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Water in Bilge

My 60 foot narrowboat is just under 2 years old. I recently found that the "builder" had vented the pressure relief pipe from calorifier down under the floor of the boat. A fairly substantial amount of water had collected in the bilge and also travelled into adjacent compartments. I have cut hatches in the floor, removed ballast bricks and dried out as much as I can although some foil backed lagging between the ply floor and cross beams has held some residual damp. Other than a complete strip and refit of the entire floor, does anyone have any suggestions as to my best course of action (other than taking the builder to court).

Asked by: peter willard  | 8.38pm, Sunday 13 January

WW says:

I am sorry to hear that you have water in the cabin bilge- any boatbuilder should know that water will vent from the calorifier, especially when heated by engine.
You have done the right thing- the only option now really is to keep the bilge ventilated. It might be worth considering putting some vents into the bilge forward, and also aft- ideally, if you can fix some forced ventilation aft, that will draw air through and help remove remaining moisture- and is good practice to ventilate any bilge- something often ignored by many boatbuilders. Even without having a PRV leaking into the bilge, many Narrowboats and barges have condensation inside the shell collecting in the cabin bilge over a period of time.
I have seen a solar powered vent, roof mounted and run to a length of hose to the aft bilge, which provided an effective draw through of air. Also, depending on the layout of your boat, if you had a solid fuel stove, you might be able to use that to draw air through- a vent to the bilge near or behind the fire should help pull air through.
A low-power computer type fan installed in a locker aft, connected to run whenever you are on the boat, could also provide a means of drawing air through- you could use smoke matches with the vents furthest from the fan to see how effective it is in pulling air through.
I had a leak from my water pump last year, and the bilge did fairly quickly dry out with the fixed vents at both ends of the bilge. Also, being a fairly new boat, it should not suffer too much. You might want to discuss this with your boatbuilder though, as they may have done similar things with other boats they have built, and they may want to contact the owners.

Mark Langley  | 9.33AM, Monday 14 January

Another neat way to provide some bilge ventilation is to cut some holes in the floor at the back of the fridge. The heat dissipated by the fridge heat exchanger will draw cold air up from the bilge into the boat. This ventilates the bilge and the cool air makes the heat exchanger work better, and the fridge will be more efficient as a by product!

Rupert Smedley  | 10.56AM, Monday 14 January

I don't know if your builder followed the common practice of laying the ballast bricks on building felt but, if he did, you may find that the bilge will take a long time to dry out completely.
I once worked on a boat that had developed a serious leak around the shower. I cut a one foot square hatch in the floor by the rear bulkhead, removed some bricks and as much felt as I could reach and mopped out the bilge with a sponge.
Two or three days later, there was about the same amount of water under the hatch so I mopped it again. This went on for about two weeks until the area under the hatch remained dry.
The problem is that water is held in the narrow gap between the felt and the baseplate and takes a very long time to seep out. The good news is that it did eventually dry. I made sure that the hatch was easy to remove so that the owner could check the bilge from time to time. I also added some floor vents as Mark and Rupert recommend.

Graham Booth  | 11.52AM, Monday 14 January

The size you propose sounds fine, some gauze fixed over the hole will prevent things falling down the hole.

Rupert Smedley  | 2.12PM, Monday 14 January

Readers say:

Thank you very much for both of your very quick responses. I will follow the advice given - having already left the hatch I cut next to the bilge pump partially uncovered I will make new ones in the front of the boat and behind the fridge. Would you think vents in the floor about the size of a house brick would be sufficient, or should they be larger?

peter willard  | 11.20AM, Monday 14 January

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