Shower Drips when Toilet Flushed

Hmm, mysterious.

In our master bathroom, the toilet is next to the shower.

When the toilet is flushed, the shower drips water until the toilet is filled again.

Mysterious indeed.

I (we) put up with this for a few months thinking it may just be a fluke and go away.

I had a plumber out to handle another issue and remembered this issue. I asked the plumber about it and got a blank stare. He looked at it and said, “huh”.

Not the confidence builder I was looking for.

2 weeks later I decided to search more on this internet thing for an answer.

There is a bunch of garbage advice out there for this strange shower dripping problem.

Then I found this answer and it got me thinking.

The gist is this: newer faucets have a safety feature that has various names depending on your faucet brand.  Mine turns out to be a Price Pfister.  They refer to this safety feature as “pressure balancing”, some call it scald protection.

You know that issue of a nearby toilet flushing causing the shower to get hot?  This is caused because when the toilet is refilling, it is using cold water…taking cold water from the shower and making your perfect temperature shower now HOT!

To minimize this there is the pressure balancing feature.

Quite simply this means, if a toilet near the shower is flushed there is a spring loaded valve that senses a reduction in cold water pressure, and opens allowing more cold water through to prevent the water from getting too hot.

So, over time that spring gets weak.  When that spring gets weak, and it sense a drop in cold water pressure…from say…a toilet flush, that spring lets the valve open and water drips out of your dang shower.

Now, understanding this it finally makes sense.

FYI: I’d say our shower faucet is about 4 years old.

I’m not going to go into removing the handle and faceplate from your shower, but once I did I saw what I figured I needed to replace.

Behind the faceplate was this getup.

The actual valve assembly black plastic part.  You simply remove 4 screws and it slides off.

I ran to the hardware store and got a new one.

I got home, it took about 10 minutes to swap out and…still drips.

Damn.

I looked closer inside saw another part.  Turns out that is called the cartridge.  I figured this was where the magic happened.

This is the cartridge:

I ran back to the hardware store and bought that part.  10 minutes after returning home and PRESTO — Leak FIXED!

Yep, I probably didn’t need to replace the valve stem, but I didn’t now any better.

Hope this helps somebody out.