Dehumidifier?

[Bill O]

Originally Posted by tkeithlu

Here's the small one ($50) we use. I rigged it with a 15/64" hole in a lower corner of the small tank, pushed a 1/4" hose though the hole, set it on the counter by a sink, and let it drain into the sink. I'm running this one on 12vDC although its 120vAC power supply produces 9vDC. It doesn't seem to mind.

https://www.amazon.com/Pro-Breeze-El...s%2C519&sr=8-4

Interesting, had never seen/looked for something that small.
The small size is nice, but really wondering how useful it is if it can only remove up to ~ 1 cup of water/day in the main cabin. Something like this could be good for a closet w/poor air circulation.

Bill O.

[Group9]

We live in a high humidity area, and we have always run a dehumidifier on our cabin boats when in the slip. The only times we have ever had mold and/or mildew, was when we didn't.

We just run the drains to the bilge.

[tkeithlu]

Actually, the little dehumidifier does the whole boat. The key is that it's closed up when the dehumidifier is running, so, I guess, no more moist air than it can handle gets in per day. I've never measured either the humidity of the amount produced, but it stopped persistant mildew in the two heads and around the bedding. An identical one does two bedrooms and a bath in our house, again under the premise that everything is closed up.

[Waterford]

Originally Posted by GreenWave

What kind of unit do you have? Details, price, source?

The front says FRIGIDIAIRE. I think I got it at Lowes but I see Amazon has it too.

[Cpt Pat]

Dehumidifiers have two problems: 1) you have to seal up the boat for them to be effective - which encourages mold. 2) Where do you put the extracted water if you aren't there to empty a tank?


If you are in a cool climate, you can use a heater and a dehumidistat. I use a Honeywell H46C1166 dehumidistat and a convection oil-filled heater. CAUTION: I advise against any heater that has a blower fan. If the fan fails, the heater can melt down and start a fire.

You can see the operation of this setup in my boat's telemetry here: https://aprs.fi/weather/a/N8QH-9?range=week

The sawtooth pattern on the temperature and humidity charts is the heater being switched on and off.

Using a heater without a dehumidistat wastes energy -- with the dehumidistat, the heater operation can follow the ambient temperature up and down, using only as much power as needed to keep the relative humidity below your maximum setting. On cool, dry days, it doesn't operate at all.

[Woodland Hills]

How does a closed up boat with low humidity encourage mold? If the dehumidifier is working and the boat is closed up than the humidity is low, isn’t that the whole point of a dehumidifier?
It isn’t rocket science to run a hose from the fitting on the unit to a sump, bilge or sink.

[Cpt Pat]

If every area of the boat is bone dry, like summer in Arizona, closing up the boat isn't a problem. But it's very difficult to eliminate areas of local dampness without ventilation. Here's what the Army says: https://www.army.mil/article/219276/ventilation_eliminating_moisture_keys_to_stopping_ mold_in_its_tracks

Then there's the accumulation of airborne mold spores that have nowhere else to go seeding every square millimeter inside your boat.

If you are draining the humidifier into the bilge, doesn't that water just re-evaporate back into the cabin? Yes, the bilge pump can remove some of it, but I've yet to find a bilge pump that removes every drop. Maybe I'm missing something here, but removing water from the air only to put it in the bilge sounds to me like the curse of Sisyphus - where he had to roll a bolder forever up a hill - only to watch it roll back down. Vapor to liquid, liquid to vapor, ad infinitum.

[Group9]

Originally Posted by Cpt Pat

If every area of the boat is bone dry, like summer in Arizona, closing up the boat isn't a problem. But it's very difficult to eliminate areas of local dampness without ventilation. Here's what the Army says: https://www.army.mil/article/219276/ventilation_eliminating_moisture_keys_to_stopping_ mold_in_its_tracks

Then there's the accumulation of airborne mold spores that have nowhere else to go seeding every square millimeter inside your boat.

If you are draining the humidifier into the bilge, doesn't that water just re-evaporate back into the cabin? Yes, the bilge pump can remove some of it, but I've yet to find a bilge pump that removes every drop. Maybe I'm missing something here, but removing water from the air only to put it in the bilge sounds to me like the curse of Sisyphus - where he had to roll a bolder forever up a hill - only to watch it roll back down. Vapor to liquid, liquid to vapor, ad infinitum.

There may well be a more efficient way to do it.

All I know is, that having a humidifier running, and draining into the bilge, for the pump to move overboard, keeps us from having any mold or mildew. When we don't run the humidifier, and let it go into the bilge, we do.

[Woodland Hills]

Originally Posted by Cpt Pat

If every area of the boat is bone dry, like summer in Arizona, closing up the boat isn't a problem. But it's very difficult to eliminate areas of local dampness without ventilation. Here's what the Army says: https://www.army.mil/article/219276/ventilation_eliminating_moisture_keys_to_stopping_ mold_in_its_tracks

Then there's the accumulation of airborne mold spores that have nowhere else to go seeding every square millimeter inside your boat.

If you are draining the humidifier into the bilge, doesn't that water just re-evaporate back into the cabin? Yes, the bilge pump can remove some of it, but I've yet to find a bilge pump that removes every drop. Maybe I'm missing something here, but removing water from the air only to put it in the bilge sounds to me like the curse of Sisyphus - where he had to roll a bolder forever up a hill - only to watch it roll back down. Vapor to liquid, liquid to vapor, ad infinitum.

So what? As long as there is electricity the boat will have low inside humidity. Are you thinking I’m pedaling a bicycle generator to make power? The fridge and freezer need to be kept cold whether we are at anchor or at the dock, the lights and pumps need to be energized at all times, etc. the added draw of a couple 30pt dehumidifiers is negligible.
BTW, we drain ours into the shower sumps of which we have three that are always wet with the discharge from the a/c and sinks. Again the added water from a couple of dehumidifiers is negligible. You are making the assumption that without a dehumidifier draining into a bilge, that bilge would be bone dry: that is most likely incorrect for many if not most boats.

[Cpt Pat]

Originally Posted by Woodland Hills

So what? As long as there is electricity the boat will have low inside humidity. Are you thinking I’m pedaling a bicycle generator to make power? The fridge and freezer need to be kept cold whether we are at anchor or at the dock, the lights and pumps need to be energized at all times, etc. the added draw of a couple 30pt dehumidifiers is negligible.
BTW, we drain ours into the shower sumps of which we have three that are always wet with the discharge from the a/c and sinks. Again the added water from a couple of dehumidifiers is negligible. You are making the assumption that without a dehumidifier draining into a bilge, that bilge would be bone dry: that is most likely incorrect for many if not most boats.

I can't argue with what works for you. My method will only work in a cool climate where it's practical to keep the cabin temperature at least 15 degrees F above the dew point - without cooking the interior and those aboard.

It keeps my shore power bill to a minimum.

[rapiti]

Leaving our cat on the hard in Grenada for the first time. We have a Meaco dessicant dehumidifier originally purchased for cold climates. Running it in the salon today, but wondering if down in one of the hulls might be better(?) High or low? I know moist air will flow to dry, but gravity?

Thanks in advance for constructive information.

[flightlead404]

Originally Posted by SKMT

My closets are louvered.

To be clear, I hardly consider slightly damp linens much of a problem. I was just describing the only symptoms of humidity I have. I will keep the computer fan concept in the back of my mind though.

Based on the replies, doesn't sound like I'm missing anything by not running a dehumidifier. Thanks for the responses everybody.

You might feel the dampness less with a different material choice (you probably are using cotton not linen). Perhaps a blend with synthetic?

Use something under your mattress though, it will grow mold. I use a material from defender, but once I got it I'm pretty sure I've seen basically the same material for use in landscaping or soil stabilization for much cheaper.

[slugsgomoo]

Originally Posted by rapiti

Leaving our cat on the hard in Grenada for the first time. We have a Meaco dessicant dehumidifier originally purchased for cold climates. Running it in the salon today, but wondering if down in one of the hulls might be better(?) High or low? I know moist air will flow to dry, but gravity?

Thanks in advance for constructive information.

When I have the boat closed up in the winter, the dehumidifier keeps everything quite dry even cabinets that are closed (but have louvers). I've not left the bilges open in the past, but I generally try to keep my bilge completely dry if possible. Because of a dripless shaft seal, generally if I don't have a leak, it'll stay dry down there long term, which is nice.

[desodave]

I've gone to the other side since my earlier post on this thread ( three years ago) and have used a dehumidifier on our new to us boat. It's a big one with an internal pump that moves the removed moisture to a sink with an overboard drain above the waterline. Part of the reason for the switch was the chore of removing and then replacing all the boat cushions/mattresses ... three (covered) pickup loads in each direction with the new boat. I open everything up internally as much as possible (inc the bilge areas), stack cushions vertically with air space around them, use Caframo Stor Dry heaters in the 2 end cabins to circulate air as much as possible, and run the dehumidifier in the main cabin. As others have said, keep the boat closed up. Auto control on the dehumidifier has kept the boat at 35% rel humidity all winter (used hygrometers in different cabins), no sign of mould and a much sweeter smelling boat come the spring. The Stor Drys may work on your cat to move enough air around for you.