FW Tank Leak - Krogen Manatee

[SamIam_Sam]

Hello. A couple months ago, I began to notice water in the bilge. The bilge pump would run from tine to time but definitely more often than normal. I traced the leak to the starboard FW tank on the other side of the gen room bulkhead (see photo attached).
Dilemma: There is no access to the tank beside what you can see in the picture. My mechanic says we would have to cut a bigger hole to expand the existing opening in the bulkhead to get to the fittings and the tank to diagnose the leak.
Question: Are there any other Krogen owners who have had experience with leaking, inaccessible FW tanks? Is it more likely to be a fitting or an actual hole in the tank? Any recommendations on diagnostic steps other than cutting away the bulkhead?
My FW supply is now depleted in a couple of weeks whereas prior to the leak, the supply would last 4-6 weeks. I could just continue refilling the tanks more often but would like to fix the root cause.
Thanks for any advice the group may have.

 

[Larry M]

I agree with your mechanic. First thing, remove the insulation at the fitting. Then you will probably have to cut a section of the plywood that is behind the insulation. Neither one of these is a big deal. You can use a Feintool or equilvant to do both. If your tanks are fiberglass, it should be an easy repair... we’ll as easy as anything is on a boat. Keep us posted.

 

[HiDHo]

You should have stainless steel tanks BUT not all Manatee’s are alike. We have a small deck hatch in the forward starboard side ofthe salon and port side under the built in settee. Our hatches give access to the tank cleanout covers, if you have this setup you can determine if the tank is f/g or metal. Your photo shows a tank suction that’s like ours, we have a ball valve instead of a globe valve and a sight glass.
Knock on wood we have no tank leaks. One thing I practice is slowly filling the tanks to avoid violent oil can effects.
Keep us posted once you find the leak.

 

[healhustler]

Agree with above. I also have the inspection plate under the built-in settee. If your tanks are still the original stainless, the most common leaks come from the welded corners, which are of a bit lesser quality than the stainless itself. Bill also remarked about guarding against the oil-can effect when filling, and this is likely to be a great contributor to the stress of those welds. My tanks are OK so far, but a video snake and some epoxy weld can go a long way toward solving the problem once the leak is located. Stay in touch.

 

[diver dave]

The tank doesn't oil-can when filled slowly?? That's curious.

 

[HiDHo]

diver dan, I think fast fill pressurizes the tank because the vents are only 1/2” hose and the bronze deck fittings with screened openings are a further restriction. Also fast flow to the point of overflow will definitely cause oil canning, Not a good thing on any welded seam tank.

 

[SamIam_Sam]

STBD FW Tank

It took me a while to figure out what y'all meant by "oil can" but now I totally get it. It seems I always hear that "thong" as the tank fills no matter if I fill it slowly or with the hose at full blast. In fact, that's the signal that the tank is nearly full.
Funny thing is though... I hear the same thing after some period of time as the tank is emptying as well. Just last night I was in the salon and "thong" meaning the water level is going down. But since this is a very slow leak, the speed at which the tank is emptying is not a factor. Maybe I will clean out the air vents just in case there is some blockage preventing timely pressure normalization.
Getting back to the problem at hand... here is a picture of the clean-out port in the top of the tank accessible from the salon. It appears to be galvanized steel rather than stainless but maybe this is what 30-year old stainless looks like. No luck in it being fiberglass which would be an easier repair depending on what the cause of the leak is.
Thanks for the info and advice. The investigation will continue into the new year. Speaking of which... Happy New Year!

 

[HiDHo]

That’s stainless, identical to our tanks. I hope your leak is at the suction pipe threaded fitting, not a weld.
Good idea to make sure the vents are open. The port and starboard bronze vent fittings in the cockpit are a prime target for spiders, mud dabbers, etc. I was surprised that the identical bronze vent fitting for the fuel tank is not on the starboard side below the diesel tank fill fitting but on the port side, good to know if it burps during fueling.
Happy New Year
Bill

 

[healhustler]

Yeah, stainless. Looks the same as mine too. My tanks always oil can on filling and draining too, but under high pressure fill, much more violently.

 

[Pack Mule]

Not a manatee but I feel your pain. Both of my water tanks are shot . Hopefully yours is just the connection.

 

[Boat]

Paper towels are my low-tech leak detectors. Tuck them in and see where they get wet first. Assume water flows downhill but it can fool you.


Food color might could be used but it could get messy.


There are electronic water leak detectors but I have no personal experience with them. I suspect an ohm meter could be used but the conductivity of the water may need to be altered.

 

[stubones99]

Paper towels are my low-tech leak detectors. Tuck them in and see where they get wet first. Assume water flows downhill but it can fool you.


Food color might could be used but it could get messy.


There are electronic water leak detectors but I have no personal experience with them. I suspect an ohm meter could be used but the conductivity of the water may need to be altered.

Cut up strips of cardboard box as your water detection strip, since it darkens when it gets wet. Better than paper towels and tends to lay flatter. It also looks different when it has been wet.

 

[Larry M]

If you have to gain additional access into the tank for repairs, Seabuilt makes an access plate system for up to an 18” cut out.

Seabuilt - Access Plate Systems

 

[SamIam_Sam]

Found it!

Bottom corner weld apparently. What is the best method of repair?

 

[Larry M]

Can you get to the inside? I dropped a butcher knife, point down, into a ss sink. It actually stuck in vertically. I used West Systems epoxy. It lasted for the 10 years we owned it. I know most epoxies aren’t recommended for potable water tanks but if it’s just for a repair? JB Weld?

 

[HiDHo]

Larry do you think this is an example of crevis corrosion ? The photo showes a lot of corrosion. I’d be tempted to have a welder take a look at this tank if the other corrosion hasn’t compremised the tank.
Sam, what year and hull # are you ? We are hull # 69
I’m hoping behind our tank bulkheading we don’t have the same corrosion problem.

 

[Larry M]

Bill: I don’t know if it’s crevice corrosion or an inherent problem with the welding of ss. We had a sailboat with 2-75 gallon ss tanks. We developed a leak and fortunately the designer/builder made it easy to take the tank out with out having to remove any major joinery though still a pia. The leak was along a seam. We had a piece of 1” angle iron welded along the failed seam/pin hole leaks. When we sold the boat 10 years later the tank was still good.

I’d get a guy who was good with a tig welder and ask him. I feel Matt’s pain.