Closing sea cocks while at anchor

[DAKA]

Its taken me 11 years of boating to sort this one out so I thought I'd best share it .
When I get to an anchorage the hot water tank is full of scalding hot water.
By morning its warm.

I guessed water passing under the hull at anchor was causing a raw water cooling circuit, possibly only a trickle gets passed the impeller but enough to cool the contents of the hot water tank.

This week I have closed the seacocks at night, and great news..........hot water in the morning

So who already knew and had kept it to themselves ?
Or is this the type of useful stuff you learn on a day skipper course , perhaps I need to rethink and get some training

 

[sailorman]

Its taken me 11 years of boating to sort this one out so I thought I'd best share it .
When I get to an anchorage the hot water tank is full of scalding hot water.
By morning its warm.

I guessed water passing under the hull at anchor was causing a raw water cooling circuit, possibly only a trickle gets passed the impeller but enough to cool the contents of the hot water tank.

This week I have closed the seacocks at night, and great news..........hot water in the morning

So who already knew and had kept it to themselves ?
Or is this the type of useful stuff you learn on a day skipper course , perhaps I need to rethink and get some training

service your raw water pump is the wear plate worn

 

[Talulah]

I'll expect a follow up post in a few weeks along the lines of "When you've turned off your seacocks to keep the hot water hot, don't forget to open them again before weighing anchor. Guess how I know?"

 

[capsco]

Surely much simpler and safer, to isolate the calorifier coil with a pair of ball valves, same result but not a problem if you forget to turn them back on.

 

[DAKA]

service your raw water pump is the wear plate worn

Should be alright, not done huge hours and always clean water but thanks for the tip, I will check, if the inside cover plate is good I presume the inner wearplate is alright ?

 

[DAKA]

I'll expect a follow up post in a few weeks along the lines of "When you've turned off your seacocks to keep the hot water hot, don't forget to open them again before weighing anchor. Guess how I know?"

I always isolate the engine when the seacocks are closed but there is always a chance.

Thanks for the tip capsco, I suppose one washing machine isolation valve on either pipe would do.

 

[jmac]

Hmm,

Unless I've misunderstood there may be a problem here.

I'm assuming that there is an anti-syphon loop in the raw water circuit. If not, it would be worth fitting one. If there is one, check its functioning since it should stop this kind of flow (unless the current is really strong?? - strong enough to push the water over an loop well above the waterline).

HTH

 

[blueglass]

personally wouldn't rest easy at anchor with seacocks closed. if anchor drags in the night you might need to fire those engines up rapidly without faffing around with seacocks (assuming you remember they're closed!)

 

[Geoffs]

Its taken me 11 years of boating to sort this one out so I thought I'd best share it .
When I get to an anchorage the hot water tank is full of scalding hot water.
By morning its warm.

I guessed water passing under the hull at anchor was causing a raw water cooling circuit, possibly only a trickle gets passed the impeller but enough to cool the contents of the hot water tank.

This week I have closed the seacocks at night, and great news..........hot water in the morning

So who already knew and had kept it to themselves ?
Or is this the type of useful stuff you learn on a day skipper course , perhaps I need to rethink and get some training

I can't really see this, Pete. Any raw water flow is only going to be through heat exchangers, no where near calorifier circuit. May make engines cool down quicker, but they are going to cool down anyway.

But you say it works, so much for theory! Must be something else going on.

My hot water cools down over night, but still ok for a shower in the morning.

Nothing said on my Gay Skipper course, but then that was centuries ago, before we had engines.

Must be those dodgy old Cummins engines, best swap for VP. Then again, maybe not!!!

 

[VicS]

Its taken me 11 years of boating to sort this one out so I thought I'd best share it .
When I get to an anchorage the hot water tank is full of scalding hot water.
By morning its warm.

I guessed water passing under the hull at anchor was causing a raw water cooling circuit, possibly only a trickle gets passed the impeller but enough to cool the contents of the hot water tank.

This week I have closed the seacocks at night, and great news..........hot water in the morning

So who already knew and had kept it to themselves ?
Or is this the type of useful stuff you learn on a day skipper course , perhaps I need to rethink and get some training

Something a little worrying here.

You seem to have a trickle of water through the system when at anchor.

BUT where is it going ?

Into the exhaust?.......very possibly siphoning as I doubt if there would be enough pressure from water merely flowing past the hull to force water through.

If its siphoning it'll do it when moored up in marina berth too.

If its siphoning slowly all the time wont the exahaust system slowly fill and then the engine ?

I think a check on the antisyphon loop and siphon break valve is called for.

I'd continue to always shut the inlet seacock until the antisyphon system is checked and sorted if I were you.