having our bathroom remodel next week and it sure would be nice to have two shower systems in working order rather than just the one. Especially if we end up purchasing new shower systems (shower heads and handles) to update the old ones as well as the faucets on the sink so they all match. Thanks again for ANY advice!

Read above again.

KCRotor,
We did try your suggestion and still NOTHING!!! We went out and bought a shower arm cap as well as a moen cartridge plug to plug up the unit so we could try and dislodge something. We tried it both with the moen plug in as well as out and nothing changed. We tried MANY times and ways and still no change. I guess we are going to have to start cutting into the drywall. We don't know what else to do??? Don't know what more a professional could do other than what we have already tried? SOO frustrating!!! We can't even tell where the pipes go before or after the shower? The camera inside the wall followed the copper pipes all the way to the floor, but then after that, it got too dark inbetween the walls to see where the pipes went. We are still willing to try and suggestions you may know of? Thanks for TRYING to help us!
Silene

Adapt a Schrader valve to the showerhead and shut off the main water, drain the water heater and keep the drain valve open, keep the cold inlet to the water heater off, turn the shower valve to hot and blow compressed air through the showerhead. You need to blow back any blockages.

the fact that it is a Moen means that you won't be able to put anything through it without pressure coming through both the hot and cold lines, it is really a pain to deal with in a situation like this. If one shower and everything else is working, the problem has to be in the supply line between the affected shower and the supply branch that feeds it. if you can get to it through a wall from the back side instead of the tile it is much easier to repair and work on. Best of luck.

It may be easier to adapt a male air hose connector with a coupling and connect it that way instead of a schrader valve