tumble dryer vent pipe length?

One of the to-do list tasks is to throw the tumble dryer down in the basement... does anyone know a typical limit for vent pipe length (and or number of turns)?
Obviously "short and straight as possible" is good, but I've got a few options as to where I'll put the vent on the outside wall above, some better than others (flowers / bushes in the way, and whatever I do* the pipework's going to be passing up through the kitchen floor behind the floor-level cupboards)
* unless dryer vents exist in long-and-thin profile, rather than the usual square? The basement ceiling sits at about 3" above ground level so there'd be space to fit something between the beams at ceiling height (I want to avoid a concrete trough such as around basement windows, which would just end up collecting water and filling up with dead leaves).
ta
Jules
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Jules coughed up some electrons that declared:

Could you not adapt the dryer to long and thin (aka rectangular) ducting, eg:
http://www.tlc-direct.co.uk/Main_Index/Ventilation_Index/Ducting_Flat_5/index.html
If you can adapt the tumble dryer to 4"/100mm round then there are adaptors for round to the above. If not, then there's duct tape :)
TLC don't have the full Manrose range - for example you can get 45 degree bends in either axis which may be useful.
HTH
Tim
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On Thu, 20 Aug 2009 21:54:10 +0100, Tim S wrote:

Yep! I'd not really thought of using it in a non-heating context (I was going to find some plastic pipe for the dryer), but I don't see why the galvansied stuff shouldn't do the job. As I'm in the US, there's *heaps* of ducting of all sorts of configurations on the shelves at the DIY sheds (actually I've even got a round to 12x2" rectangular section sitting in the spares pile, although I don't remember what diameter it is now; I think the dryer's 4")
What I'd be lacking though is a rectangular vent to go on the outside wall - one of the plastic ones with slats which open up when there's airflow, but which stop crap and critters getting in otherwise. I think I've only ever seen ones for dryers (or cooker fume extraction etc.) in square profile, not rectangular... I'll have a poke around at the local DIY places, though.

:-) If it needs taking apart, use an angle grinder. If it needs putting together, use duct tape...
cheers
Jules
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Jules wrote:

Unless I'm misunderstanding the situation, why does it have to be rectangular where it goes through the wall?
My tumble drier sits in a corner and has 5" rectangular ducting which conducts vapour from the base of the machine to a hole in the side wall, which requires IIRC four 90-degree bends and about 5' total length wrapped around the machine - works fine. The hole in the wall is round, and the ducting connects to it with something like this:
http://www.screwfix.com/prods/96549/Heating-Cooling/Ducting/Manrose-Elbow-90-Bend-100mm
Even if you want to go through the wall with rectangular ducting (which may be advantageous), there's nothing to stop you covering the hole on the outside wall with a square vent, anyway.
David
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On Fri, 21 Aug 2009 07:56:46 +0100, Lobster wrote:

Well the underside of the ground floor (i.e. the floorboards, which also form the ceiling of the basement below) sit above ground level by only about 3", so if I drill right at ceiling height in the basement through to the outside, I'll only have about 3" of vertical space - but the joists in the basement (supporting the floor above) are on 16" spacing, so there's quite a bit of horizontal space between them to accomodate a wide vent.
(It's actually more like 4" of height I've got to work with, but I don't want the exterior vent sitting flush against the grass, and the standard square vents seem to be 4" x 4")

That's useful. I think to get it through the wall at ceiling height in the basement I'm looking at two 90-degree bends, a vertical run of about 7' and horizontal of 4'.
To just run it up via the kitchen (hidden by cupboards) would be maybe 8' and again two 90-degree bends - which is shorter, but running it via another room does feel like a bodge, even if nobody would ever see it!
Unfortunately I can't get the dryer closer to where I'd want to vent it via the top of the basement wall, as the well pump and pressure tank are in the way - and relocating those is asking for trouble :-)
I could raise the dryer up so it's not at floor level in the basement, I suppose - after all, it's less convenient that way anyway. But I'm not sure if saving 3' (or so) on the vertical would be 'enough' to go out via the basement wall (although it sounds like it could be for the bodgey kitchen route).

It's just a clearance issue on the outside - and I think anything other than having the vent cover flush with the outside wall would just look messy.
My experience of 'pits' on the outside for things like basement windows is that they tend to fill up with debris and make for great moisture traps, so I'm reluctant to go that route if I can help it.
Maybe I need to source some suitable pipe and just do some tests (although that would best be done when outside air is coldest, I suppose, but then I don't think the basement gets much lower than about 45F in Winter - so if I pick a cold night in the coming weeks...)
cheers
Jules
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Jules wrote:

Have a look here - they sell all sorts of ducting and transitions from rectangular to round, in a number of sizes. The 3-1/4" x 10" size might do you.

When we installed a dryer in our basement, it was placed on a platform for two reasons - one, to keep it away from possible flooding, and two, to make it easier to load and unload. If you install a big drawer in the platform, it can keep laundry supplies neatly contained.
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On Fri, 21 Aug 2009 09:36:08 -0400, S Viemeister wrote:

That's an excellent idea. There was me pondering on what the heck to use the 'wasted space' for if I did go that route. :-)
J.
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replying to Jules, KPLLOYD wrote:

The Platform/deck out of pressure treated materials is a excellent way to protect your basement utilities Water heaters / pressure tanks/ well pumps/ Etc. Put your boiler on platform then place termite blocks on it , Your platform idea is great insurance for each home appliance in damp basements KP
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You can get the same effect if you use a stacking kit to put the dryer atop the washer, assuming the appliances are stackable.
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On Fri, 21 Aug 2009 11:36:06 -0700, gunsmith wrote:

It's all top-loaders this side of the Pond, unfortunately. USians are just discovering front-loaders, but sales volumes are still low, so as a consequence they come with a quite alarming price-tag :-)
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On Fri, 21 Aug 2009 07:54:28 -0500, Jules wrote:

OK, just been doing some measuring, and I think I have a solution...
As the basement walls are around 8" thick, I think I can cut through at a 45 degree angle rather than horizontal, which gains me quite a bit of height where the vent pipe will exit through the outside wall.
Doing it that way should allow the vent to sit high enough up above ground outside, still allow me to use a square vent, and allow me to vent out via the wall directly behind the dryer in the basement space, rather than a longer run to a different wall or up through the kitchen.
Total run will probably still be about 5' with the dryer on a platform, but that seems short enough that I'm willing to chance it (it has no problems with the current 3" run via flex-duct, anyway). The only issue is whether the exhaust from the dryer is going to cause problems in hitting the vent at 45 degrees rather than head-on, so I'll rig up some sort of test there with the existing vent cover and see...
cheers
Jules
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<snip>
The vents I have seen with flaps have needed a reasonable breeze to overcome the spring and make the flap open.
Will you get enough pressure over a long run to make the flaps open?
[Ignoring, of course, the condensation issues raised elsewhere.]
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On Fri, 21 Aug 2009 11:16:55 +0100, David WE Roberts wrote:

Yes, that was partly my original question, I suppose - not only must there be some maximum length / number of turns beyond which the dryer becomes useless, but it does need a reasonable flow just to get the louvers on the vent cover to open.
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I'm not sure if a condensing kit would work? Might be worth a try in order to avoid running pipe though a floor. Copy and paste this link for an idea:
http://www.toolstation.com/shop/Electrical/Ducting/Tumble+Dryer+Condensing+Kit/d190/sd3083/p65417
Some other people on here may have experience of such units.
Tom
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Jules submitted this idea :

Might you not find that the moisture condenses in the pipe and simply runs back down?
Might it not be better to try to condense it deliberately and into a drain, rather than venting it? All you need to do is create a large cold surface area for the moist air to pass over.
--
Regards,
Harry (M1BYT) (L)
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On Fri, 21 Aug 2009 00:34:49 +0100, Harry Bloomfield wrote:

Hmm, now that's a really good point. Maybe I'll see if I can find a good US equivalent to uk.d-i-y as lots of folk here have dryers in the basement, so there must be a common way of handling it (may be that everyone uses a condenser as Tom mentions!)

Quite possibly; if I get the washing machine down into the basement (as mentioned in another thread) the I can use the same holding tank that the washing machine drains into to receive any liquid from the dryer.
cheers
Jules
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I can confirm that an extended hose on a drier becomes a very effective condenser. When we had to locate our dryer temporarily in our garage, I had a double length of hose on it and it worked fine for a while but then appeared to be blocked. On closer inspection a hanging loop was completely full of water.
I guess this could be reduced by insulating your duct or perhaps you could think about deliberatly introducing a "U" tube type hanging loop with a drain to capture the condensate and prevent it flowing back to the dryer?
TIm
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wrote:

IIRC the manual for my Miele dryer has a formula for calculating the effective duct length etc, might be useful.
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