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Shower connected to macerator not draining fast enough

Postby crusoe » Fri Jan 20, 2023 1:39 pm


Thanks for taking the time to read:

I've got an on-suite with a macerator, and a toilet, shower and sink all connected to the macerator. The setup has been working perfectly until recently when a toilet flush would send waste up into the shower.

I removed the macerator and cleaned it out (fun job) and replaced it all and the problem persisted. I figured it was the macerator that had packed up so I bought a new one (sanislim) and plumbed that in. Now, when I flush the toilet nothing comes up in the shower, and running the tap the macerator works and the water disappears. However, turning the shower on, the water doesn't drain fast enough and the shower starts to flood.

I figured since the toilet and tap are working now that there must be a blockage between the shower and the macerator, so disconnected the macerator, and connected my wet vac to the pipe and turned the shower on - the water flowed freely and the shower didn't flood. As soon as I reconnect the macerator the shower floods again. I'm not entirely sure the pipe between the shower and the macerator has the required 3 degrees drop, but it was working before so should be working with a new macerator (like for like replacement).

So I'm pretty stumped right now! All I can think of is that there is a blockage in the pipe that the macerator discharges into, and that neither the toilet nor the tap produce enough water for the blockage to matter but the shower does?

Would appreciate any advice or tips! Thanks for reading
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Simply Build It

Postby stoneyboy » Mon Jan 23, 2023 9:30 pm

Hi crusoe,
Have you checked the shower trap for blockages.
Regards S
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Postby crusoe » Tue Jan 24, 2023 9:04 am


Yes, I've checked and the water flows freely from the shower if I disconnect the macerator. It's a head scratcher for sure! The only pipe I've not checked is the discharge pipe in the roof, but if that was blocked then surely I'd have the same issue with the toilet and the basin.

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