Toilet fills when filling water tank

[larslo]

Hi there

I replaced my water pump in my 2018 3901mb this summer. Works great. Today I tried to fill my fresh water tank. Water keeps filling the toilet in the master bath. Doesn’t do that when connected to city water connection

Any thoughts as to why this is happening?

[mhs4771]

Is your Black now Full?? Sure sounds like you hooked up to the Black Tank Flush port instead of the Fresh water Fill port.
There should be no way for water to fill the toilet when connected to the Fresh Water Fill port unless something is cross plumbed.

[travelin' texans]

Originally Posted by larslo

Hi there

I replaced my water pump in my 2018 3901mb this summer. Works great. Today I tried to fill my fresh water tank. Water keeps filling the toilet in the master bath. Doesn’t do that when connected to city water connection

Any thoughts as to why this is happening?

The toilet is not/should not be directly connected to either of the water sources to be effected by the filling, so that shouldn't be the issue.
Do you have a Thetford Aqua Magic toilet? If so they are well known for leaking & filling when unwanted. Parts are also expensive & in most cases the toilet needs to be removed to work on them.
My recommendation is to replace the POS Thetford with a Dometic 310 (round bowl) or a 320 (elongated bowl) & while doing so add a shut off valve behind the toilet.