Mysterious Bilge Water

[Dean Strong]

I found water salt water in the bilge today for the second time in two weeks--about half an inch (a gallon overall), not enough for the float switch to activate the pump. I was on the boat for a week, and it was dry at the beginning of the week, and I never heard the pump come on (and I test it every time the boat is used).

I've had fresh water many times in the bilge, and have traced this leak to the screws securing the steering radiant cover. But I've never had salt water in the bilge before . . . and yes, I know it is salt water, because I purchased a Seatest aquarium floating arm tester a few years ago from my local pet store, so I could always tell if bilge water was fresh or salty.

What's strange about this water is that its sality is higher than the gauge will measure. Seawater in the Pacific Northwest is about 33 ppm; this water goes off the gauge at plus 40.

Its also bown/rust colored. When rain water finds its way into the bilge, it is pretty clear, except for the cloudiness from whatever crud is growing inbetween hull and the pan liner.

Seems like leaking thru-hull or weeping keel bolt should also be clear, not rust colored.

The area directly under the engine is dry, so its not the PSS shaft seal, or raw water intake thru-hull or hose.

All other thru-hulls are closed.

There is an antisiphon valve on the raw water line before it enters the mixing elbow. A tube runs from the this valve around the top of the engine cabinet, into an opening in the engine mount stringers. Anyone have trouble with this?

The boat gets used often, so I'm pretty sure this is not water that has accumulated in the liner, and has found its way into the bilge from heeling, etc.

Muffler? Any other ideas?

 

[navigator97]

The anti-siphon valve will leak only when the engine is running. It wont collect under the engine, but will flow around it , usually out on to the galley deck and then into the bilge. When the anti-siphon valve mounting bracket was mounted to the aft bulkhead, it causes the side of the valve to press on the bulkhead. This puts the forward threads in compression amd the aft threads in tension. Every time the engine runs, it vibrates the valve and stresses the threads more. A failure waiting to happen. If it's the AS valve leaking, replace it and mount the mounting bracket with stand off spacers behind it (a stack of washers will do) and use longer mounting screws. The higher salinity measurement may just be due to evaporation.

 

[Benny17441]

Check the rudder post seals.

 

[Dean Strong]

I don't believe there are rudder post seals on this model. The rudder sits in a tube molded directly into the hull, with a bearing at the top and bottom of the tube.

 

[ericdeaton]

i see two possibilities. the first is that sea water is leaking in somewhere that you have not yet found. there are dozens of posisbilities. the second and more interesting is that you may not have sea water in the bilge. the only thing that the seatest guage tells you is that the specific gravity of the liquid in the bilge is higher than that of freshwater. many of the liquids in boats fall into this category. Antifreeze and refrigerant, for example. you might want to check these systems for leaks. urine's specific gravity is almost identical to sea water ... so you might want ot check the plumbing lines and tanks. beer has a specific gravity hiigher than fresh water but lower than sea water. coke and most other soft drinks contianing sugar have specific gravities much higher than salt water.

 

[drumbeater]

As the clear water evaporates the salt remains and the salinity would go up. That happens in our fish tank weekly.

 

[Capt. D]

We too had mysterious bilge water that only occurred while underway, regardless of whether under power or sail. After checking the obvious culprets and after many theories were tested, we discovered that the water was coming in from the anchor locker. When the boat was built, someone drilled a weep hole a little off angle creating a hole between the hull and strakes. They tried to correct the problem by filling the hole with a compound that eventually (over 10 years) dried and fell out. When the boat moved, it forced a wave in front of it which, when sufficiently high enough caused water back through the weep hole and eventually into the bilge.

During the process of tracking down our leak, we discovered that anything, from bolt to thru-hull, that breaks the surface of the hull creates a possible leak. Good luck in unraveling your mystery.

 

[Scallywag-l36]

Oh wow, what you describe is EXACTLY the same as I have been experiencing! I have a H36 built 2004, you didn't say which boat you have?
Anyway, check out the thread I started a little while back regarding faulty seals in the Simpson Lawrence Windlass which was just one of the sources of one of my leaks.
Another culprit was the anchor chain locker, which had not been properly glassed in when the boat was manufactured, just poorly sealed which eventually gave up and allowed water into the bilge whenever I took any water over the front.
A further source I found was the pipe for the elec bilge pump; when I got beam swell, sea water would siphon in via the skin fitting on the port side. A simple and cheap one-way valve in the pipe fixed that one.
I thought I was 'home and dry' (pardon the pun) but no; STILL getting coffee coloured salt water mixed with sand in my bilge after even a slight seaway!
Then I found a fault with my Y-valve in my heads waste pipe. The connection of the Y valve to the pipe that comes from the heads was leaking. This meant that not only was nasty water from the heads flushing into the bilge (ewwww) but also any sea water forced back up the waste pipe in a seaway would end up in the bilge too!
I hope this gives you some things to check out!! If you find any new ones, let me know??

 

[Dean Strong]

I replaced the anti-siphon valve and eliminated the overflow hose, so this is not the source of the leak--alas, I thought it was. After motoring several hours on Saturday, there is salt-water in the bilge again, but no dampness below the engine (the pad is absorption pad is still clean and dry).

So now it is time to start eliminating other sources. I'm starting with all through hulls. Anyone have a good technique for doing this? Some kind of colored dye or marker?

Thanks!

 

[Dean Strong]

Might as well keep you informed with another post. Is also a way to document.

Specific gravity of tested water far exceeded sea water. Could be due to evaporation (in Seattle?) or it could be urine.

Visited the boat today and the bildge is dry, except for the slight seepage from the weep holes into the pan liner. This confirms that the leak only occurs when the boat is in motion (but see caveat below).

We have never heard the bilge pump running, but probably couldn't hear it over the engine. Cleaned and marked the bilge to see if rise in water level can be determined, to if it is making the float rise and the pump to run.

Eliminated depth sounder and knotmeter units. All dry.

Eliminated hot water heater. I thought this could be a source, but when I traced all the lines, realized that when the engine is running, the hot water off the engine is from the fresh water system, not raw water cooling (wasn't sure at first). So a leak would be green, since the fresh water system is anti-freeze treated.

Pad under the engine remains dry. Source is not directly off of the engine raw water lines anywhere.

Examined the muffler, but did not have time to completely remove. Was able to feel under and around, no water to the touch. Still, a very slight possible source, a leak would drain into the pan liner and eventually the bildge, not under the engine.

Examined through hulls and hoses: Engine raw water (but would leak to under the engine), head intake, macerator outfalll, old head discharge (hose capped off, thru-hull closes). No apparent dampness or water. Clean hull and encircled all through hulll-s with a dry-erase marker.

Some dried up leakage was apparent at the macerator. This is interesting because it has not been used in over 7 years, and through hulls are closed. Is linked to the holding tank with a Y valve, which is open to the pump out. Y valve failing, and holding tank contents leaking into macerator hose? Seems unlikely, no odors, etc. But cleaned all around macerater discharge and encircled with dry erase marker anyway.

Checked skeg bolts, cleaned hull around and marked with dry erase. No sign of leakage.

Forgot to check sink drain thru-hull! This is a possibility. Link seems to be only when the engine is running, but went day sailing twice, and had no water in the bilge. Tend to open the sink thru-hull only on overnight trips. Will have to keep a log.

Summary of Possibilies
1. pin hole leak in muflfer (but is fiberglass, not metal, not subject to corrosion
2. Similar size leak in sink thru-hull hose.
3. Macerator remains a possibility, but doesn't explain what it would leak from the holding taking only when the boat is in motion.

Will be keeping a careful log from now on.

 

[Scallywag-l36]

You haven't mentioned whether you motored into any swell, wash or waves. If so, think about possible places where water can get in. I found another one; I have a s/steel hull fitting just below the rubbing strake starboard side in the bow, it's a breather for the freshwater tank which is located under our forecabin bunk. The skin fitting inside the hull takes a 90deg turn vertically (so its 'L' shaped) and the breather pipe runs from the top of this in a swan-neck shape down to the breather in the freshwater tank. Here's the interesting part: the pipe was WAY too large diameter for the breather fitting in the hull, it had just been stuffed up with sealant and a jubilee clip tightened to hold it in place. The clip simply could not make a good seal especially once the sealant had dried out and fallen away. The breather pipe was so loose I could remove it from the fitting without loosening the jubilee clip! Whenever a wave smacked the hull or I drove the bow into a seaway, seawater entered via the hull breather fitting and it leaked past the poor seal and jubilee clip and down inside the hull. This also explained why sometimes the water in the bilges was variable salinity, sometimes quite lacking in saltiness. Whenever I over-filled the freshwater tank some would inevitably leak past the breather fitting!
Good luck , let us know how you get on!