Help with macerator outlet

[JimLoskot]

We have a saniplus macerator in the en-suite of the attic bedroom. Who-ever installed it did a bad job of it.
I have unkinked the outflow pipe and straightened the pipe work up (yes I know it shouldn't be 25mm MDPE pipe but I'm stuck with it untill I rip it all out next year) see picture below:

Macerator outlet

• JimLoskot
• 22 Jun 2012
• 1

What I need some help with is:
because the waste flows downhill I need an air admitance valve somewhere to stop it syphoning waste back up, however I've not been able to find anything like this for 25mm pipe.
I'm after a relatively cheapish and quick (days labour) to sort this out so it lasts about a year.
Any suggestion and where to get the parts please that don't involve replacing the whole of the outlet pipe.
I've had the saniflo out and cleaned it all up and it looks in good working order

 

[swbjackson]

There should be a non return valve in the outlet of the macerator. This will prevent any backflow into it.

 

[75pete]

Yes that is what you need. On mine it lives in the outlet elbow that you connect to the unit, then after, you run the pipe to the stack.

 

[JimLoskot]

thanks, I think I have one.
The problem is I can hear it bubbling air back into when it has finished pumping. I presume this is because it is running downhill although the manual only says considerably lower and our runs a little bit lower so not sure if this is the problem:

If the discharge pipework runs to a level considerably lower than the unit, the resultant siphoning effect can suck out the water seal in the
unit. Fitting an air admittance valve capable of withstanding 10psi pressure (BBA approved) at the high point of the pipe run will overcome
this problem.

There is also a bit of a smell every now and again but I think this may be down to a poor sink trap