How do you drain the Calorifier

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Rafiki

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in the context of winterising lots on here talk of 'draining the calorifier' , but how do you do this? On mine I couldn't find an obvious drain plug on the calorifier itself so last winter made do with pumping all the water out of the system through the taps and then leaving the taps open all winter ashore. Should I be doing something else?
Boat stored ashore, east coast, so a few days of - 5 to 10 might be anticipated in a bad year.
Andrew
 
Two options, both use the pressure relief valve which is normally at the bottom of the calorifier.
Just draining it takes for ages, and rarely gets it all out. I use a small 12v pump, which I attach to the valve and suck the stuff out. The yards in Sweden attach a pressure line to the valve and blow it out through the taps with compressed air.
 
I take out the anode (some do, some don't). The PRV never empties the tank. Really I should have a drain downstream but I suspect that would vacuum lock (however that works). Removing the anode allows air into the tank as it empties - not nice to put fresh water into a wooden bilge!
 
The fact is you don't need to drain it completely just to winterise it.
All you want to do is avoid the water inside expanding to the extent that it hydraulically bursts the calorifier.
So as long as you leave enough ullage in the top, partial drainage will be plenty. I generally go for about half full just to be sure.

I generally use the prv, located about half way up the tank. It's a bit of a fiddle because you have to hold the red turny knob in just the right position to open the relief valve fully. But only takes minutes, maybe up to 15-20 ish.
Be sure to have the taps open at the same time to allow air in, otherwise it'll take much longer
 
Trundlebug said:
The fact is you don't need to drain it completely just to winterise it.
All you want to do is avoid the water inside expanding to the extent that it hydraulically bursts the calorifier.
So as long as you leave enough ullage in the top, partial drainage will be plenty. I generally go for about half full just to be sure.

I generally use the prv, located about half way up the tank. It's a bit of a fiddle because you have to hold the red turny knob in just the right position to open the relief valve fully. But only takes minutes, maybe up to 15-20 ish.
Be sure to have the taps open at the same time to allow air in, otherwise it'll take much longer
Click to expand...

You're right about the calorifier, I think. What concerns me more is avoiding that water remains in the lowest part of the piping, where the pump happens to be. I try to blow out as much water as possible by disconnecting the pipes and using a small compressor.
 
On my yacht, Hanse 341, the calorifier is at the stern , so when you look at the side elevation, you can see that the calorifier is higher than the floor of the heads. So when draining the water system and I get to the stage that the water pump is beginning to splutter, I put the shower head on the floor, open its tap and the cold water tap in the galley and when I finally switch off the water pump, I get a syphon effect so that most of the water from the caloifier ends up on the shower floor, so I can just use the shower pump.

The final water I drain off using the pressure release valve and normally only a cup full or so comes out. I go with the view above that it is ok if there is a bit of water in the tank, as it not restrained and so can freeze without causing any damage.

As I do occasionally get some seepage through the PRV, I have run a pipe from it and then out through the stern shower head transom fitting.
 
Rafiki said:
last winter made do with pumping all the water out of the system through the taps and then leaving the taps open all winter ashore.
Click to expand...

That will not drain it. When the pump has emptied the main tank it pumps air through the calorifier, which emerges from the top, leaving all the water in there. If there is no tap the best way is to remove the cold water inlet hose and let the water out to the bilge, pumping it out from there.

There are a couple of nice photos of the consequences of inadequate draining here https://coxengineering.sharepoint.com/Pages/Calorifier.aspx Hoses will take a bit of freezing normally but elbows and other joints will not, they may blow off or split. A plastic nozzle on the accumulator in my motorhome split like this, needing replacement of the unit.
 
On both my current and previous boats there is a drain valve (almost certainly a domestic central heating drain valve) on the cold inlet which is at the base of the tank. I'd suggest worth adding if you don't have one. I drain the tank fully using a cheap Draper 'drill pump'. I didn't one year, and although the tank was OK the seal around the immersion unit got strained somehow so it leaked badly when refilled in the Spring.
 
Would this work? With the boat ashore, connect 3-4 m. of garden hose to the pressure relief valve, take the other end over the coaming and down to ground level, suck hard to start a siphon, go for lunch?
 
Well thanks for all your input, I must try and locate the PRV, or failing that simply disconnect the lowest pipe and drain from there, should be fun in the bottom of the cockpit locker !
Andrew
 
A mass of water in a tank is very unlikely to freeze hard in southern UK. A very light output heater will easily prevent freezing, even a 10w lightbulb beneath the tank will keep it warm enough.

Or if you are worried about the pipes then a 50:50 mix of polypropylene glycol pumped through will stop anything freezing and can simply be pumped out in the Spring.
 
If you are struggling to get to the bottom of the tank I have removed the Emesion heater in the past and sucked it out from there it needs to be a least half empty to give air space if needed I also but a small tube heate at the side of it hopefully that will stop it freezing
 
My calorifer lies on its side in a difficult to access space under a berth. I cant easily get to the pressure release valve drain and both hot outlet and the cold inlet are towards the top of the tank so I cant use gravity to extract water. Instead I use the dinghy pump to force air thru the cold inlet which pumps a lot of water out of the hot water outlet.

if I'm really keen, the overall weight of the calorifier is then considerably less and I can undo the clamps which hold it in place and i can lift it to pour the water out
 
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Without being too insensitive.. how often does the winter location of the OP experience serious frost?
On the Clyde we rarely get more than a few days <-3C so some greenhouse heaters on a thermostat solve most of the hazard. It does not take too many Watts to keep the ambient >0 ?

Alternatively borrow some compressed air and blow all your water overboard?
 
Noting that you are ashore, remove the impeller log. Put a piece of garden hose through the hole to the ground below. Connect the other end of the hose to the inlet pipe to the calorifier. Then turn the pressure relief valve on the calorifier to allow air to enter. The calorifier will drain fairly well, although depending on the levels at which your pipes run, you may have to start the siphonic action with a good suck! It helps if you've already run the taps dry before doing this. Good luck.
 
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