Tumble dryer condensor box in loft

My brother recently asked me to take a look at his bathroom ventilation as it didn't seem to be working very well.
He has 2 light/vents fitted above the shower which are each attached to in- line fans. The output of the fans are then joined together using a Y piece connector which is then connected to a tumble dryer condenser box.
Connecting the output to a tumble dryer box doesn't strike me as a good ide a. Am I right or is it normal practise?
The actual problem was one of the in-line fans not working very well. I re placed this (and its associated light/vent fitting which he broker when try ing to change the bulb) and suction improved.
I also noticed that suction was further improved when the flexible hoses we re not connected together via the Y piece. I assume that there was a degre e of "conflict" with the air flow and that if 2 vents need to be connected, it would be better to have a single fan positioned after the Y connecter p ulling air through rather than 2 fans before it, pushing air through?
Thanks
Alan
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On Sun, 5 Jun 2016 12:33:15 -0700 (PDT), AlanC

Why on earth has he got a condenser box on the end of his vent pipe? Is he attempting to recover heat or the water for some purpose (not a serious question BTW). Just let the extracted air exhaust to the outside. Our shower-room/toilet (probably smaller than your BIL's bathroom) has a single ventilation fan, is fitted with a one-way flap valve and vents directly outside.
As to the fans working better if not joined at the Y piece, this is presumably because you have two airflows being compressed into a single pipe, so there'll be a bit of back pressure (think motorway roadworks and tailbacks). Using a larger pipe beyond the Y should solve that problem.
--

Chris

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On 6/5/2016 9:11 PM, Chris Hogg wrote:

Presumably to avoid having to find a way to take the duct outside? Mine goes out just under the tiles, I might have had to remove a bit of soffit.
Agree with your analysis on flow. As OP says, single fan after Y might be better.
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At a guess, he's had condensation problems in the pipe due to either too long a run of pipe or too little insulation. Adding a condensation trap isn't the right answer though!
I had a similar problem when I temporarily had to put a dryer in a garage with a double length of hose. It was amazing how much water collected!
Tim
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wrote:

Yes, I can imagine from a tumble dryer you'd get a lot of condensation, but this is a bathroom. If condensation is really a problem, the OP's brother's family must have a lot of hot steamy showers! I would have thought the trap should be at the beginning of the pipe run, as near to the fans as possible, not at the end.
I'm assuming his system vents to the outside. But I suppose it may only vent into the roof space, in which case a trap would be almost essential otherwise he'd get condensation there, resulting in damp, mould and possibly rot of the roof timbers, eventually.
--

Chris

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Yes this does sound like some crazy idea to me.
I'd also be a bit wary of all the moisture in the loft leading to some nasties like mould etc. Brian
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On Mon, 6 Jun 2016 09:43:32 +0100, Brian Gaff wrote:

Presumably the tumble dryer box (not a condensation trap, that's something different) is some ones half thought through idea of not dumping the warm damp air from the bathroom into the loft. Air goes through box dampnes collects in box not in loft. But what then happens to that water? Is there a drain from the box or does it just evaporate into the loft...
Be much better to vent each fan individually outside, either via soffit or tile/ridge vents.
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Dave.
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I spoke to my brother again, to get a bit more background info.
He paid a builder to install this ventilation about 3 years ago. The build er said that this solution would be fine and that any water that collects i n the tumble dryer box would evaporate. My brother confirms that he has ne ver emptied the box in that time and he has never noticed any water in it w hen he has been up there.
I think the builder did it because it would require a long vent pipe run to get to the external wall (about 6 meters). The house is semi detached so one direction is a no-no. The bathroom is at the front of the house (on th e neighbor side). The roof is a single pitched roof but there doesnt seem to be any access out via soffits (doesnt have any soffits).
Looks like the best course would be to exit via a vented roof tile (as sugg ested). Second best would be a long rigid vent pipe run to the external wa ll with a suitably powerful fan.
It did strike me as being a bit of a bodge but I thought I would double che ck in case its a standard thing. From everyone's responses its not a stand ard thing!
Thanks all.
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