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applejack 02-09-2013 08:42 AM

Toilet won't flush unless shower is on!

I'm finishing my basement and just installed a toilet and a sink in my bathroom. The sink works fine, but the toilet won't fill with water unless I turn the shower on upstairs! To connect the toilet to the water supply, I removed an elbow joint in the existing shower line and put in a T joint, sending some water up to the shower and some down to the toilet. Now, however, the toilet won't fill up until I turn the shower on. I thought that perhaps the pressure-balance valve of the shower was installed incorrectly, but after breaking the tile in the shower it appears to have been properly installed.

Any idea why there is a vacuum in the line unless I open the shower valve? Any help would be greatly appreciated.

joed 02-09-2013 08:55 AM

Sounds like you tapped into the line after the shower valve. There is no other explanation I can think of.

handyman21 02-09-2013 09:18 AM

You need to tie in to the cold water. You tie in to the shower after the valve that goes to the head. To check turn the shower on to the hot side and go to the water closet and see if the tank is getting hot water to it when it filling. If it is you tie in to the wrong spot.

Javiles 02-09-2013 09:22 AM

I one time seen water come from a light fixture when they turned on the light. yes episode 131 a plumbing we will go the three stooges. :laughing:

joecaption 02-09-2013 09:32 AM

I hooked up a shower valve one time and only had the cold connected and under pressure. I turn on the cold to check for leaks and nothing comes out.
Pulled it all apart to see if there was supply and it works fine, hook it back up and nothing.
Once I connected up both hot and cold it worked fine. The balancing valve was doing it's job.

handyman21 02-09-2013 09:40 AM

Well that fine but if the balancing valve is not working he would have no water at the shower or water closet it not the balancing valve

jagans 02-09-2013 10:31 AM

This one just might take the cake. Amazing!

oh'mike 02-09-2013 10:42 AM

I do hope you took a few pictures of the rough plumbing before the walls were drywalled---

This is a curious turn of events.

applejack 02-09-2013 01:49 PM

Thanks for the suggestions, everyone. I didn't take pictures before drywalling (unfortunately).

I don't believe I tapped into the shower after the valve - I tapped into the line in the basement and I could (at the time) trace the pipe back to the main incoming line - but I wish I had pictures to verify.

Is there any chance that the balancing valve is broken somehow and that is causing a vacuum? Before I installed the toilet, the shower took a long time to warm up and then would get scalding instantly (if you had it turned up too high). I always thought it was just poor insulation in the pipes.

jagans 02-09-2013 02:04 PM

The statement "I dont believe" speaks volumes, as does your UserID. Did you make a sketch of your system with lines labeled and sized before you started cutting and pasting????

Plumbing 101?


handyman21 02-09-2013 02:11 PM

Did you run hot water in the shower and see if there is hot water in the tank?

tribe_fan 02-09-2013 05:05 PM

Sounds like the toilet valve is faulty. Maybe it only works with the reduced pressure.

oh'mike 02-09-2013 05:22 PM


Originally Posted by tribe_fan (Post 1113459)
Sounds like the toilet valve is faulty. Maybe it only works with the reduced pressure.

Shut off the toilet---drain the tank----unscrew the hose from the tank

Stick it in a bucket and turn on the water---have someone turn on the shower and see what happens----------

cleveman 02-09-2013 07:41 PM

What color house is this?

Please list any medications which you are currently taking.

pete0403 02-09-2013 08:23 PM

^^ This. Make sure someone's holding the line in the bucket unless you have a need for a sprinkler in your bathroom.

An easier thing you can do that will tell you the same thing...go up to your bathroom and put your ear near the shower head (make sure the shower has recently been run but is now off), have someone downstairs flush the toilet, listen for gurggling or air sucking into the shower head.

There's nothing creating a vacuum here (nothing in the plumbing anyway) all supply pipes are under pressue unless there is a valve that is off somewhere.

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