Macerator discharge pipework query (not actually a Saniflo)

[GwyneeJ]

I'm installing a macerator (like a Saniflo but cheaper) for the en-suite. The discharge pipework is 32mm solvent welded waste pipe, with a 3 metre vertical lift into the roof space and then 8 metres falling by gravity at a gradient of 1:30 to the soil stack.

Question is should I fit an air admittance valve at the start of the gravity section? The instructions don't require it but I'm just thinking it might help the 'gunk' to clear better.

Any thoughts?

[Dicky99]

I'm installing a macerator (like a Saniflo but cheaper) for the en-suite. The discharge pipework is 32mm solvent welded waste pipe, with a 3 metre vertical lift into the roof space and then 8 metres falling by gravity at a gradient of 1:30 to the soil stack.

Question is should I fit an air admittance valve at the start of the gravity section? The instructions don't require it but I'm just thinking it might help the 'gunk' to clear better.

Any thoughts?

You need to apply for Building Regs approval and follow the requirements of the relevant approved documents. If in doubt about application ask the BCO because you'll need to have a completion certificate from him/her on completion for your records.

[Mike4]

I'm installing a macerator (like a Saniflo but cheaper) for the en-suite. The discharge pipework is 32mm solvent welded waste pipe, with a 3 metre vertical lift into the roof space and then 8 metres falling by gravity at a gradient of 1:30 to the soil stack.

Question is should I fit an air admittance valve at the start of the gravity section? The instructions don't require it but I'm just thinking it might help the 'gunk' to clear better.

Any thoughts?

A three metre vertical pipe 32mm in diameter permanently full of sh1t?

Rather in your house than mine, when that box eventually fails!!


If ever there was a piece of machinery in a house NOT to cheapskate on, the Saniflo would be IT, (in my personal opinion). If you really must have one at all.

[kempiejon]

I'm installing a macerator (like a Saniflo but cheaper) for the en-suite. The discharge pipework is 32mm solvent welded waste pipe, with a 3 metre vertical lift into the roof space and then 8 metres falling by gravity at a gradient of 1:30 to the soil stack.

Question is should I fit an air admittance valve at the start of the gravity section? The instructions don't require it but I'm just thinking it might help the 'gunk' to clear better.

Any thoughts?

A three metre vertical pipe 32mm in diameter permanently full of sh1t?

Rather in your house than mine, when that box eventually fails!!


If ever there was a piece of machinery in a house NOT to cheapskate on, the Saniflo would be IT, (in my personal opinion). If you really must have one at all.

Argh, repressed memory from 30 years plus. Chum in a dark grotty basement bedsit with [expletive deleted] muncher. Never heard of such a thing before, not only did it go up it also went all along the wall of the flat - at ceiling height. Then it failed and all came out under pressure. I was just visiting and couldn't just leave them could I.

[tacpot12]

I'm not a plumber and have no expertise in this area, but for what it's worth, I wouldn't install a AAV.

I would say that there is too much risk of it failing (leaking) and raw sewage being pushed out under pressure from the pump. I think it would be better to have a wider pipe for the gravity section, e.g. 50mm, to allow air from the sewer to flow up to the highest point. If the gravity section is left as 32mm, it seems more likely that it could clog under pressure from the pump. I agree that finding a way to get air to the top of the gravity section is a good idea.

This video (at around 9:55) deals with the problem of air on the pumped side of the piping, where air in the pumped side needs to be exhausted to atmosphere: https://youtu.be/eHAsuPVBwYM?si=EXGxKbJKjZH8SR4G

The video gives some insights to the problems you are trying to deal with.

You could also ask your question on this forum where you will get more knowlegeable answers: https://www.ukplumbersforums.co.uk/

[Gwynee]

I'm installing a macerator (like a Saniflo but cheaper) for the en-suite. The discharge pipework is 32mm solvent welded waste pipe, with a 3 metre vertical lift into the roof space and then 8 metres falling by gravity at a gradient of 1:30 to the soil stack.

Question is should I fit an air admittance valve at the start of the gravity section? The instructions don't require it but I'm just thinking it might help the 'gunk' to clear better.

Any thoughts?

A three metre vertical pipe 32mm in diameter permanently full of sh1t?

Rather in your house than mine, when that box eventually fails!!


If ever there was a piece of machinery in a house NOT to cheapskate on, the Saniflo would be IT, (in my personal opinion). If you really must have one at all.

Total volume of the pipe contents will be around 2.5 litres, so less than you might think. And I intend to include a drain plug near the bottom so it can be drained safely into a bucket when necessary.

Unfortunately we have no choice about having a macerator, the en-suite was built with a Saniflo years ago and I hate it! I've tried to think of ways to install a proper 110mm waste, to no avail. We seem to be replacing the Saniflo every 5 years or so, at a cost of about £600, and the cheapo version we have now bought does get good reviews. If it only lasts a couple of years it will still be less costly per annum than Saniflo.

[bungeejumper]

Just for old time's sake, here's a thread from 2018 in which several of us outed ourselves (although I'd escaped the monstrous beast) and shared a few fun stories. viewtopic.php?t=11212

I had a more recent encounter with a plumber who was installing an expensive medical gizmo with a very similar (ahem) purpose and function in one of our commercial properties. He was using 40mm pipe throughout, but he'd chosen right angle elbows rather than swept bends. I asked him why? Because it's neater, he replied. I hope our client won't come to regret that?

BJ

[9873210]

A three metre vertical pipe 32mm in diameter permanently full of sh1t?

Rather in your house than mine, when that box eventually fails!!

Total volume of the pipe contents will be around 2.5 litres, so less than you might think.

'tis not so deep as a well, nor so wide as a church-door, but 'tis enough, 'twill serve

I've never had the pleasure of dealing with liquidized ****. But I have dealt with liquids like blood, petrol and milk. A few microlitres of blood can ruin a dress shirt. A few cc of petrol can render a room uninhabitable for weeks. Spill a pint of milk on an absorbent surface and it will never be the same again.

IMHO 2.5 L of liquid **** in a floor cavity above a plaster and lath ceiling would be most unpleasant. I'd really want a secondary containment system.

[Mike4]

Spill a pint of milk on an absorbent surface and it will never be the same again.

And on that note, don't ever accidentally allow a packet of butter to fall out of your shopping bag onto the back seat of your car during a heatwave then leave the car in the sun for a week.

DAMHIK!

[bungeejumper]

Spill a pint of milk on an absorbent surface and it will never be the same again.

And on that note, don't ever accidentally allow a packet of butter to fall out of your shopping bag onto the back seat of your car during a heatwave then leave the car in the sun for a week.

I reckon I can beat that. I once bought a used car which arrived smelling heavily of air freshener - but which succumbed within a fortnight to the unmistakeable scent of baby vomit.

It took me weeks to scrub the smell away. These days I'd have done the job in half an hour with my trusty wet-and-dry vacuum cleaner. (Soak, suck, repeat.) Note, do not attempt this method after a petrol spill.

Yes, a ceiling full of sh*t would take a bit of dealing with. One of the few things that can beat the pervasive pong of a dead rat under the floorboards. Again, DAMHIK

BJ

[the0ni0nking]

This is not answering the original question but just some observations.

In my own house, I have a macerator following the installation of an en-suite to one of the bedrooms. The house is a strange set-up but the macerator itself is located in the garage and the en-suite it supports is behind a breeze block wall. (Basically the garage was so long it could easily lose a couple of metres to provide an en-suite to one of the bedrooms located on the ground floor). That macerator has been in place now for c10 years and other than one incident has worked fine. The incident involved required the use of a wet vac to clear it which was unpleasant but was something I did rather than pay someone). It also basically just has to push the “material” sideways into the main soil pipe located probably c7m away.

In one of my rentals, there are two both of which have to push material vertically. These have caused no end of issues. I’d need to check my paperwork which is in the UK and I’m currently in Spain so am unable to do so but I suspect there’s been at least 4 replacements over the last decade and numerous plumber call outs to resolve issues. It got to the stage where I started to believe the plumbers the agents were using were just rubbish so I paid for a registered Saniflo installer to travel c50 miles from a neighbouring county to look at them.

He basically said the installation was flawed and he’d refuse to install a Saniflo unless he could also rip out a host of pipework that was too narrow for its intended purpose. Since then, I’ve accepted the fact it’s a make do and mend approach as and when issues arise.

Why am I posting this - well if only to say that if I had the time again, I’d pay more to make sure the initial installation is done properly. Better that than have ongoing reactive maintenance or replacements which in my case have probably cost me maybe £4-£5k over the last few years.

[AshleyW]

I have a property with a lower ground floor with a sewage sump pump system to pump the waste up to the drainage at street level. There is a rise of about 4m with 2" pipe. My only regret was not putting a stop valve at the bottom of the 2" pipe. So when the pump eventually failed all the muck in the 4m run discharged itself on top of me! Some lessons are learned the hard way!

[Gwynee]

Follow-up having finished the job, for anyone who is interested...

I decided not to bother with an air admittance valve following advice here, thanks. The installation seems to be working fine without it.

I included a tee off with an access plug at the bottom of the vertical pipe so I can drain the contents into a bucket if I need to do any maintenance work. Preferable to draining it into my face, I think!

The old Saniflo, with 21.5mm discharge pipework, used to take about a minute to pump away a toilet flush. The new unit, with 32mm pipework, takes about 5 seconds. So far, I'm happy with the completed job (and more importantly so is 'er indoors!).

Cheers all.