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dehumidifier drain to outside? Or distant indoor drain?

Posted by jally (My Page) on
Sun, Apr 29, 12 at 16:12

A home repair guy is due to come very soon to install two dehumidifiers in my basement, but leaving the decision up to me whether to hook up the drain hoses to the laundry tub drain which is a long convoluted distance away, or:

...or alternatively:
drill holes approx. 6 1/2 feet up the wall into the thick cinderblock, providing a much more direct outlet for the hoses to drain outdoors into the window wells (which would be filled with gravel).

Either way, the dehumidifiers would be placed on specially-built high shelves, enabling efficient drainage gravity.

My main concerns is whether the hoses might freeze outdoors, in the event I forget to shut the dehumidifiers during cold weather.

If there's anyone experienced in such matters, i'd appreciate any feedback you can offer.

Follow-Up Postings:

RE: dehumidifier drain to outside? Or distant indoor drain?

P.S. Does this post belong more on one of the below forums & if so which? It's confusing.


RE: dehumidifier drain to outside? Or distant indoor drain?

I am a plumber so I will offer you the same answer here as I would in the plumbing forum....LOL

Your installer is correct, the discharge line from a dehumidifier is required to discharge outside the structure or into the house DWV (drain, waste & vent) system by means of an approved indirect waste connection.

To make an approved "indirect waste connection" the discharge end of the hose may terminate into a utility sink, floor drain or sump pump pit, but when doing so, the termination point of the discharge line must remain a minimum of 2" above the flood level rim of the receptor.

The simplest method to make a code approved discharge point would be to drill a hole through the wall and extend the line outdoors as suggested, however whe doing so, the discharge end of the line must be a minimum of 6" above the average finished grade below the discharge line.

Generally there is not much concern about frost closure on the line because in the coldest part of winter when freezing would be a problem the ambient humidity is well below the operating parameters of the dehumidifier so we would expect a minimum amount of water discharging from this line; assuming of course that your laundry dryer and showers are adequately vented to the outside as well.

If you do have concerns about freezing there is a method to minimize that. Typically the discharge line from a dehumidifier is a small 3/8" plastic tube. You could install a 1/2" or 3/4" copper or PVC pipe through the wall at a steep angle of say 20 to 45deg downward from just inside the wall to the termination point outside, then stub up a 3 or 4" section of the copper or PVC vertical inside the house and put the end of the dehumidifier line into the vertical stub. With the 3/8" line just stubbed into the 1/2" or 3/4" vertical stub that will allow air to vent into the pipe, thus insuring a rapid velocity of flow as it passes through the wall thus minimizing any ice buildup on the outside end of the line.

My concern would be in putting the line into a window well. During the rainy season in spring & fall your dehumidifiers may generate 3 to 5 gallon of water per day. It would depend your local soil conditions and what type of drainage they have for your window wells. If there is no adequate drainage I could see your window wells rapidly looking like aquariums when viewed through the basement windows.

RE: dehumidifier drain to outside? Or distant indoor drain?

You can utilize condensate pumps, if necessary.

RE: dehumidifier drain to outside? Or distant indoor drain?

Thanks! That part about window wells becoming aquariums decided me on choosing the indoor option, however much a length of piping it would require.

This way, I can more readily see what's draining (and how effective the dehumidifiers are), by asking him to drain the pipes into containers placed inside the laundry tub, to see how full the containers get.

Not to mention creepy crawlies which could get into the pipes if drained outdoors.

Also not wanting to risk voiding any service contracts which they might do if the drainage is outdoors.

While i couldn't sometimes grasp your technical wording, note that the basement ceilings are 7' high & there's only 21" from the window-frame Upper that's nearly flush with the ceiling, until the window-sill which appears to be flush with the base of outdoor window wells.

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