I have been looking everywhere for ideas, but our water pressure in the bathtub and shower has deteriated due to a clog. I took off the handle (it is similar to this one: http://www.youtube.com/watch?v=6MrhmIGNNv4) and I even tried to snake it but since it comes in at 90 degree angles I was unsuccessful. Does anyone have any ideas on how to access these pipe behind the wall without having to rip the wall out? Coming from the shower head won't work because it just joins in the middle so you would end up with the same 90 degree turns.

I was considering pouring some draino somewhere along the pipe line and only turning on the shower so that the draino would be drawn to the shower. But I'm not sure if this is possible. I wouldn't want it getting into the drinking water so I'm not sure what the best approach is. Thanks!

Hot, cold or both?

Hot.

Turn off water, remove cartridge. Turn on water briefly to flush out valve body. Disassemble cartridge in sure no blockage in cartridge. Reassemble and reinstall cartridge.

We've run the water without the cartridge in there is no difference between the pressure - so it can't be the cartridge. I'll make sure to verify it is clean but the problem resides somewhere in the pipes as the pressure has gotten weaker and weaker. Thank you for your suggestion.

If you have unrestricted flow out of the ports of the valve (with the cartridge removed) there cannot be a blockage in the pipes leading to the valve. If you have unrestricted cold flow out of the shower head there cannot be a blockage in the riser pipe to the shower head. Not can there be a blockage in the shower head itself.

Only thing left is the cartridge. Did you take the two parts of the cartridge apart to ensure that there is no blockage in the hot side?

P.S.
Water supply pipe don't get blocked. Any blockage in a water supply line will be at a valve somewhere.

We cleaned the shower head out completely. The only thing that makes me think it is something in the pipes is because when we just let it flow out of the tub pipes (no coverings) the pressure is abysmal. Likewise when letting the water flow out where the cartridge is placed the pressure there is terrible as well. I will take the cartridge apart and check it and report back however as I'm no plumber. Thanks again.

The video you referenced is terrible but it does show how dissemble the cartridge. If you do not have full flow with the cartridge remove you may have a blockage somewhere. If so, that would also affect other valves such as the lavatory faucet. If you have a blockage it will be at a valve. Normally there are no valves between the water heater and shower.

I am assuming you have good flow at lavatory faucets.

Not clear here...

If you take the cartridge out and cold water pressure is good then when you turn the water on (hot and cold) pressure should look great (cold would dominate)... UNLESS you are able to isolate the hot vs the cold water using shutoffs?

In that case, if you are able to isolate the hot vs the cold water using a shutoff, then I would suspect that the issue is at the hot water shutoff itself! If you are not using a shutoff then I am still confused, but I might still suspect that the hot water shutoff is the issue here. The valve could be in the wall (near floor) of the shower valve or it could be in the basement. If your shower valve has slotted screws alongside the inlet/outlet to the valves then these are shutoffs and may need to be removed and cleaned to fix this...

Here, to start, I would spend time trying to locate a shut off (if not already using) and then remove the guts of the shut off (if possible), or even cut the shutoff out.

Back to you...

Mark

Just noticed that Harold said,

"P.S. Water supply pipes don't get blocked. Any blockage in a water supply line will be at a valve somewhere."...

And read his last post and it clearly stated the information about the valve (shut off).

Sorry to repeat your info. Harold... but should help Greg be clear on information provided!

I first replaced the cartridge still no water. I then removed the shower head and turned the bent pipe coming out of the wall so the opening was facing up. Then I removed the tub spigot by unscrewing it. Next I Pluged the tub spigot pipe with a cork. I
Then poured about 2 cups CLR calcium and lime remover in the shower head pipe and let it sit for 2 min. Nexted I removed the cork. Then I turned on the water and out it came. Hope this helps I wasted 4 hours trying different things before this.