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MichaelG

Best way to dry out a cabin bilge

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Hi all, my boat is a trad stern with a conventional layout IE from the stern, bedroom. bathroom, kitchen and saloon. The bedroom has two inspection hatches into the cabin bilge, one under the steps into the engine room and one under the wardrobe which is against the bulkhead between the bedroom and engine room. So about as far astern as you can get before you get into the separate engine bilge. I regularly check the inspection hatches and they've always been dry since we've owned the boat, about two years. Last week I noticed there was water in the cabin bilge under the wardrobe. The boat does have a slight list to port so any water would tend to find its way there. There wasn't much, probably about two litres which I mopped out. Apart from the obvious but hopefully unlikely cause that theres a hole in the hull I'm thinking a number of possible causes,

A leaky window although theres no sign of any leakage around any windows. We have had a lot of very heavy rain.

Leaky heating system. I have had to top up the expansion tank on the Alde boiler.

Leaky domestic system although the water pump doesn't cycle randomly.

Lastly I recently had the fresh water pump replaced as the last one packed up. It may be the engineer may have been a bit careless when replacing it and dumped a bit of water into the bilge in the process.

I thought about putting some air vents in the cabin floor to assist drying but Ive read two contradictory theories.

Vents are good because they will cause a flow of air through the bilge aiding drying out.

Vents are bad as they will introduce warm air from the cabin space into a cold bilge, result condensation.

Any thoughts, advice and ideas others have tried gratefully received.

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Personally I wouldn't choose to have permanent vents in the floor, it would make the cabin colder. What I did when I wanted to dry mine after a water leak, was to use an electric fan heater on its COLD setting. With the aid of Sellotape I used a bin liner, with the bottom cut off to make a big short tube, as a duct between the fan and one of the two inspection hatches. The air travelled the length of the boat before emerging at the front, and I left it blowing for 3 days to be certain the whole bilge was dry.

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I did similar once, using a computer fan over a round access hole, running continually for a few days. The low current meant the batteries easily coped with the load.

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2 hours ago, MichaelG said:

Vents are bad as they will introduce warm air from the cabin space into a cold bilge, result condensation.

 

2 hours ago, Keeping Up said:

I wouldn't choose to have permanent vents in the floor, it would make the cabin colder.

 

Goes against my O-level Physics thinking; warm air rises, no?

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2 hours ago, MichaelG said:

Leaky domestic system although the water pump doesn't cycle randomly.

I have had a water pump leak from the pump body without affecting the outlet pressure and hence making it cycle. Without this warning it dripped a considerable amount of water in to the cabin bilge before it was noticed. A leak from the pump, or anywhere back to and including the tank could do this.

 

Jen

 

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33 minutes ago, Sir Percy said:

 

 

Goes against my O-level Physics thinking; warm air rises, no?

Warm air rises but we nothing is absolute. If you cut a large hole in the floor would it make the boat colder or have no effect? What about if you remove the floorboards entirely? Likewise if you put a vent in the floor there will still be some circulation of colder air into the cabin even though warm air rises. How significant that will be in terms of making the cabin colder I'm not sure.

Edited by blackrose

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1 minute ago, blackrose said:

If you cut a large hole in the floor would it make the boat colder or have no effect? What about if you remove the floorboards entirely? Likewise if you put a vent in the floor there will still be some circulation of colder air into the cabin even though warm air rises.

If there were a heat source, that would cause air movement upwards. Having a floor vent near to the stove and another floor vent some distance away, would provide air movement through the bilge, which would help to keep it dry. You see this arrangement in Victorian front rooms. Trade-off between warm cabin/dry bilge.

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4 hours ago, Sir Percy said:

If there were a heat source, that would cause air movement upwards. Having a floor vent near to the stove and another floor vent some distance away, would provide air movement through the bilge, which would help to keep it dry. You see this arrangement in Victorian front rooms. Trade-off between warm cabin/dry bilge.

That of course is assuming that the dew point of the air entering the bilge is higher than the temperature of the steel

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6 hours ago, Sir Percy said:

If there were a heat source, that would cause air movement upwards. Having a floor vent near to the stove and another floor vent some distance away, would provide air movement through the bilge, which would help to keep it dry. You see this arrangement in Victorian front rooms. Trade-off between warm cabin/dry bilge.

 

My bilges are bone dry and I don't have any vents in the floor. It's all a bit unnecessary.

Edited by blackrose

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18 hours ago, blackrose said:

 

My bilges are bone dry and I don't have any vents in the floor. It's all a bit unnecessary.

That's an answer to OP (whose bilge is not bone dry) about putting in floor vents, not about convection.

Edited by Sir Percy

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30 minutes ago, Sir Percy said:

That's an answer to OP (whose bilge is not bone dry) about putting in floor vents, not about convection.

 

It was an answer to both. I'm saying that natural convection through floor vents isn't required to dry out bilges or to keep them dry. 

 

Last time I had water in my cabin bilges I put some nappies down there and after that put a large fan over an inspection hatch nearby for a few days and forced air into the bilges to dry them out.

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15 minutes ago, blackrose said:

 

after that put a large fan over an inspection hatch nearby for a few days and forced air into the bilges to dry them out.

so, another means of moving air through (and out of an exit, I assume).

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Hi all, thanks for the suggestions. Been down to the boat today and lifted some floor boards to try to find the source and found under the shower room was very wet. The waste water pump from the shower is one of those that sits in a plastic box with a float switch activated pump. A little while ago I noticed I couldn't hear the pump kicking in when showering. I found the float switch had jammed and fixed it. Thought I had noticed it straight away but maybe not and some of the shower water ended up in the bilge and has just found its way through the concrete slab ballast to the rear inspection hatch. Ive mopped it out best I can with limited access between the slabs and left the floor up and inspection hatch open for ventilation. Ive bought a 12v bilge blower and will pipe that into the inspection hatch next time I,m there to force some air flow through. 

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Waste of space those pumps in a box. They always end up flooding the boat. Much better a Whale pump and a manual switch rather than rely on a float.

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7 hours ago, Sir Percy said:

so, another means of moving air through (and out of an exit, I assume).

 

Yes that's right but you didn't assume it, I stated it in my previous post.

Edited by blackrose
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7 hours ago, MichaelG said:

The waste water pump from the shower is one of those that sits in a plastic box with a float switch activated pump.

Yet again...

 

Bin it and fit a Whale Gulper. 

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To EVERYBODY OUT THERE with a sump box:

If it doesn't work BIN IT AND FIT A GULPER.

If it does work BIN IT AND FIT A GULPER.

If you don't know what you've got, check it now and if you've got a sump box:

   BIN IT AND FIT A GULPER

 

  How do I get it to display in flashing red?

  • Greenie 2
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On 30/11/2019 at 17:03, dor said:

I did similar once, using a computer fan over a round access hole, running continually for a few days. The low current meant the batteries easily coped with the load.

With this, do you push air into the bilge or suck it out?  During my continued investigation of the boat over the weekend all bilge holes looked dry except near the bathroom where its not wet, but you can see its damp and I'd be really interested in getting something going to remove this dampness...

 

(I've got a Gulper)

Edited by robtheplod

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3 hours ago, robtheplod said:

With this, do you push air into the bilge or suck it out?  During my continued investigation of the boat over the weekend all bilge holes looked dry except near the bathroom where its not wet, but you can see its damp and I'd be really interested in getting something going to remove this dampness...

 

(I've got a Gulper)

I think mine sucked, but it probably doesn't make a huge difference.

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If you have access to mains power (or an inverter with the engine running), then a dehumidifier will dry the bilge (and rest of the boat) out quickest.

 

If you use a dehumidifier on a bost, make sure you block all vemts first (I use folded bathroom sponges in the mushroom vents and blutac cardboard over the low level louvres). If not the dehumidifier will try to dry the world.

Edited by cuthound
Clarification

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34 minutes ago, cuthound said:

If not the dehumidifier will try to dry the world.

Which will take a very long time as the world is rather wet. Also, it will keep filling up the water trap and where are you going to empty it?

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14 minutes ago, robtheplod said:

knowing my luck I'll use my dehumidifier, which will overflow it's tank and drain .. into the bilge... :)

 

My dehumidifier has a tank and a flexible drainpipe, which overrides the tank.

 

I put it on the draining board with the drain in the galley sink, so it drains directly overboard.

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