searching for a leak and needing advice

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
so firstly thanks for the help. secondly we've had a very slow leak coming into our bildge. through cutting some holes in the fiberglass I've traced it to somewhere around the front cabin.

now I can't see exactly where it's coming from (I'll be dismantling the cabin bead tomorrow) but I know the bow water tank has a leak but I don't think it's that as the amount of water that we've already removed from the boat would mean it's refilling.

has anyone experienced this/ have any ideas of where to look?

I'm very confused about this and struggling to find it. any support would be much appreciated.

cheers,

Jamie
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The first place to look is the hose fitting at the tank. These can develop leaks if the clamp was not tightened or as the hose ages. We just replaced a couple fittings in the freshwater system on our boat for this reason.

Next look for places where errant screws might punctured the tank. This might happen next to a bulkhead where something is mounted. A hole of this nature would cause an intermittent leak, once the water level dropped below the hole the leak would stop.

Good Luck.
 
May 24, 2004
7,129
CC 30 South Florida
First of all determine if it is fresh or salt water as it could help eliminate possible sources. Is it a constant leak or periodic? Periodic leaks can be related to an activity or to weather for example sea spray after a brisk sail, after a rainstorm or a wash down. What do we have around the front cabin? 1) water tank, pump, hoses 2) a top hatch 3) a bow pulpit and fixtures affixed to the deck above 4) discharge thru-hulls, anchor locker? The most common sources of water reaching the bilge are 1) dislodged water previously trapped in the stringers under the sole 2) rain leaks, 3) washdowns 4) Plumbing leaks, 5) Tank leaks 6) galley spills 7) wet bathing suits, 8) shower drains 9) hull intrusions. Water leaks are sometimes difficult to locate as water pooling in one area of the boat can originate in a different part. I would check the plumbing system, pressurize it and see if the automatic pump cycles too frequently as a loss of pressure without water valves being used can only point to a leak. Check the weather stripping and beading of deck items and re- bead any suspect fixtures. Cut down on boat washes and wet bathing suits. Fixed known existing leaks like in your water tank or totally empty the tank. Do not make assumptions, just because water is coming into the bilge and you found water under the front cabin does not mean that water that is filling the bilge is the same water pooled under the front cabin. For example your boat likely has many gallons of water trapped in the stringers under the sole and some of that water may be released into the bilge by boat motion induced by a brisk sail or wave action at an anchorage. This type of water is usually salty to brackish. Good luck.
 
Dec 28, 2015
1,837
Laser, Hunter H30 Cherubini Tacoma
When I’ve found puddles and could figure out where it was originating from I’ve used toilet paper taped up in the suspected area-and it will show you even after it has dried out. I’ve also used corn starch applied with a soft brush and that will also show it.
 

BarryL

.
May 21, 2004
1,000
Jeanneau Sun Odyssey 409 Mt. Sinai, NY
Hey,

If you think it's seawater you should start with the holes in the boat - speed transducer, sonar trandsucer, water intakes (head, anchor wash, etc.), anything below the water line.

You can dry the areas and then put down tissue paper. Check back a few hours later and see what's wet.

On my last boat I new the water tank was leaking but finding the leak was very difficult. I even changed a few hoses but that didn't solve the problem. Eventually I found that the tank outlet connected to an elbow and the connection at the elbow had a slight leak. It drove me crazy until I fixed it.

Good luck,
Barry
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
If you think it is your water tank, dump a few bottles of food coloring in the tank and see if that color ends up in your bilge.
 
  • Helpful
Likes: ggrizzard

Tom J

.
Sep 30, 2008
2,301
Catalina 310 Quincy, MA
Since you don't think it is the water tank, I would concentrate on the depth sounder transducer and speed paddle wheel, both usually located under the forward cabin. On my boat, they are located under a small hatch in the forward cabin sole. They can be removed with the boat in the water, and the holes plugged with a plug on a lanyard attached to the through hull.
 
Sep 24, 2018
2,549
O'Day 25 Chicago
You could add some food coloring or UV tracer (plumbing/hardware store) to your freshwater tank to rule that out
 

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
Found the hole once we lifted the boat. A small crack in the hull.

Absolute nightmare as it's directly under The bow water tank. A mechanic in the harbour is saying I'll need to remove the whole tank (which is sealed in) to fix it from the inside.

Is this really necessary? It seems small enough to fiberglass but I don't want to bodge it.

Any advice would be amazing.
 

Attachments

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
If you think it is your water tank, dump a few bottles of food coloring in the tank and see if that color ends up in your bilge.
Yeah did this on the thruhull entry point and it showed it wasn't coming from there. Thanks for the suggestion. Found the hole. It's a small crack which is sitting underneath the water tank.
 

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
If above water line and possible outside leak, pressurize cabin with leaf blower and have someone brush everything outside with soapy water and if air bubbling out is a leak. Old yard trick to find leaks
Yeah that would be a good next step. I was wondering how people pressurise such a big space. Leaf blower would definitely do it!
 

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
First of all determine if it is fresh or salt water as it could help eliminate possible sources. Is it a constant leak or periodic? Periodic leaks can be related to an activity or to weather for example sea spray after a brisk sail, after a rainstorm or a wash down. What do we have around the front cabin? 1) water tank, pump, hoses 2) a top hatch 3) a bow pulpit and fixtures affixed to the deck above 4) discharge thru-hulls, anchor locker? The most common sources of water reaching the bilge are 1) dislodged water previously trapped in the stringers under the sole 2) rain leaks, 3) washdowns 4) Plumbing leaks, 5) Tank leaks 6) galley spills 7) wet bathing suits, 8) shower drains 9) hull intrusions. Water leaks are sometimes difficult to locate as water pooling in one area of the boat can originate in a different part. I would check the plumbing system, pressurize it and see if the automatic pump cycles too frequently as a loss of pressure without water valves being used can only point to a leak. Check the weather stripping and beading of deck items and re- bead any suspect fixtures. Cut down on boat washes and wet bathing suits. Fixed known existing leaks like in your water tank or totally empty the tank. Do not make assumptions, just because water is coming into the bilge and you found water under the front cabin does not mean that water that is filling the bilge is the same water pooled under the front cabin. For example your boat likely has many gallons of water trapped in the stringers under the sole and some of that water may be released into the bilge by boat motion induced by a brisk sail or wave action at an anchorage. This type of water is usually salty to brackish. Good luck.
This was really helpful. Thanks for breaking it down like that. Managed to find it!
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
Found the hole once we lifted the boat. A small crack in the hull.

Absolute nightmare as it's directly under The bow water tank. A mechanic in the harbour is saying I'll need to remove the whole tank (which is sealed in) to fix it from the inside.

Is this really necessary? It seems small enough to fiberglass but I don't want to bodge it.

Any advice would be amazing.
Some guidance one-sided repairs, along with the caveats that apply, is at
 
  • Like
Likes: JamieB
Jun 8, 2004
10,024
-na -NA Anywhere USA
For leak checks above the waterline, tape off hatches and put a large plastic piece over the companionway tappped down to the deck. Cut the plastic which to insert a leaf blower tube into it and tape the plastic to the leaf blower tube. Make sure all ports are secured. Have another person standing by with a bucket of soapy water with brush. Turn on leaf blower. Then brush all hardware, ports, rub rails, etc. looking for air bubbling out which is indicative of water leaks. Mark areas with blue painter’s tape to identify leaks
 

LloydB

.
Jan 15, 2006
806
Macgregor 22 Silverton
"Is this really necessary? It seems small enough to fiberglass but I don't want to bodge it."
" no worry it's just a small iceberg" comes to mind besides it seems to have that unusual shape similar to a camel's nose.
 

JamieB

.
Aug 1, 2021
46
Beneteau 400 Loano
"Is this really necessary? It seems small enough to fiberglass but I don't want to bodge it."
" no worry it's just a small iceberg" comes to mind besides it seems to have that unusual shape similar to a camel's nose.
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
Edit: I got to my laptop and was able to edit this post

It is easier from the inside but you can do a pro job form the outside. First grind out the crack until you have undamaged cloth … then fair out the grind about 1:4 or 1:6. For example if your grind is 2 cm deep, then fair out the hole to 8 or 12 cm. You will need to glue in a backing plate. See the first few pics. I made the backing plate by laying a pice of plastic film over the hole and tracing out the hole with a sharpie. I then cut the plastice with a lip about 1/4" outside the line. I then used that plastic piece to cut six patches of fiberglass cloth with that shape and wetted them with epoxy resin stacked them and let the set. I then glued the backing plate it in place with J B Weld marine.
0928120932.jpg
0928120931.jpg
0928120932a.jpg

0928120945a.jpg


I held the packing plate in place by drilling two small holes and threading a piece of dental floss through the holes. Dental floss is made of dacron. I then smeared the plate with the JB Weld and pulled the plate taught against the inside of the hull with the dental floss and let the JB set.

0928120945.jpg
0928120957b.jpg



Then I set and lay in successively larger pieces of cloth until the hole is filled in. Fair and paint. In the pic below, you can see me peeling off a piece of velum. I wetted 6 layers of cloth, each a little larger than the previous... then layed them all in the hole at once. Taped the velum over the patch to hold it in place while the epoxy set. When I peeled off the velum, I had a nice smooth surface so.... minimal fairing needed.

0928122022a.jpg
newpaint_front.jpg

I’ve done this type of repair a few times and there are some tricks to make it easier. If you want to go this route we can schedule a phone call. This fix will take you to half days. The reason it takes two is you need to let the epoxy set inbetween steps.
 
Last edited: