Macerator

[ppppenguin]

There's a non-return valve in most if not all macerators to stop that happening. Obviously if you flush when there's no power and there's a vertical run the pan will fill with water.

[pwdrive]

There is indeed, pretty pointless advertising them otherwise.

Lawrence.

[ppppenguin]

I've decided to use 32mm solvent weld pipe with swept bends and rodding eyes. Why not 21.5mm? There don't seem to be swept bends and rodding eyes available. Vertical run indoors to reduce the chance of freezing. For the connection to the cast iron soil stack I'm going to try a standard strap-on boss. I'll see if I can tighten it up to fit the smaller size pipe or at least put some padding in so it tightens OK. Then silicone to make a seal.

[pwdrive]

You should be able to get a reducer adaptor to fit those grey plastic clamp on bosses they normally come with a sealing ring fitted.

Lawrence.

[ppppenguin]

Lawrence, I may have misunderstood you here. No problem connecting the 32mm (or even 21.5mm) pipe to the boss. The problem is that standard plastic soil pipe is rather larger diameter than cast iron. Hence the boss won't clamp on to it very well. Even if there's enough adjustment range when tightening the strap the flange likely won't sit very well on the soil pipe. The strap tightening problem can be solved by carefully placed packing. The flange seating looks like a bodge with silicone.

[pwdrive]

Ok, got that, with you now.

Lawrence.

[boater sam]

Sorry, but that is wrong. The design is such that the box will hold one 6 litre flush of water even with the motor not running.
The pan will show a high water level, warning the user that it is not working. If the flush is again operated, the pan will hold another 6 litres.
Note that all these units were intended foe 6 litre cisterns, our old 9 litre is really too big and wastes water.

[boater sam]

Alan, I am curious as to what make the American macerator was, I have never heard of one from across the pond.

[Doodlebug]

We also have a sink and bath connected to ours.
So the risk of flooding due to any vert rise would have been risky.
That is another reason why I didn't use any vert runs.

The one way valve would not help as it is only used to prevent waste in the
unit going back down the pipes feeding the macerator.

[ppppenguin]

In many cases you can't avoid a vertical run. For example in a basement below the main drain level. In theory I could do without a vertical run but the route would be very convoluted and difficult.