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DIY toilet odour removal idea


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#1 jsharris

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Posted 26 January 2014 - 02:55 PM

Prompted by a question asked on my blog, I've been looking at all the many and various direct toilet pan ventilation/extraction system.

Probably the best known is the very expensive unit unit that's marketed in the UK as the Odour Buster (but which is very clearly either a re-badged or just imported far-eastern unit - they've been on sale there for years, despite them being on Dragon's Den). This costs around £200, which is a crazy price for what it is. It works by drawing air from around the pan when it's in use and pumping it into the foul drain, via a one-way valve and a very low power fan. OK, but a bit complex, in my view.

Next are the many and varied units that connect a fan to the cistern and utilise the internal overflow pipe that connects directly to the back of the toilet flush pipe. Some of these have electric fans and cartridge filters that sit inside the cistern and which turn on via a proximity sensor, some connect to the air space above the cistern and have a small external fan that exhausts to the outside of the house, via a small duct (typically around 1.5" to 2"). These only need a small fan because the volume they are extracting from is small, perhaps 20 litres at most (it's just the internal volume of the toilet bowl with either the lid down or someone sat on the seat). A fan that can extract at just a litre per second would be more than adequate to pull any odour out of the toilet basin. These units are fairly cheap, the one that has a fan and filter cartridge inside the cistern is around £20. The snag is you need to replace the cartridge every year, as it relies on something like activated charcoal as an odour filter.

Whilst looking at these I had an idea. If you have a house with MVHR, then you already have a continuous extract system. Simply connecting a bit of small bore duct from the top of the cistern to the nearest extract duct would ensure that air was extracted (via the cistern internal overflow pipe) to the MVHR exhaust.

As we're fitting built in units, with internal cisterns, it should be easy to drill holes in the plastic cistern lids and connect them up to a bit of waste pipe to act as a duct. In our house I have a space in the eaves right behind both bathrooms that can take these ducts and feed them to the MVHR extract manifold pretty easily.

My guess is that I can probably ventilate both toilet basins via the MVHR for less than £20 in parts. I shall report back when the house is finished as to how well this idea works!

Edited by jsharris, 26 January 2014 - 02:56 PM.


#2 ProDave

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Posted 26 January 2014 - 03:11 PM

Sounds like a good plan.

Most close coupled toilets don't actually have an overflow pipe, but instead overflow down the flush pipe into the toilet if the inlet valve fails. So there's no ready place to connect your extract duct to with those.

But in the case of concealed plastic tanks, it would be easy to drill a suitable hole in the plastic lid for instance.

This might be something not to mention to building control?

#3 Nickfromwales

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Posted 26 January 2014 - 03:18 PM

Would you then have two points of extraction in these rooms? Or are you considering just the pan extract point as sufficient for the cloakroom and then two points of ext in the master bathroom? I appreciate your in a good position with the vanity units and existing MVHR but would joe public be ok with a regular extractor do the same, if not better as they have quicker ext rates ?
FYI, I fit the ext kits that have timers and back draught shutters, or the wall mounted ones with an actuator to open/close an iris so as to stop excess room ventilation / draughts.

#4 jsharris

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Posted 26 January 2014 - 03:25 PM

I agree about not mentioning this to BC!

We're fortunate in that we're using concealed cisterns in all the toilets, built in to units, so they will all have the overflow as a standing pipe inside that connects down to the flush pipe.

Nick,

The idea behind these units is to draw a very small volume of air directly from the toilet pan (via the flush pipe) to remove odours at source, as they are created. This isn't a substitute for WC or bathroom ventilation, but an addition that solely deals with toilet odour. Have a look at the (expensive) Odour Buster website here: http://odourbuster.com/ to get an idea as to how their system works, or the very much cheaper Pan Fan here: http://www.panfan.ca/How_it_Works.html .

My idea was to mimic the way the Pan Fan works but just use the extract side of the MVHR to provide a bit of suction right where it's needed.

#5 ProDave

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Posted 26 January 2014 - 03:27 PM

We all await the results of a scientific test the morning after you have had a curry. :wacko:

#6 jsharris

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Posted 26 January 2014 - 03:33 PM

With me it'd be certain varieties of beer - I seem immune to curry................. :unsure:

I've spotted that you can but the Pan Fan here: http://www.ebay.co.u...=item257bcc7b76 for less than £25, but it's the basic model that needs to be recharged every few weeks and has to be manually switched on and off when used.

#7 Nickfromwales

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Posted 26 January 2014 - 04:34 PM

Wonder if they do a bog standard kit :-D

#8 temp

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Posted 26 January 2014 - 04:45 PM

Seems like a great idea. The two cisterns we have both use European style lifting tube valves to let the water out into the pan. In the event that the water inlet valve fails the water level rises and overflows flows down the centre of the tube. So yes I think you would only need to connect an mhrv extract pipe to the top of the cistern and it would suck air out of the pan.


#9 Alphonsox

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Posted 26 January 2014 - 06:51 PM

Three pints of Hop Back's best Ales, a vindaloo and an air flow meter - calibration should be fun!

#10 ProDave

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Posted 26 January 2014 - 07:04 PM

The IR thermometer may play a part in the analysis as well.

#11 brickie

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Posted 26 January 2014 - 10:30 PM

You're right about BC-the s75t could really hit the fan!
(No way I could let that one pass,sorry!)

#12 NeilW

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Posted 27 January 2014 - 07:00 PM

Won't the MVHR extract in the wet rooms just deal with the odours by itself?

#13 ProDave

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Posted 27 January 2014 - 07:25 PM

The point of "evacuating" the toilet is the smell never leaves the toilet, not even into the room.

#14 jsharris

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Posted 27 January 2014 - 07:27 PM

 NeilW, on 27 January 2014 - 07:00 PM, said:

Won't the MVHR extract in the wet rooms just deal with the odours by itself?

Welcome to the forum.

Yes and no. The bathroom/WC extract will draw the odours from the toilet very slowly towards the outlet (typically it'll take around two hours to change all the air in the WC/bathroom). This simple mod should extract the 20 litres or so of air in the toilet bowl in around 20 seconds or so, which (I hope) should stop odours even escaping into the room.

This is the aim, to get rid of the odours at source, before they diffuse into the room. This should mean that the room stays fresh, so if someone uses it within a few minutes of someone else, with luck there shouldn't be any odour.

[edited to add that my reply clashed with Dave's, who's made the same point]

Edited by jsharris, 27 January 2014 - 07:28 PM.


#15 vk2003

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Posted 16 August 2014 - 04:40 PM

The only thing I would worry about with connecting your mvhr to the toilet pans, is the bacterial aerosol load that will get drawn up into your system/manifold. Have you put an inline filter in to prevent this?

#16 jsharris

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Posted 16 August 2014 - 05:14 PM

I'm not sure this is really a problem, as the pipe just connects to the extract plenum right next to the MVHR. It's only pulling air gently from the top of the cistern (an air space that's connected directly to the flush pipe via the internal overflow), so cannot actually extract during the flush, as the flush pressure will massively exceed the very slight depression that the MVHR can provide. My guess is that this will mean that all the flow is down and out to the drain during the flush and the cistern water refill will also probably tend to push air in the overflow downwards, expelling any short duration aerosol to the drain. The length of ducting down to the MVHR plenum is probably enough to ensure that any remaining coliform bacteria get dried out, as they can't survive for long in dry environments. They are also anaerobes, so wouldn't much like being in an oxygen-rich air duct. Finally they aren't able to cross-contaminate anything anyway, as the extract side of the MVHR is completely isolated from the fresh air supply side.

There are a fair few kits around that are basically just fans that slightly de-pressurise the cistern air space when they detect that the toilet is about to be used (they often seem to use a PIR sensor or similar to turn the small fan on) and discharge the air via a vent, which is essentially all I'm doing with the MVHR extract. None of these kits seem to use any filters if they have an external extract, although I have seen some that use an activated charcoal canister to allow the discharge air to be fed back into the room. If there was a realistic possibility of bacterial growth occurring then I think these activated carbon units would probably be prime candidates, but my guess is that it isn't a problem because of faecal coliform bacteria being anaerobic and so unlikely to grow on a filter with a lot of air flowing through it.

#17 SteamyTea

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Posted 16 August 2014 - 09:47 PM

 ProDave, on 26 January 2014 - 07:04 PM, said:

The IR thermometer may play a part in the analysis as well.
This just reminded me of the difference between an oral and an anal thermometer.

The taste

#18 joiner

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Posted 17 August 2014 - 06:57 AM

:rolleyes:

#19 coopers

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Posted 20 August 2014 - 06:53 AM

Now Jeremy. For your next challenge, please can you invent a heated toilet seat system. They are available in USA /Canada at great expense. I'm sure there's a market for them here, with all the under-insulated housing stock and icy bathrooms. I can just see Jeremy presenting this on Dragons Den :P

hi guys, I haven't been on the forum for ages...losing the will to live/build <_<

Suzanne x

#20 notnickclegg

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Posted 20 August 2014 - 01:09 PM

 coopers, on 20 August 2014 - 06:53 AM, said:

For your next challenge, please can you invent a heated toilet seat system.

You are my wife and I claim my £5.

Jack