Tol

[dougd_in_nc]

I have two toilets in bathrooms that share a wall with one another.

I had a new toilet installed years ago in one of the bathrooms.

However, I have noticed if it's not used for a while, maybe a week or two, then dirty water seems to back up into the new toilet. Is this because it wasn't installed right? What could cause this?

- Doug

 

[Jeff Handy]

The dirty water might just be minerals or algae coming from the toilet tank, or growing in the bowl.
Or minerals or iron in the water, coming out of solution from contact with air.

 

[mrbob]

You're saying there is back-pressure in your system sending effluent into your toilet. Probably, this is happening when someone flushes, causing suction like a syphon.

My understanding is that means that the drain-waste-vent is not working. That involves the fresh-air pipe going out the roof.
https://en.wikipedia.org/wiki/Drain-waste-vent_system
Could that vent be clogged or incorrectly installed?

Disclaimer: I'm not an expert. Hopefully, the better people here will give their thoughts as well.

 

[Jeff Handy]

If you have well water, it very likely is just minerals.