Dripping hot water outlet.

[Les Kay]

I seem to have water dripping from the pipe that runs from the T'junction on top the hot water tank to the sump beneath the engine (the elbow joint coming off the valve in the photo). Can anyone suggest why this is happening? My simple deduction is that the end valve is a non return valve for the hot water system and that it is faulty, allowing a slow but quite constant drip. I am having overheating problems with the BMC 1500 engine and assumed it was the head gasket again, which blew last year but the engineer didn't skim the head when replacing the gasket. Could these be related, or am I facing two separate problems?

 

 

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[aread2]

The red knob looks like a Pressure Relief Valve. It's there to protect the calorifier (hot water tank).This can be activated as the water in the calorifier expands when it is heated. Most calorifier manufacturers recommend using an expansion vessel to take up the expansion of the hot water but not everybody installs one. My boat has only recently had a vessel fitted and always wept a little water from the PRV when heated by the engine, but since it is plumbed to a skin fitting the seepage was piped overboard.

It may be the water in the calorifer is being heated to a higher temperature than it was previously and so is expanding more or you may have always had this seepage from the PRV and not noticed it. It may also be that the PRV is sticking open ever so slightly due to limescale. Try twisting the red knob a turn or so; it may have an arrowon top indicating a direction to twist. This will open the valve momentarily and it should close again immediately as it it spring loaded, flushing any debris off the valve seat, allowing it to seal.

[Les Kay]

That makes a lot of sense, I have tried to release the the valve momentarily but it didn't seem to improve it. Does this mean I can install an expansion vessel close to the top of the water tank and solve the leak? Many thanks.

[Phil Ambrose]

That makes a lot of sense, I have tried to release the the valve momentarily but it didn't seem to improve it. Does this mean I can install an expansion vessel close to the top of the water tank and solve the leak? Many thanks.

In a word, yes. If you think about it, your calorifier is full of cold water, you heat it and the water expands and as this increases the volume the excess must go somewhere or the calorifier would split, so it allows the water to eject it through the PRV.

Phil