Water heater leak (big), wondering what to look for

[SJI Sailor]

This weekend the water heater on our C30 sprung a huge leak -- so much that the bilge pump would exhaust like a garden hose on max pressure for a few seconds in every 2.5 minute cycle. AFAIK we did nothing in particular to cause this; it was just a routine day trip. (I had suspected a very minor leak in the past, but had never pinned it down.)

The heater is a Webasto Isotherm Spa 40 liter (11 gallon). It is slightly over 1 year old (2019 model). You can see the solid stream of water coming from under the cover on the tank, in this photo (ignore the few drops of water higher up; those were from us):

http://www.tugnuts.com/gallery2.php?g2_itemId=74723

Before I start calling the manufacturer and dealer -- and taking it apart 🙂 -- I wanted to get opinions. The leak is clearly higher than, and away from, the other fittings and it definitely seems to come from something under that cover. I assume it might be either the tank leaking/coming apart, or could be a problem with the engine heat exchanger. It seems that the tank may have a 5 year warranty, if that is the issue.

Other thoughts? Has anyone had something similar? If we replace it, would you recommend to use the same Webasto model again or not?

 

[BB marine]

I would remove the heat element cover from the tank. It looks like the leak could be coming from that. Could be the heat element leaking. Possibly the screws came loose, wasn't installed correctly or the rubber sealing gasket is leaking .

 

[SJI Sailor]

Very helpful -- I'll start with that. Will update if I find out more (probably not until the weekend). Thanks!

 

[daviddri]

I had a similar problem and it ended up being a split gasket (the large one around the mounting flange). I have a troubleshooting guide from the Indel/Webasto if you want to provide your email. Also, Indel/Webasto sent me a new gasket free of charge as the parts have a multi-year warranty

 

[SJI Sailor]

That would be great, thanks David! I will message you about that. It would be great if that turns out to be the issue!

 

[iggy]

Make sure the power is off before removing the cover. I have the 6 gal one. If yours is like mine its a simple fix once you get the parts. I am wondering, did you drain the tank for the winter? If not, the water expanded the plate or the tank that holds the heating element.

 

[SJI Sailor]

Good to know about the fix and reminder about the power!

It was drained several times during the winter (we use the boat year round but I drained it when we would be away). Although it probably never fell below 40 degrees or so anyway, since I put 45 degree bilge heaters in the cabin. Interesting question, though.

 

[SJI Sailor]

Brian and David nailed it -- it was a leaking gasket. I got a replacement gasket kit from Webasto and now it is OK.

Replacing that was pretty painful on the C30. It involves reaching in under the refrigerator, around the PEX tubing, etc., holding the door in place with one hand, and then using your other hand to center it and position the gasket. And finally using a third hand to tighten the nut to hold it in place. Except there's no room for anyone to contribute a third hand, so it is "do your best".

What may be more interesting is the cause: the pressure relief valve was capped by the dealer. When the boat was new, we noticed a leak there and the dealer "fixed" that by simply capping it, saying that it should not overflow!

What they did not know or say is that it is SUPPOSED to leak during normal operation (according to the Webasto service notes). I intended to revisit their "service" to see if that cap was really OK, but then I forgot. So the pressure caused by heating went out through the gasket and eventually blew it.

The design has that routine pressure relief / leak going uncaptured onto the plywood. I don't like that, so I installed a 2 cup food container to catch it. (Eventually I would like to fit a hose going to the bilge, but haven't yet found an appropriate elbow connector for the tight space). So now there is a new daily maintenance item: empty the overflow cup.

 

[Osprey]

The pressure relief valve should only leak if the pressure is excessive. So the solution is to address the pressure issue. Starting from cold the system is normally full with no “room” for expansion. As the engine is run the engine coolant heats up the water in the tank. This causes the water to expand which leads to an increase in pressure.The pressure can easily reach the point for the relief valve to open. One solution is to install an expansion tank at some convenient location in the water lines. Another solution is to install a pressure relief valve in one of lines, cold or hot, does not matter. A hose can be connected to this added valve allowing relieved water to to be directed to the bilge. I have done both. An added advantage of the expansion tank is that the water pump’s pulsing action will be reduced.

 

[SJI Sailor]

Oh, that makes sense (and would be nice if the factory installed one, but I digress).

Do you have a size recommendation? When I search for them I find many that are one gallon or two gallon, but that seems very large for a boat with 11ga hot water.

It will perhaps be good to do this at the same time that I put in an accumulator tank sitting in a box 🙂 That is waiting for a rainy weekend sometime.

 

[Osprey]

An accumulator acts like is an expansion tank.

 

[SJI Sailor]

Sounds good. Maybe I'll put the accumulator in first and see how much it helps. I guess the good news is that maybe (!) there is no leak.

I've also been wanting to put in some shut-off valves -- I see ones that include pressure relief, so that might be a nice thing somewhere the lines are exposed to bilge (e.g. engine room). Thanks for the notes!

 

[iggy]

Brian and David nailed it -- it was a leaking gasket. I got a replacement gasket kit from Webasto and now it is OK.

Replacing that was pretty painful on the C30. It involves reaching in under the refrigerator, around the PEX tubing, etc., holding the door in place with one hand, and then using your other hand to center it and position the gasket. And finally using a third hand to tighten the nut to hold it in place. Except there's no room for anyone to contribute a third hand, so it is "do your best".

What may be more interesting is the cause: the pressure relief valve was capped by the dealer. When the boat was new, we noticed a leak there and the dealer "fixed" that by simply capping it, saying that it should not overflow!

What they did not know or say is that it is SUPPOSED to leak during normal operation (according to the Webasto service notes). I intended to revisit their "service" to see if that cap was really OK, but then I forgot. So the pressure caused by heating went out through the gasket and eventually blew it.

Thats why I was wondering if it froze.

The design has that routine pressure relief / leak going uncaptured onto the plywood. I don't like that, so I installed a 2 cup food container to catch it. (Eventually I would like to fit a hose going to the bilge, but haven't yet found an appropriate elbow connector for the tight space). So now there is a new daily maintenance item: empty the overflow cup.

 

[SJI Sailor]

I think you are right, Iggy, it could have been caused the same way by freezing. That was unlikely for our boat, since it never got that cold over the past winter. But it will be a good thing to watch out for in the future!

 

[Osprey]

With respect to adding an inline relief valve one should use a valve which opens at a pressure less than the tank installed valve. I used an adjustable valve which I set to open at 60 psi. I would not recommend a higher setting.