Webasto isotemp spa water heater burst

[KlaassyC]

On our recent weekend trip, our hot water tank burst. It was winterized properly and had worked well before so I’m wondering if the pressure relief valve failed? Is there a way to test this? Or should I just replace it every few years to prevent a tank failure?


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[Gin]

I can't recall anyone posting before about a "burst" water heater. What burst exactly? Might help forum members in offering insights.

Gini

 

[KlaassyC]

At the top of the heater (behind the removable cover that covers the electrical connections and element) there is a gasketed ‘plug’ about 4” in diameter that seals to the tank with a clamp. The tank and sealing surface have bulged enough that the seal is broken and water sprays out.


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[Gin]

The Webasto manual recommends opening the pressure release valve once a month to dislodge lime and other deposits. Seems like the more common issue on the forum is that the valve doesn’t seal tightly if crudded up, rather than sticks shut. The expanding hot water then overflows a bit into the bilge. But maybe crud can cause the pressure valve not to open so that the gasket blows instead. If you don’t get any helpful ideas on the forum, you might try calling Sure Marine in Seattle (https://www.suremarineservice.com/). They are a dealer for the units, repair them, sell replacement parts, and provide technical support. They have a good reputation and might narrow or pin down the cause of your burst.

Gini

 

[knotflying]

I exercised that pressure relief valve at least once per year. When I left the boat for long periods of time I would empty the water out of my water tank and the heater. The best way to do that was to open the relief valve and then the drain valve with a pan under it. It takes a while to dump the water out, but the tank gets emptied and the valve is exercised. A win/win.

 

[Gin]

Once a year seems like plenty. Good suggestion!

 

[KlaassyC]

Thanks for the tips, I’ll be making sure it works regularly.


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[H28]

Replacing that seal is an easy fix. I did it myself last year.