Why does the toilet run when I am using the sink or shower?

Asked Jan 10, 2011, 10:58 AM — **9 Answers**

Every time I use my shower or sink the toilet runs. Help. Thanks

massplumber2008 · Jan 10, 2011, 12:41 PM

Hi Patball...

The washer to the toilet fill valve probably has some sediment in it and needs to be cleaned or replaced.

Check out these links for more info.:

http://www.fluidmaster.com/pdfs/242_instructions.pdf

http://www.fluidmaster.com/index.asp?bhcp=1

If this is not your fill valve let me know.

Let us know if you have questions...

Mark

ballengerb1 · Jan 10, 2011, 01:01 PM

Pat what exactly do you mean it runs. Does it try to fill an already full tank or does the sump siphon down?

massplumber2008 · Jan 10, 2011, 01:36 PM

That's a good point, Bob... could be that the flapper is the issue here, but I would expect that issue to be most noticeable at night when nobody is using water.. ;)

We'll see soon enough...

Mark

pghplumber · Jan 10, 2011, 06:48 PM

Not sure how the flapper is affected by the sink or shower use. More info is needed and remember that sometimes an on site diagnostic is needed to accurately determine the problem. Is this a new problem or has it been going on for a long time? Has there been any work done to the plumbing recently? You could have siphoning through the fill valve if it happens at the same time the sink/shower are used. It could be thermal expansion if it happens a few minutes after using the sink/shower and the hot water tank fires. Is the "running" water going from the fill valve to the tank, the fill tube/overflow tube to the bowl or is it too hard to tell? Check these things or have a pro take a look: 1. Fill valve 2. Backflow device, pressure regulator and thermal expansion tank. 3. Whole house pressure (between 35 and 65 psi. is ideal but some may need up to 75 psi. because of elevation)

profal · Oct 4, 2011, 10:49 AM

Could this issue be related to a clogged vent pipe somewhere - then when water runs below, the internal pressure drops and pulls water through the bowl or flapper?

ballengerb1 · Oct 4, 2011, 10:52 AM

Sorry profal but not in this case. A clogged vent can siphon water out of the bowl but it would not cause the fill valve to open. BTW this is a very old post, sure its fixed by now.

speedball1 · Oct 4, 2011, 11:09 AM

I have had this problem before. Do you hear the ballcock kick on for a second when you turn the lavatory valve on?
Do this for me.
Remove the tank lid and watch the float ball as you open and close the cold water valve on the lavatory.
Does the float ball bounce up and down letting water out of the ball cock. If the answer is yes then I have a solution for you. Let me know, Tom

ballengerb1 · Oct 4, 2011, 03:52 PM

Tom, really old post from last January. Some new person jumped in today but the original is old.

kdaniels11 · Feb 18, 2015, 09:04 AM

Tom: What is your solution in that case, if the float bounces and lets water out of the ball cock? Just curious.

Why does the toilet run when I am using the sink or shower?

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