DRAGONFLY Trimarans User Forum

For a long while now we have had a slow leak from our water tank. We realised this when we checked the forward collision compartment and found a large amount of fresh water in it. The most likely source of the leak is the point where the outlet pipe joins the tank. There is no sign of a leak into the main part of the hull - there is no water seepage at the connection you can see in the compartment where the sea cocks are.

My question is this - does the aft face of the water tank form the bulkhead you see when you look into the compartment that holds the sea cocks, or is there an air gap between that bulkhead and the aft face of the water tank?

Has anyone else had this problem, and if so how did you fix it?

If it can't be fixed, it's not the end of the world - we bale the water out a couple of times a season and accept that we lose some water from the tank. But it is rather annoying!

A quick update for anyone who's interested. We found that the leak was around the fitting in the tank at the outlet. This is a plastic fitting bedded in sealant, but the seal wasn't 100%. We discovered this by removing the tank top, emptying the tank and mopping it dry. There was a lot of water in the forward compartment, enough to surround the bottom of the tank. We could then see water seeping back into the tank around the outlet fitting. There is an air gap of about 8mm between the aft face of the water tank and the forward face of the bulkhead that seals the forward compartment.

A couple of things we also noted - the tank has osmosis all over the inside surfaces. We are not planning to do anything about that.
About 20% of the screws holding the top down wouldn't tighten when we put the lid back. They were quite hard to remove and we had to drill one out as it wouldn't budge. They appear to be tapped into the GRP, so the thread in the hole is easily damaged. So far this hasn't caused any seepage around the seal.

We’ve found the exact same problems with our recently bought DF920. I think the problems have existed for a long time, and that for this reason, the previous owner never used the tank. I took the lid off, cleaned the tank, which was pretty filthy, let it dry, and re coated the inside with water based epoxy, which was deemed suitable for food preparation areas. 2 generous coats later, the tank looks like new. As Greg says, replacing the lid is a delicate process, owing to the screw thread being in the GRP.