Where does bilge water come from?

Burnham Bob

Burnham Bob

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Understand skin fittings can weep. Can't see mine doing that. Understand rain water leaks. Can't find any. Understand engine raw water leaks - none of them visible. But I get water in the bilges. I have a manual pump and the amount it delivers is misleading - lots of pumps but in reality maybe a kettle full at most usually. Keel bolts don't seem to weep either.

Surely it can't be condensation? Or can it? Even a sparkling new boat with no leaks direct from the makers has a bilge pump. So where does the water come from?
 
Prop shaft? Toe rail? Domestic water system - doesn't need much more than a couple of drops an hours for it to mount up. Is it salt or fresh water? If salt, then it's most likely to be either a weep from the engine cooling system or a stern gland or similar. If fresh, likely to be deck fittings, toe rail or leaky hatches. It might also take time to work its way down into the bilges. On our boat we had a minor leak through an ill closed port light this winter, let in quite a bit of rainwater which then took several weeks to finally make its way into the bilges: it needed repeated tacking in decent winds to tile the boat far enough to get it round the various bits it had got caught behind.
Talcum powder below where you suspect leaks to be often reveals where it's getting in.
 
Burnham Bob said:
Surely it can't be condensation? Or can it? Even a sparkling new boat with no leaks direct from the makers has a bilge pump. So where does the water come from?
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I get very little bilge water. I think that what I do get comes mainly from the ice box (I melt about 2kg per day in the summer) with a little from condensation and the stuffing gland. There is generally hardly any after a winter ashore, so what there is almost entirely derives from using the boat.

My last boat had dust in the bilges. Simpler boat, though.
 
Just think of the number of things bolted to the deck of your boat. If you had a flat roof on your house, you'd be wary about puncturing it in even one or two places, and be really careful about sealing those holes. You wouldn't dream of scattering it with eyes and stanchions and cleats and winches and cheek blocks and chainplates and sprayhood bases and winch handle pockets and throttle levers and toe-rails and mast steps and wiring plugs and air vents and all the other things we put on top of boats.

A leak-free deck is certainly possible, but I tend to regard them as guilty until proven innocent.

Pete
 
A leaking bow water bag; took me three years to suss that one. Just couldn't believe I had used so much water at the sink!

Three times last year in rough seas my floorboards were awash, with books, towels, socks etc swimming about.
I still haven't found were the deluge came in, but I suspect a leak from the anchor locker (which looks watertight). or an ill-fitting lazarette.
Certainly not a weep from deck fittings, or mast through-deck.

Good luck tracing yours.
 
From personal experience;

Calorifier not fitted with an expansion tank. As it heats up water is expelled through the PRV

Casing fracture on the high pressure side of the water pump
 
RichardS said:
Could be condensation over a 10 year period. Although even that would tend to evaporate when/if the weather turns warmer. So no. :)

Richard
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I would discount condensation, in ordinary conditions in the UK, as well. Here is a tale to explain:

I once bought a boat, about 8 years old, which had never had a bilge pump fitted. The deep bilges were bone dry and dusty. It had a deck stepped mast, no inboard, only 3 seacocks and, critically, all the cockpit lockers were self draining into the cockpit.

I fitted a bilge pump and never used it in 10 years ownership.
 
Our long keeler with a keel stepped mast and a Hoyt boom on the forededck gets a little in through those and a little through the shaft seal. We have a proper deep sump and a huge auto bilge pump. The little the electric pump wont clear is soon cleared with the Whale manual pump-it has a lower pick up.

I shall be dealing with the mast and shaft seal soon, but the Hoyt boom only lets in if we take green over the bow.
 
Without looking, I can think of 16 joints on the pressurised side of my water system, so it's no wonder that this is where most of my bilge water comes from, assisted by a poor joint I made, probably without enough tape. This is obvious, because the pump goes once every hour or so.

The syphon break in the engine intake is another occasional cause, though I now have a no-maintenance valve. On my last boat it was always the stern gland, until I fitted a Volvo seal. I tend to think that bilge water is self-replicating.
 
We got a lot of water last year through our worn rudder stock seal. Still getting a dribble, 1/2 pint a day maybe, when underway, but not enough to worry about.
 
Robert Wilson said:
A leaking bow water bag; took me three years to suss that one. Just couldn't believe I had used so much water at the sink!

Three times last year in rough seas my floorboards were awash, with books, towels, socks etc swimming about.
I still haven't found were the deluge came in, but I suspect a leak from the anchor locker (which looks watertight). or an ill-fitting lazarette.
Certainly not a weep from deck fittings, or mast through-deck.

Good luck tracing yours.
Click to expand...

+1 for the bag containing the drinking water on my boat.
It had simply chafed at a seam over maybe 8 years.
 
doug748 said:
I would discount condensation, in ordinary conditions in the UK, as well.
.
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We get a bit of condensation on the hull, under our double bunk in our aft cabin. Maybe a small cupfull after a couple of weeks.
 
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Try blue builders towel to help find leaks, good for around seacocks and pipe work. Is it salty, rainwater like or slightly salty. Other obscure leaks could be: rain or wet stuff in the cockpit locker which drains into bilge. Toe rail or hull to deck seam. Retrusse stern leaks when submerged when underway. Opening port light seals. Companion way doors/hatch where the wind blows it through gaps. From a sealed cavity (or anchor locker) that has water in it that leaks out slowly. Pressurised water system slight leak on a joint. If you cook on board a lot or have crew plus terrible ventilation then maybe condensation. Rudder post area or pintle fixings. P bracket mounting on the hull.
 
The short length of exhaust hose between the silencer and skin fitting had never been replaced but all other hose had. Due to movement when the engine was running the wire reinforcement had fatigued and penetrated the rubber, allowing leakage into the lazarette and thence to the engine bilge. It took me two years to find that one.
 
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