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In a previous thread I noted that I am having my first bout with rust in my layout after 15 years in place in my basement. I got a humidifier meter which registers the humidity between 50 and 57%. What should I look for in a mechanical dehumidifier for a basement that is approximately 10 ft by 20 ft?

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I don't know where you live, but here in NJ this past summer we had August like heat and humidity from june on and I ended up with rust (in large part because I trusted a standalone AC to handle the humidity, it didn't...). Anything below grade generally has humidity problems IME.

I agree with GRJ, with that small a basement (is 10x20 the full size?) a 40 pint would likely work fine. The other question I have is your basement finished or open walls? If it is relatively unfinished, I would go with a larger model, like 60 or 70 pint (or whatever they are offering these days). If you have a sump pump or any kind of drain, I would feed the output of the dehumidifier into that, having to dump it is a pain. I do what GRJ does, I have my unit set to 40% and the air in the basement is good now. Now I just have to work on the rust......I grew up in the house I live in now, the basement wasn't finished back then, didn't even have a french drain system,never had a dehumidifier, and my track never rusted.Back then we may have had a couple of weeks of high temperature/high humidity in August and occassionally otherwise, now it is is like the entire summer.

Go to Home Depot, buy a 70 pint unit that has the ability to add a drain hose (so it can be set up to continuously drain). Then buy the service plan when you check out. They don’t last, use of the $40 plan is a guarantee and they’ll just refund you to go buy another one.  

This is great advice, but I'll go you one better. Buy the 70 pint at CostCo... they will take it back anytime for a full refund w/o any service plan malarkey.  Just keep the paperwork.  They always fail, and they've replaced mine 3 times now over the course of many years.

Like John, I keep it at about 45%, the 70 pint covers the 1200 sq/ft area(Drylocked/treated).  It's plumbed directly into the drain.

Last edited by ADCX Rob
@ADCX Rob posted:

This is great advice, but I'll go you one better. Buy the 70 pint at CostCo... they will take it back anytime for a full refund w/o any service plan malarkey.  Just keep the paperwork.  They always fail, and they've replaced mine 3 times now over the course of many years.

Like John, I keep it at about 45%, the 70 pint covers the 1200 sq/ft area(Drylocked/treated).  It's plumbed directly into the drain.

The op has a 200 sq ft basement. A 70 pint dehumidifier is way overkill not to mention the extra cost ,and noise it will make.

I think a smaller more affordable 15 pint would be more than adequate. I certainly wouldn't go bigger than 30 pints.

Last edited by RickO

Both of mine are piped to drains, one is next to my sump pump, the other I drain in the floating basement channel in my back workroom.  I highly recommend NOT counting in emptying the bucket all the time, that's a recipe for forgetting and having the humidity shoot up when the unit is no longer running.

It's good exercise to empty the bucket once or twice a day, especially after sitting around running trains.😉 That's what I do.

If you do use the drain hose feature. I recommend flushing it with vinegar periodically to keep it from clogging with algae over time which will back up the unit and cause it to ice up.

Last edited by RickO

Actually, it really depends on the characteristics of the basement.  I doubt the $50 difference in price between a larger dehumidifier and a tiny one will be much of a burden, and he could well find the smaller unit really isn't up to the task!

It's actually hard to find a 70 pint model nowadays, the new ratings in 2020 made them all into 50 pint units.  I've been in small basements where a full sized 70 pint unit had it's hands full keeping up with the moisture, so I'd be loath to recommend a tiny unit.

@RickO posted:

It's good exercise to empty the bucket once or twice a day, especially after sitting around running trains.😉 That's what I do.

If you need that exercise, then by all means, that's what you should do.

@RickO posted:

If you do use the drain hose feature. I recommend flushing it with vinegar periodically to keep it from clogging with algae over time which will back up the unit and cause it to ice up.

You do have to do this occasionally, I find once a year is sufficient when I service my humidifier for the furnace.  In any case, any unit I've had doesn't ice up if the hose stops draining, it simply fills the bucket and turns off.  The hose for the drain connects in place of a cap that is used when you are using the internal bucket, there is no risk of overflow or icing if the hose gets plugged.

Both of mine are piped to drains, one is next to my sump pump, the other I drain in the floating basement channel in my back workroom.  I highly recommend NOT counting in emptying the bucket all the time, that's a recipe for forgetting and having the humidity shoot up when the unit is no longer running.

I also have two units running so that I still have one in service in the event of the inevitable failure.

@ADCX Rob posted:

This is great advice, but I'll go you one better. Buy the 70 pint at CostCo... they will take it back anytime for a full refund w/o any service plan malarkey.  Just keep the paperwork.  They always fail, and they've replaced mine 3 times now over the course of many years.

Like John, I keep it at about 45%, the 70 pint covers the 1200 sq/ft area(Drylocked/treated).  It's plumbed directly into the drain.

Good advice except that Costco sells them seasonal as in spring to early summer. When they are gone, thats it for the year.

It is still amazing me that people are recommending small dehumidifiers without knowing anything other than the size of the basement.  I've been in small basements that would take a ton of capacity to properly dehumidify, you really have to know the environment before sizing the unit.

Just going on what been stated, doesn't seem like he has a overly wet basement.  Of course there's special situations that would change what he may need.

Last edited by superwarp1

In terms of power usage the draw on a dehumidifier is when the compressor is kicked in. A small unit that runs the compressor continuously to keep up with the space will likely draw as much power as a bigger unit that cycles from fan only to compress to off. Yes, there is a surge of draw when the compressor kicks in, but in the long run having a larger unit won't cost you more in power usage. The other thing is what GRJ said, a 30 pint might work fine most of the time, but if there is a really humid summer or really rainy weather where below grade is subject to more moisture, the larger capacity unit will handle it. 

There is an alternative to a dehumidifier , especially in a small basement, you can have an exhaust fan controlled by a humidistat. When the fan is running (it is obviously vented outside), it creates negative pressure in the basement and it can bring air down from higher up in the house, where it is likely a lot more dry. When people do this they usually have a vent that allows air to move from the first floor down to the basement. This is basically what commercial systems like "the wave system" do at a ridiculous price. There are downsides, if there is a gas hot water heater in the basement the negative pressure can draw exhaust gas from the hot water heater depending on how much of a negative pressure there is, and obviously you can be venting cooled air/heated air out (I generally don't have to use my dehumidifier in the winter FWIW).

Humidity is a pretty hard thing to control in an unsealed area. Even in my relatively new home (circa ~2000) that has a poured concrete foundation, the humidifiers run A LOT more after it rains. We've never had water in our basement, and have never had trouble with crazy high humidity - though this basement is part of the air conditioned space.

Until you run a dehumidifier for a while you won't really know how "porous" your basement is. The same goes for the "wetness" of the surrounding earth, since we're really fighting the rate of osmosis when it boils down to it.

This is all basically to say that there's literally no way to predict what size of dehumidifier you'll need. Personally, I would start small/cheap and see if it works knowing that you may need a second one or a bigger one.

I don't run the dehumidifiers in the true winter months, but they just sit with a 40% setting, but since humidity never gets that high, they never run.

Same here in NC, ….seems like my machine runs sometimes in the height of summer when the humidity climbs, but almost never in the fall & winter,…..mine sits at 40% …..seems just dry enough to accelerate traction tire dry rot,….😉

Pat

@rplst8 posted:

Humidity is a pretty hard thing to control in an unsealed area. Even in my relatively new home (circa ~2000) that has a poured concrete foundation, the humidifiers run A LOT more after it rains. We've never had water in our basement, and have never had trouble with crazy high humidity - though this basement is part of the air conditioned space.

Until you run a dehumidifier for a while you won't really know how "porous" your basement is. The same goes for the "wetness" of the surrounding earth, since we're really fighting the rate of osmosis when it boils down to it.

This is all basically to say that there's literally no way to predict what size of dehumidifier you'll need. Personally, I would start small/cheap and see if it works knowing that you may need a second one or a bigger one.

Exactly.  I started out with one 70 pint (with the new standards it's a 50 pint) unit, and it wasn't quite enough, especially on the humid spells where the temperature and humidity outside were high. This is a basement that has never had water, is all finished except for the small back room, and is a walk-out as well.

I have deliberately removed my basement from the main heat and A/C because being a different level and having different thermal characteristics, that was a poor fit.  I added a ductless split heat pump on my wall, I have independent temperature control.  Even when it's hot and humid outside, the basement doesn't rise above the middle 70's, so trying to modulate the the A/C for the upper floor and the basement was a constant balancing act.  That being the case, I rarely use the A/C feature of the ductless unit, it mostly gets used to bring the basement from the low 60's up to 70 in the winter.

The price difference between a 20-30 pint unit and a 50 pint unit is peanuts, this was a no-brainer to me.  Buy the larger capacity and you won't have to regret buying the small one.

Do you really want to fool around with buying the lesser model and finding out it doesn't do the job for $30-40 extra for the higher capacity?

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@RickO posted:

It's good exercise to empty the bucket once or twice a day, especially after sitting around running trains.😉 That's what I do.

If you do use the drain hose feature. I recommend flushing it with vinegar periodically to keep it from clogging with algae over time which will back up the unit and cause it to ice up.

Not to mention that it is a good source of providing some water to your trees, plants and vegetation in the spring and summer when outdoor water usage may be banned in drought-ridden areas, rather than just emptying it down the sink drain.

In the metro Boston area for the past few summers, and especially this summer, many towns which rely on local water supplies instituted restricted or total outdoor water bans, with violators receiving a citation and fine. In some situations, it has pitted neighbor against neighbor and led to 2:00 AM patrols and listening for the tell-tale sound of water sprinklers operating in the middle of the night.

My town went from two days a week to a total ban over the summer and has banned the digging of new private irrigation wells since they draw from the same underground source as the town supply.

Even those communities served by regional water supplies like the Massachusetts Water Resources Authority or the Quabbin Reservoir requested voluntary restrictions. 

Being able to empty my humidifier bucket to provide water to my drought-sensitive trees and plants on a daily basis at least provided some relief.

My train space is an unused 2-car (heated) bay of our large garage barn.  I acquired a Toshiba dehumidifier last spring, set it to "comfort", and it maintained 50sih percent humidity in the train space all summer.  No rust visible on track or anything else, this fall.  Hosed into a floor drain, it seemed to work well.

I too have gone to Home Depot and bought a 70 pint LG brand dehumidifier. My thinking is the higher the humidity the more you can extract in a 24 hour rating puts less stress on the unit. I keep mine set at 40-45% and things feel great.

Wisconsin winters are tough temp wise so the furnace does the drying out.

One thing I have to do is always try to turn off the unit during thunderstorms which could cause a brown out. Seems that is when I have to toss a unit out and buy another as the compressor seems to be shot.

That's my two cents worth.

My train room in my basement is 36’ x 24’. Over the past 27 years I was replacing store bought dehumidifiers every 3 years. 3 years ago I bought a commercial unit and have never had any issues. When we Built the house I had a drain put into train room wall that is tied into the town system. Dehumidifier is piped into it. I have humidity set at 54% & have no issues. Very comfortable.

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Last edited by Captain John

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