MVHR - no water trap condensate drain - what is it?

[readiescards]

What is this thing doing that a water trap does not?

http://www.fantronix.com/acatalog/Heat-Recovery-System-Condensation-Drain-Kit.html

 

Thanks

[Jeremy Harris]

You can't be sure that a water trap will stay wet with MVHR, as for several months of the year there won't be any condensate to keep it full of water.  I fed mine to a drain that also takes the waste water from the softener, so I know that the trap will always have water in it.

[PeterW]

It's only a posh looking HepV0 trap which you can get for £20 or less if you look on eBay. 

[lizzie]

Reviving this thread as looking for some help please.

 

I seem to be getting drain smells around the house......found one source under the kitchen sink where the rubber cover over the big pipe going into the ground was not properly sealed and letting smells out.  Seealed that a week ago and smells less obvious but still evident ow and then. My office is a small room and often has a faint aroma of drains.  I am noticing it in our TV snug room too. The bigger open plan spaces dont seem to be getting it but it may be that it just disperses in the bigger space.

 

I think it may be coming via MVHR as I cant see how else it would be occuring.  The unit makes a lot of gurgling and glugging noises and often sounds like there is water sloshing around inside.  The condensate trap seems to dry out quickly and I have to put water in...and its really difficult as its a u bend under the unit with not much clearance between unit and floor to get under it.

 

We are getting headaches and sore throats in certain rooms in the evenings, I have been opening windows in the day so problem not occuring then. I have now turned off mvhr to try and see if that helps.

 

Any ideas? Should I get MVHR engineer out?  

 

thanks for  any pointers you can give me.

 

 

[ProDave]

sagging loops in the duct runs? condensation forming in the sags? nasty bugs and smells breeding in the stagnant smelly water?

[lizzie]

2 minutes ago, ProDave said:

sagging loops in the duct runs? condensation forming in the sags? nasty bugs and smells breeding in the stagnant smelly water?

Oh please no......it was my huge fear about having mvhr. I spent eons of time looking at this. I have a lung condition and the air quality is very important, bugs could kill me.

 

The ducts/pipes are totally inacessible up in the roof, we do not have any accessible roof space (flat roof) there is no way to get at anything other than taking down ceilings and the huge amount of pumped insulation above the vapour barrier.

 

Any idea how I can find out if its in the inaccessible ducts?

[PeterW]

Disconnect the duct at the Unit end and pull a piece of wool through from the room with a Hoover. Now pull decent string through and tie a rag or J-cloth onto the string and pull it though the duct. 

 

You will see from the cloth if there are any issues. 

[lizzie]

@PeterW I will have to get someone in to help me do that pipes are now all neatly boxed in where they go through the ceiling, will have to get all that ply boxing off.........I dont recall any labels saying which pipe was which but guess there must be some sort of label somewhere. Thank you.

[Jeremy Harris]

TBH, I doubt very much that it's anything to do with the ducts at all.  The air flowing through the room supply ducts will keep them dry, as long as they are inside the insulated envelope or are well insulated, and at this time of the year there's practically zero chance of getting condensation in the ducts, anyway.

 

It's far more likely to be a problem with a trap somewhere, and the MVHR is then drawing in smells from the drains.  I didn't trust the suggested arrangement for the MVHR trap in the instructions for ours, so I raised the MVHR up on a stand, to get better clearance underneath it (also allowed me to fit anti-vibration mounts) and plumbed the drains to a normal 32mm U bend trap.  I also plumbed the water softener drain to the same trap, which makes sure it stays topped up. 

 

The mention of gurgling noises suggests that air is being pulled up past the MVHR drain trap arrangement, and I'm near-100% certain that your problem will be with that being too shallow, or perhaps with water being sat in the drain tray in the MVHR because it's not angled properly towards the outlet.

[lizzie]

@JSHarris that makes a lot of sense thank you.  I think I need the installer back. 

 

I had no smells overnight with the mvhr turned off and windows open on tilt for ventilation so thats ok as a temp measure

[JanetE]

We have one of these fitted to our MVHR and absolutely no problems. As you can see it can be fitted horizontally or vertically.

https://www.screwfix.com/p/osma-waste-valve-white-x/1819k

[lizzie]

28 minutes ago, JanetE said:

We have one of these fitted to our MVHR and absolutely no problems. As you can see it can be fitted horizontally or vertically.

https://www.screwfix.com/p/osma-waste-valve-white-x/1819k

Thank you.  I am no plumber and cant immediately see how I would fix this to my waste....will have to ask a plumber I think unless anyone can advise....

 

this is my current waste its just a ubend and there is a little plastic ball in there, seems to float.

 

. 

[ProDave]

Is this trap just serving the mvhr condensate ?

 

If so it's probably nothing more than the water in it has evaporated.  Just pour a jug of water down it from inside the mvhr unit and try it again.

[lizzie]

32 minutes ago, ProDave said:

Is this trap just serving the mvhr condensate ?

 

If so it's probably nothing more than the water in it has evaporated.  Just pour a jug of water down it from inside the mvhr unit and try it again.

It is just the MVHR trap.  I have been taking the ubend bit off and filling it with water and then screwing it back on, not easy doing that in the small space under the unit..... there is no where obvious on the mvhr unit to pour water would I have to unscrew the front cover?  Sorry I'm really thick with these things LOL

[Nickfromwales]

Just change it to a "waterless" trap and have done with it. 

Anythihg like the hepvo traps. 

 

[Jeremy Harris]

I'm inclined to think that there may be an issue with the angle that the MVHR is fitted at, and that perhaps the drain tray isn't allowing condensate to flow easily to the drain hole.

 

It should be pretty easy to check if the MHVR has been mounted dead level, some are quite critical of being mounted level as the angle on the drain tray often isn't very great.

 

For the longer term, once it's been levelled properly, then I'd go along with the suggestions by @JanetE and @Nickfromwales and fit a waterless trap, but before doing that I'd want to be absolutely certain that you don't have condensate pooling in the drain tray inside the unit.

[lizzie]

Thank you all I'm off to find the spirit level!