Where's my water gone!?

[gary955]

Since I re-sited the bleed screw on my back boiler heating system and filled it with a 30% antifreeze solution, it's been working much better and I'm more relaxed about leaving the boat for the weekend in freezing weather.

However. It's now using water! The header tank level is dropping, perhaps by as much as a litre a week!

I know that antifeeze can get through a gap that water can't, I pulled up a couple of weeping joints when I first filled it, but I can't find any external leaks.

Pretty much all of the pipework is accessable for inspection. Only a small section to the calorifier is out of sight and there is no evidence of water in the bilge below that. Antifreeze leaks are usually detectable by the sweet smell, especially in the cramped still air of a boat, but no such smell is apparent. There is one slightly "wet" compression joint on a radiator that won't pull up, but no evidence of an actual drip.

I don't think the calorifier coil is leaking internally because surely if so the (pressurised) water in the calorifier would back fill the (unpressurised) water in the heating system and cause the header tank to rise, not fall.

I dont think the water is evaporating because the header tank, which is the only part of the system which is vented, never gets very hot.

I also don't think the back boiler is leaking into the stove, as there is no evidence of water inside the stove even when it's been left to cool down for a couple of days.

The stove has been run continually for days at a time this winter and has given no trouble other than the mysterious vanishing water!!

I really haven't a clue where it's going.......any ideas?

[Chalky]

Crack in the back boiler that's opening up when hot and allowing coolant into the fire and then closing when cool?

[BEngo]

SNIP

There is one slightly "wet" compression joint on a radiator that won't pull up, but no evidence of an actual drip.

SNIP

I really haven't a clue where it's going.......any ideas?

Your answer's there- a litre a week is about what you'll lose from a weep, (or possibly a seep) like this, even with no drip. If it starts dripping you'll be looking at least a litre every 24 hours.

 

N

[arpeeuk]

I had a similar problem and fixed it with radweld.

 

I let the header tank go dry so there was capacity in the system to get the radweld into the circuit then got the system hot and added radweld followed by topping up with antifreeze mix. Put the circulation pump on to give it all a good mix and kept my fingers crossed.

 

It did the job and I haven't needed to top up since (5 months).

 

Hope this helps

 

Rik

[David Mack]

Are you sure its not an expansion issue? Whenever the system gets hot the water expands. If the header tank is full when cold that expansion will all overflow, and when it cools down, the water level will fall. If you leave it everything will be fine, but if you top it up the same will happen again.

[MtB]

If that

 

Are you sure its not an expansion issue? Whenever the system gets hot the water expands. If the header tank is full when cold that expansion will all overflow, and when it cools down, the water level will fall. If you leave it everything will be fine, but if you top it up the same will happen again.

 

If that was the case, I think it would have done it before adding the antifreeze too...

 

MtB

[gary955]

Thanks for the ideas, all of them plausible.

It's not the header tank rising and falling with thermal expansion though. It has space for a good 5lts of expansion and anyway I would have seen the evidence of an overflow.

I really hope it's not a cracked back boiler. Now that the warmer weather is here I'll see if the water loss continues with the stove off.

I wonder if the wet joint could leak enough for me not to see evidence of the leakage? A litre is 1000grams. Over a week that would be a gram about every 10 mins.......a gram is quite a lot, I just measured it. Could a gram disappear without a trace in 10 mins? maybe it could if it was hot. I'll try to pull the olive up again.

[Chalky]

I'll try to pull the olive up again.

 

Drain it down and remake the joint with some sealing compound re-fill, then test.

 

Is there a lid on your expansion tank? It's not evaporation is it, especially if it's on for hours at a time.

[Iain_S]

(snip)

I wonder if the wet joint could leak enough for me not to see evidence of the leakage? A litre is 1000grams. Over a week that would be a gram about every 10 mins.......a gram is quite a lot, I just measured it. Could a gram disappear without a trace in 10 mins? maybe it could if it was hot. I'll try to pull the olive up again.

 

If the system is hot when it leaks, a lot of the water will evaporate. In a house setting, I spent weeks finding leaks in the central heating after we changed to a pressurised system. Most of the leaky joints were dry; the only clue was traces of green on the copper pipe.

 

Iain

 

P.S. a gram of water is only a millilitre

[gary955]

Bugger!! Looks like it might be a cracked back boiler! I went for a cruise recently with the stove off and cold. The engine heated the calorifier, which in turn started a thermosiphon back through the heating system, warming the back boiler. At the end of the day there was a patch of damp ash at the back of the stove fire box. No free water though so I suppose it could be condensation (he says,in a sort of straw clutching way)

Anyone changed a back boiler in a squirrel? I found an online guide with photos, which looked straight foreward, but of course it used a brand new stove. The reality on my clagged up stove might be very different and considerably more messy!

[BEngo]

Bugger!! Looks like it might be a cracked back boiler! I went for a cruise recently with the stove off and cold. The engine heated the calorifier, which in turn started a thermosiphon back through the heating system, warming the back boiler. At the end of the day there was a patch of damp ash at the back of the stove fire box. No free water though so I suppose it could be condensation (he says,in a sort of straw clutching way)

Anyone changed a back boiler in a squirrel? I found an online guide with photos, which looked straight foreward, but of course it used a brand new stove. The reality on my clagged up stove might be very different and considerably more messy!

Simple job, but absolutely filthy. The boiler will come out of the door hole, but you have to be real good at origami and Rubik's cube to work out how. Easiest to take the top off, which you can only really do with the boiler disconnected and tipped into the fire space.

 

The bolts will all be corroded away and seized in. An angle grinder is the best weapon for removing them. When you grind the heads off the shank usually frees itself up as the bolt gets red-hot.

 

Don't do the new bolts up too tight. Renew the stove rope round the top too.

 

Spare boiler are usually cheapest from Harworth Heating.

 

N