Geberit to MVHR extraction

[Auchlossen]

I have completed the connection of Geberit to MVHR, so here is the detail FYI.

There seemed to be interest in the JSH and PeterW versions.

Plasterboarding and second fix is delayed, so the fans are not yet functioning, so the ventilation performance is as yet unconfirmed.

 

Geberit model #111.353.00.5 has a Y-branch for extraction of air[smells].

I removed the translucent plastic duct [part of the Geberit] attached to the Y, cut off and Siga taped up the end that linked to the top of the water tank.

 

 

Into the Y was inserted an adapter from 50mm Euro to 1.5" UK [RHS: the most expensive piece of kit in the house @ £12 for a short piece of tube that was 50mm ext and 43mm int diam], followed by two UK reducers. This led via various slow bends through the house in 32mm waste pipe to near the MVHR unit, where it was connected into the standard radial ventilation pipe.

32mm waste pipe was used as it fitted within the service void and was generally unobtrusive and easy to slip in. I did not see that a large diameter pipe was necessary, nor would it have been easy to fit another 75mm pipe in.

http://www.sanifix.co.uk/conversion_fittings.html

Quote

50-43 converter - 50mm male (OD) to 1.5" female (ID) converter bush. Fits straight into a Euro 50mm and allows you to glue 1.5" solvent-weld pipe into it. Only 45mm deep.

Connection to the ventilation pipe was via 50-43mm and 43-32mm reducers [white] and a 50-82mm reducer [grey], which fitted neatly into the ventilation pipe with a rubber sealer ring.

 

Any questions please ask.

[le-cerveau]

@Auchslossen you have done what I am planning:

 With some alterations.

 

Questions:

1. how easy was it to separate the pipe coming out of the Y going up onto the cistern?
2. I presume that is an 82-50mm Solvent weld reducer, 82mm external diameter?
3. What ventilation pipework are you using?

Thanks

Edited January 3, 2017 by le-cerveau

[Auchlossen]

1. Attached to the Y was a push fit plastic moulding, which connected the Y to the water tank. I removed this, cut off the lower part that fitted to the Y because it was in the way of my pipework, and taped off the upper end with Siga-tape, because the top end was a square push fit into the water tank, which it would have been difficult to seal off otherwise. The Y-branch had a sealing ring and some sealing grease on it, which mated well with the waste pipe fittings described previously.

 

2. Yes I think that is right: this was a part found for me by PlumbDrain, described on their receipt printout as 'MLY 82x50mm reducer SRM30:G'. The inside diam was a perfect fit for the ductwork, with a good tight fit when a rubber ring was introduced to make airtight.

3. the ductwork is QuietVent 75mm i/d radial ducting

HTH

[Onoff]

I vaguely remember this discussion way back. Can an older Geberit system be modified, pre installing in the wall to allow for future take off like this?

 

 

[Nickfromwales]

Putting a vacuum anywhere on the cistern will draw air back up the flush pipe. 

Does the cistern have a knock out anywhere to facilitate a connection?

I assume you'd need to look where the newer type have this connection and check to see if you can replicate it. Not seen one myself afaik. 

[Onoff]

So the concept of this is:

 

- The flush pipe has a Y branch.

- Once flushed, there's no more water coming down that pipe. 

- You extract via the Y branch and the smell gets sucked in under the rim of the wc.

 

What's the pipe back to the cistern do? 

 

@Auchlossen, have you got a picture of where it connects to the cistern.

[le-cerveau]

@Onoff, the pipe back to the cistern is for the Geberit odour extract system, that draws air through a charcoal filter, see picture below.

I enquired with Geberit about getting the Y- branch on its own but apparently they are solvent welded into the cisterns, however the cistern with the pipework arrangement below is only £10 more than a standard one, just don't buy the electronic gubbins that goes in the flush plate.

Edited January 22, 2017 by le-cerveau
Picture inserted

[Onoff]

1 hour ago, le-cerveau said:

@Onoff, the pipe back to the cistern is for the Geberit odour extract system, that draws air through a charcoal filter, see picture below.

I enquired with Geberit about getting the Y- branch on its own but apparently they are solvent welded into the cisterns, however the cistern with the pipework arrangement below is only £10 more than a standard one, just don't buy the electronic gubbins that goes in the flush plate.

 

Cheers. Tempted to just put a Y in the downpipe myself and run to a totally separate extract if that's feasible. Maybe with a manual switch.....pressure pad under the seat?

[Jeremy Harris]

It seems I started something when I did this a couple of years ago, as an experiment (and it does work).

 

As Nick says, you don't have to Y into the flush pipe.  The flush pipe is open into the air space above the water level in the cistern, so you can just add a connection to the cistern, rather than the flush pipe.  I used an unused knock out on the side of our cisterns to ft the extract pipes, there is a photo here: http://www.mayfly.eu/housebuild/part-thirty-two-more-on-mvhr-and-nasty-smells/ about three quarters of the way down the page.  Space was a bit tight, so I had to cut things around a bit to get them to fit, and I also have to put some alloy self-adhesive tape around the lid joint to make the cistern a bit more airtight.

 

[dogman]

Will this work with any cistern that has an inbuilt overflow. Wife is not a fan of inbuilt cisterns but i think she would appreciate the extraction facility 

[PeterW]

39 minutes ago, dogman said:

Will this work with any cistern that has an inbuilt overflow. Wife is not a fan of inbuilt cisterns but i think she would appreciate the extraction facility 

 

Yes as long as you can create a negative pressure in the cistern. That may need careful sealing of a standard porcelain cistern lid to the top of the cistern and the addition of an overflow looking pipe - some have this but a lot of modern cisterns only have one entry point.

[Nickfromwales]

Make sure you have sufficient airflow into the cistern to release the water during the flush. 

Most cisterns aren't airtight on purpose, as whatever volume shoots down the flush pipe must be able to flow ( with near zero resistance ) into the cistern simultaneously or you'll get a slow and useless flush with reduced velocity. 

 

I went to a student let once where they were messing with the toilet for whatever reason. I decided to put a small bead of silicone around where the lid sat and bonded it on. A couple of hours later I get a phone call saying the toilet won't flush. Turns out it would flush but the water was slowed down by the vacuum now created in the cistern. Cleared the silicone away from the rear half and it was sorted.

 

@JSHarris I assume ethe mvhr / extract would cope with that issue? Or did you just not go mad on sealing up the cistern?

[Jeremy Harris]

20 hours ago, Nickfromwales said:

Make sure you have sufficient airflow into the cistern to release the water during the flush. 

Most cisterns aren't airtight on purpose, as whatever volume shoots down the flush pipe must be able to flow ( with near zero resistance ) into the cistern simultaneously or you'll get a slow and useless flush with reduced velocity. 

 

I went to a student let once where they were messing with the toilet for whatever reason. I decided to put a small bead of silicone around where the lid sat and bonded it on. A couple of hours later I get a phone call saying the toilet won't flush. Turns out it would flush but the water was slowed down by the vacuum now created in the cistern. Cleared the silicone away from the rear half and it was sorted.

 

@JSHarris I assume ethe mvhr / extract would cope with that issue? Or did you just not go mad on sealing up the cistern?

 

 

Nick, the suction pressure from the MVHR is very low and has no practical effect at all on the flush.  Water being 1000 times denser than air means that you'd need a lot of suction to stop it flushing, probably half way to a vacuum..............

[Nickfromwales]

Not suction . Sufficient airflow through the duct under flush 'flowing' condition. E.g. The equivalent air in to match the volume of water dropping. Can that happily be pulled through the duct IF that's the path it chooses to use to relieve the deficit.? 

[Jeremy Harris]

In my case, the only "vent" hole in the cistern before the mod was the gap around where the cable slot was.  After the mod there's a 1 1/2" pipe fitted to the side with a very low suction on it.  At a guess, there's probably the capacity for at least an order of magnitude better air flow into the top of the cistern now than there was before. 

 

A conventional, non-built in, cistern, can have a fairly tightly fitting lid, in which case the only ventilation is via the overflow pipe, which is around 18mm bore.

 

Anyway, I did this a couple of years ago, and both cisterns flush just as well as they did before the mod, so it doesn't seem to have any impact at all on flushing, and a test is always better than a bit of theory!

[Onoff]

Not sure I've an extra hole anywhere that can be widened/enlarged:

 

 

 

 

This "Y branch" thing is interesting, it's clipped to the blue frame and capped as far as I can tell,  no idea what the point of it is though:

 

 

It comes up inside the cistern above the water level:

 

 

Maybe I should read the instructions!

[le-cerveau]

@Auchlossen, what brand of MVHR ducting are you using?

[Auchlossen]

75mm QuietVent red radial ducting - a stub of it is shown in the third pic in my original post.

[Onoff]

Really keen to do something like this and pretty sure the wife and kids would really appreciate it too!

 

So....as I understand it I need for a start to introduce a Y branch into the flush pipe that comes down from the cistern? As best as I can ascertain (lost my vernier so circumfrence/Pi) it's 56mm dia. No idea what it's made of though.....some kind of "styrene"?

 

 

Looks like it is solvent welded?

 

 

So the way this works; when you flush water comes down the flush pipe, past the Y branch and "clears the contents". When the flush pipe doesn't have water coming down it the "smell" can be extracted from the pan via the branch?

 

So wondering if I could add in a generic solvent weld branch like this:

 

http://www.toolstation.com/shop/Plumbing/d20/Plastic+Solvent+Weld/sd2885/Solvent+Weld+135°+Branch/p23092

 

What sort of an idiot would start hacking into a perfectly good Geberit???

Edited February 19, 2017 by Onoff
T'station link etc

[PeterW]

1 hour ago, Onoff said:

What sort of an idiot would start hacking into a perfectly good Geberit???

 

Errrr ... you're better off putting the cistern under negative pressure - just add another tank connector above the water line (in the lid...?) and it will extract via the flush pipe. 

 

Cutting and welding unknown plastics is a REALLY bad idea ... 

[Onoff]

2 hours ago, PeterW said:

 

Errrr ... you're better off putting the cistern under negative pressure - just add another tank connector above the water line (in the lid...?) and it will extract via the flush pipe. 

 

Cutting and welding unknown plastics is a REALLY bad idea ... 

 

Ta. Was the just as worried about drilling the cistern in case it cracks or crazes. All I can find on Geberit sites is it's "one piece blow moulded plastic". So what sort of diameter should I be thinking about?

 

(Tempted to try a teensy weensy drop of solvent weld on something that won't show to see if my Y branch mod would work).

Edited February 19, 2017 by Onoff
(Tempted.....).

[le-cerveau]

I looked at this and researched it extensively, including numerous enquires with Geberit.  They don't sell the Y pipe separately, and as you say the current down pipe is welded in, however the cistern with the Y pipe in is only £10 dearer than the standard on, so if you plan ahead and fit the odour extract cistern without the electronic gubbins and then retrofit later.

 

I know this doesn't solve your problem so I suspect the best (and safest) solution is to take the air out of the cistern, above the fill level (aka JSH) so as to not compromise the cistern.

[Onoff]

Wondering if I could just drill a 20mm hole in the top somewhere and fit a M20 gland and length of flexible 20mm conduit (parts I've already got) running up to the loft? Then a small passive IR detector/occupancy sensor that kicks in an inline fan when you're on / near the wc. 

 

What's a test for this, light a plastic drinking straw, hold down the pan and see if the smoke gets sucked up?

Edited February 20, 2017 by Onoff
"What's a test for this......

[le-cerveau]

From what I understand, most people doing this are plumbing it into the MVHR so there is permanent extract.  If you are adding a separate fan then that is new territory and I suspect you will need to ensure that it does not extract too much!

[Jeremy Harris]

19 minutes ago, le-cerveau said:

From what I understand, most people doing this are plumbing it into the MVHR so there is permanent extract.  If you are adding a separate fan then that is new territory and I suspect you will need to ensure that it does not extract too much!

 

 

The separate fan ones were what gave me the idea to plumb the pan to the MVHR, as they've been around for some time.  The idea originated with a Malaysian company, GBH Group, and they still manufacture the original "Odourbuster" (that a couple of chancers on Dragon's Den claimed was their own product!).  The brochure on that system is here: http://gbhgroup.com.my/images/product/bathroom/latest-products/odourbuster/odourbuster.pdf  It's a bit complex for what it is, and there are other systems that just connect direct to the cistern, but with a fan and a carbon filter to remove the odour.