Jeremy Harris Posted August 26, 2019 Share Posted August 26, 2019 Some may recall that I fitted an odour extraction system to our bathroom toilets, to suck air directly from under the seat, using the flush holes in the rim. The effectiveness of this has just been commented on again, so I thought it worth doing an update. For those that didn't see the original posts on this (I've a feeling they may well have been on this forum's predecessor, so now lost) I decided to plumb the space above the cistern on each WC to the MVHR extract ducting, using 40mm waste pipe. This air space is directly connected to the flushing water outlets under the rim for any WC that has an overflow that discharges to the pan (as the majority of newer ones do). It was an easy modification, just a hole cut in the side of the cistern, well above the water level, and a bit of pipe fitted: Although the air flow rate is pretty low, it's remarkably effective. Literally no odour escapes from the pan at all. In our case, it was very easy to install, as both cisterns backed on to the wall where all our eaves services run, so running a length of extract duct along there and plumbing it in to both cisterns was just an hour or so's work. Well worth it, in terms of the benefit this system gives, IMHO. 2 1 Link to comment Share on other sites More sharing options...
ToughButterCup Posted August 26, 2019 Share Posted August 26, 2019 Over the years I've been bought a few pints telling your story . Nobody believed me. Now, I can refer them to the post about it...... 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2019 Author Share Posted August 26, 2019 It's surprisingly reassuring to leave the bathroom after a particularly malodorous event, secure in the knowledge that you've not left anything behind that might cause offence to the next user. Not just me that's feels this way about it either, it was commented on earlier today, hence the reason for deciding it was time for an update. Link to comment Share on other sites More sharing options...
Onoff Posted August 26, 2019 Share Posted August 26, 2019 (edited) I was only "sitting"' contemplating this this morning. I REALLY need to get my ar$e in gear and fit a fan to my unfinished pan take off system. My youngest has, on occasion, slid an A4 sheet under the door whilst I'm in there with the word "SMELLS!" scrawled with a Sharpie. 32mm solvent weld fitting into the top of the Geberit cistern. (Not sure tba whether this will impede servicing but I can always multi-tool it flush). At the mo the take off pipe just ends in the loft: Edited August 26, 2019 by Onoff 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 26, 2019 Author Share Posted August 26, 2019 Just stick a small computer fan on the pipe and see what happens. My guess is that it will work fine, as I don't think that the airflow rate on ours is very high at all. I think the secret is that there's only a small volume to ventilate, and only a relatively small volume of "smelly stuff" to remove. A couple of air changes of the pan air volume might be enough to get rid of 90% of the odour. Link to comment Share on other sites More sharing options...
Onoff Posted August 26, 2019 Share Posted August 26, 2019 Anyone know of a very short range PIR sensor that would only trigger when someone sits on the pan? Link to comment Share on other sites More sharing options...
Tennentslager Posted August 26, 2019 Share Posted August 26, 2019 At the hut I have a laptop fan running on a leisure battery powered from one solar panel (draws 0.1amp) 24 hours a day, vents under the floor. Now, given this is a dry toilet this means the smelly stuff is in situ so to speak and there’s no smell whatsoever Link to comment Share on other sites More sharing options...
andyscotland Posted August 26, 2019 Share Posted August 26, 2019 Very interested in this for the ensuite in my garage conversion. I won't have an MVHR, do you think it would be feasible to link it into the extract somehow? Planning to fit an inline ducted fan so I could possibly boss into that with some kind of flow restrictor? Or would that risk causing noise/other issues? Link to comment Share on other sites More sharing options...
Onoff Posted August 27, 2019 Share Posted August 27, 2019 6 hours ago, andyscotland said: Very interested in this for the ensuite in my garage conversion. I won't have an MVHR, do you think it would be feasible to link it into the extract somehow? Planning to fit an inline ducted fan so I could possibly boss into that with some kind of flow restrictor? Or would that risk causing noise/other issues? I was wondering whether I could introduce a Y shaped junction in my (currently flexible) extractor ducting or whether if the room extractor was on it'd blow back into the cistern/pan? My main bathroom lighting is 4 down lights on a Quinetic dimmer system. Because of the dimmer module I've put the extractor fan on the separate feature, (blue) lighting circuit that's on a Quinetic switched receiver. In two minds whether to introduce an occupancy sensor for the lights/fan. The extractor fan is imo quite noisy and as I say comes on when the feature lighting is switched on. It also has a humidistat so it comes on at 65% humidity independent of the mood lighting being on. Tbh I think I'd rather just the pan fan came on as required. Was considering whether if I took the fresnel lens off an occupancy sensor and mounted it directly above the WC it'd just "look down" at someone sitting on the loo... Or just a bog standard, occupancy sensor without any mods that just triggers the pan fan when you walk in and consider what else the switch can be used for later? Still fancy a very short range/restricted beam angle jobbie. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 27, 2019 Author Share Posted August 27, 2019 I can't see why it wouldn't work just fine plumbed in to an extract fan. Just a matter of making up some sort of connection to the inlet side of the fan. 1 Link to comment Share on other sites More sharing options...
Onoff Posted August 27, 2019 Share Posted August 27, 2019 22 minutes ago, JSHarris said: I can't see why it wouldn't work just fine plumbed in to an extract fan. Just a matter of making up some sort of connection to the inlet side of the fan. This is my fan. Couldn't really introduce anything to the inlet side... Link to comment Share on other sites More sharing options...
andyscotland Posted August 27, 2019 Share Posted August 27, 2019 20 minutes ago, JSHarris said: I can't see why it wouldn't work just fine plumbed in to an extract fan. Just a matter of making up some sort of connection to the inlet side of the fan. Thanks. I'm planning to use rectangular duct and the fan itself is in the next door utility room so should be fairly easy to fashion some sort of connection into the duct before it goes through the wall. Will have a play about when I get to that point. Link to comment Share on other sites More sharing options...
dpmiller Posted August 27, 2019 Share Posted August 27, 2019 20 minutes ago, Onoff said: This is my fan. Couldn't really introduce anything to the inlet side... you could rig up a venturi in the extract duct to draw from the cistern feed. Link to comment Share on other sites More sharing options...
ToughButterCup Posted August 27, 2019 Share Posted August 27, 2019 25 minutes ago, dpmiller said: you could rig up a venturi in the extract duct to draw from the cistern feed. Setting up a choke (venturi?) in this context is errrmmm interesting. Forgive me, I'm bit of a Slow-Bear this morning Your idea fascinates me. How in an extract air duct might I create a venturi powered by the cistern (water ?) feed? Link to comment Share on other sites More sharing options...
dpmiller Posted August 27, 2019 Share Posted August 27, 2019 not powered by, Ian. Create a low pressure zone in the main extract duct to draw flow from the duct coming from the cistern. Link to comment Share on other sites More sharing options...
Onoff Posted August 27, 2019 Share Posted August 27, 2019 10 minutes ago, dpmiller said: not powered by, Ian. Create a low pressure zone in the main extract duct to draw flow from the duct coming from the cistern. You draw it and I'll make it! Link to comment Share on other sites More sharing options...
dpmiller Posted August 27, 2019 Share Posted August 27, 2019 might get away with nothing more than bringing the cistern duct into the main one with an elbow facing downstream. Link to comment Share on other sites More sharing options...
Onoff Posted August 27, 2019 Share Posted August 27, 2019 42 minutes ago, dpmiller said: might get away with nothing more than bringing the cistern duct into the main one with an elbow facing downstream. How to test? Just "sniff" or something more exotic like coloured smoke? Link to comment Share on other sites More sharing options...
dpmiller Posted August 27, 2019 Share Posted August 27, 2019 smoke stick / joss stick would do it Link to comment Share on other sites More sharing options...
Onoff Posted August 27, 2019 Share Posted August 27, 2019 59 minutes ago, dpmiller said: might get away with nothing more than bringing the cistern duct into the main one with an elbow facing downstream. I'll look to extend the nom 100dia hard, grey plastic section coming off the back of the fan, looks like it'll solvent weld. Thinking then a strap boss, 45deg elbow to the 32mm dia pipe? Flexible duct onto the 100dia extension. All needs to be demountable if ever I need to change the fan. This fan was only meant anyway as a stop gap before eventual MVHR. Link to comment Share on other sites More sharing options...
jack Posted August 27, 2019 Share Posted August 27, 2019 15 hours ago, Onoff said: I REALLY need to get my ar$e in gear and fit a fan to my unfinished pan take off system. My youngest has, on occasion, slid an A4 sheet under the door whilst I'm in there with the word "SMELLS!" scrawled with a Sharpie. Get back on the low-carb diet. 1 Link to comment Share on other sites More sharing options...
Onoff Posted September 1, 2019 Share Posted September 1, 2019 I've ordered a bit of 100mm pipe and a coupler: However...as it is the bathroom gets so humid when used as a wet room, the current extractor fan will run for a good few hours or more until it's below 65%. I've yet to check if I've an adequate gap under the door. If I connect the pan to the extractor won't I just be sucking warm air out of the room that way too...for hours? Link to comment Share on other sites More sharing options...
dpmiller Posted September 2, 2019 Share Posted September 2, 2019 only a small proprtion of the flow will manage to make it up the small pipe. 1 Link to comment Share on other sites More sharing options...
Onoff Posted September 2, 2019 Share Posted September 2, 2019 12 minutes ago, dpmiller said: only a small proprtion of the flow will manage to make it up the small pipe. I just hope it's enough! I'm blaming the prawns I ate last night. Link to comment Share on other sites More sharing options...
Onoff Posted September 7, 2019 Share Posted September 7, 2019 (edited) I bought a 100mm dia pipe and coupler to extend where the extractor comes up through the ceiling: The pipe coming up from the Geberit cistern into the loft is 32mm solvent weld so I've got a few extra fittings: The plan is/was to drill a 36mm OD hole in the side of the pipe then introduce an elbow, with a straight coupler the other side, linked with a short bit of pipe. I'd lay sandpaper on the 100 dia pipe and rub one end of the elbow and coupler on it to concave the faces. This to better mate to the big pipe. It'd put the 32mm pretty much dead centre of the 100mm pipe: Looking at it though this I think will severely impede the csa of the 100 dia pipe for it's primary purpose as a room extract, or will it? Edited September 7, 2019 by Onoff Link to comment Share on other sites More sharing options...
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