Some sort of toilet blockage causing back up into shower.

[8misskitty8]

Having a terrible Sunday. Had a new shower cubicle installed a couple of weeks ago, everything seems ok.
Today I took off the shower drain cover and found it full of brown water.
Investigating further it Seems when the toilet is flushed some water goes up the shower drain 🤢
The toilet is in the opposite corner right beside the main waste pipe.
We have a toilet next door which is connected to the same main waste pipe and nothing appears in the shower when that is flushed.
I don’t know how long this has been going on as the previous cubicle you couldn’t remove the drain cover at all. The shower room toilet has always had a crap flush as the council planners insisted it be one of those toilets that use less water and we often have to flush a couple of times even after a pee to get it to all go.
Is it just we’ve got a rubbish toilet or am I looking at thousands to rip my shower room apart ?

Either a blockage or the waste pipes have been installed incorrectly at too shallow a drop and therefore water backing up. Impossible to say really. If you’ve tried the usual things such as drain blockage clearing products (mr muscle etc) to no avail then maybe it’s to do with the actual piping. Have you only just noticed? Not noticed any foul smells for the last however long?

Call back whoever did the work two weeks back?

The shower itself isn’t backing up as the water runs away fine. When I run the sink taps nothing goes into the shower.
The previous shower tray didn’t have a removable drain like this one has so I have no idea if it’s been doing this previously or it’s just happened.
The toilet in there generally doesn’t get used very much either as the flush is rubbish.
Ive tried mr muscle down the shower and the toilet but it didn’t make a difference.

I’ll contact the company that put the shower cubicle in tomorrow but I was hoping there might be a quick fix that i could try.