leak to bilge in head

Oct 20, 2025
6
Beneteau Oceanis 370 Meaford
Hi. In my new-to-me 1991 Oceanis 370, there is water (note that this is on the Great Lakes, so all water is freshwater) leaking into the bilge in the head. After a few days of sitting at dock, 3 or 4 inches accumulates. Water is very clean. Jabsco head functions normally. This bilge has its own pump, operated by a button on the sink pedestal. The pump is old, slow and due for replacement, but does the job. What would be your attack plan for locating this leak?
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,453
CAL 35 Cruiser #21 moored EVERETT WA
I'd get a bright flashlight and begin looking in all the places I can imagine are sources of water.
  • It may be rainwater.
    • Check the walls, ceiling, and corners of the boat.
    • Check deck openings and fixtures that are above or close to the area of the interior
  • It may be lake water
    • Now you need to get on your knees and explore all the openings and voids near the waterline.
    • Through hulls are suspect
  • It may be water from your plumbing.
    • Fresh water lines and valves will leak your fresh water, both hot and cold, into the boat.
    • Faucets are the usual suspects.
    • Is the stored water shrinking in the storage tank?
Good luck. On my boat, water has found a way to leak uphill from the source.
 
Jun 25, 2004
588
Hunter 306 Pasadena MD
I managed to find a leak recently by taping plastic over all the places nearby (on the outside of the boat) that I suspected, and waiting for rain. I sort of did it in a few stages until it stopped. The might work, unless the water is traveling from a long ways away.

I had also thought about taping pieces of colored tissue paper (Xmas wrapping tissue) along various entry paths in the bilge, but this was for water ending up in the bilge. If yours is ending up on the floor of the head, you might try it there, around the edges.
 
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Oct 20, 2025
6
Beneteau Oceanis 370 Meaford
Thanks. Heading back to the boat in a couple of days. I was thinking of using talcum powder or something similar to find the direction the leak is coming from.
There's no good way to tell if my freshwater tanks are leaking because the amount pooling in the head is a "drop in the bucket", so to speak, but I think it's more likely to be head seal or similar.
 
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