Losing fresh water through hot water tank pressure release?

Cardo

Cardo

Well-Known Member
Joined
3 Oct 2005
Messages
4,231
Location
In a plastic tub!
www.yacht-tinkerbell.co.uk
For the last couple of weeks or so (Though it may have been occurring last summer, too), I've been noticing what appears to be fresh water collecting in our bilges, causing the auto bilge pump to kick in at seemingly random intervals. I've been trying to track down the source of the water, and think I may have finally worked it out.

It would appear water is coming out through the hot water tank pressure release when the engine has been running for a little while. It seems either:
1) The pressure release has failed?
2) The water running through the engine calorifier is getting too hot and is causing the pressure release to release water

These are my theories, however I really don't know much about this side of the system. I would appreciate any advice anyone can provide. The hot water tank is probably a good 10+ years old.
 
I have a simialr problem Cardo, the temperature/pressure relief valves can fail after a while, mine's 25 years old.

The simple answer is to replace the prv, and I have a new one ready to fit. I just need to get the right tool in order to remove the old one, as it's quite firmly stuck.

However, in the interim, to stop my bilge from filling, I've attached a short length of hose to the outlet on the old prv, with a plastic container at the other end of the hose. All I do now is just empty the plastic tub every few days.
 
>However, in the interim, to stop my bilge from filling, I've attached a short length of hose to the outlet on the old prv, with a plastic container at the other end of the hose. All I do now is just empty the plastic tub every few days.

That's what I did. If the water is getting too hot the pressure relief valve will kick in, an option is turn the thermostat down. We didn't because emptying the container occasionally isn't a big deal and we didn't want it below legionnaires temperature.
 
Bear in mind that if you don't have an expansion vessel, a small leak-off each time the system warms up is by design. Our boat has a hose running into a plastic bottle in the engine bay that needs periodic emptying. The bottle is apparently made for the purpose and the holding strap has the boatbuilder's logo on it, so I have no reason to believe it wasn't original equipment. Other systems may have been designed to vent into the bilge to avoid manual emptying.

Pete
 
I've managed to get the PRV off and have taken a picture of it. This is it:
prv.jpg

As you can see, it's covered in gunk where it has been building up over what would appear to be quite an extended period of time. I think it's been leaking water for some time, but I think it's much worse now. It says 3 bar on the end of the red cap. Is this normal? If I turn the cap anti-clockwise, it "pops" about every 1/4 turn.

If it were just a slight dribble, I wouldn't mind, but the water ingress into the bilges has been substantial enough to cause me concern. And with water being at a premium around here, I don't want to be losing water for no good reason.

I've popped into the nearby chandlery, but the chap has never seen anything like it, so no luck there.

Can I try and clean it up? Is it something that needs "popping" every so often to keep working right? Is this one beyond repair? ????
 
Ahh, I see it is like FC's PRV, only mine is 3 bar, instead of 2.5 bar.

Good to see, like many other things on this boat, that it was fitted incorrectly (with the hose tail pointing upwards). I'm going to try popping it a few times, cleaning it out and refitting it. Whilst I can't point the hose tail directly downwards, I should be able to have this pointing in a downwards angle, so hopefully that'll do the trick.
 
Cardo said:
I've managed to get the PRV off and have taken a picture of it. This is it:
prv.jpg

As you can see, it's covered in gunk where it has been building up over what would appear to be quite an extended period of time. I think it's been leaking water for some time, but I think it's much worse now. It says 3 bar on the end of the red cap. Is this normal? If I turn the cap anti-clockwise, it "pops" about every 1/4 turn.

If it were just a slight dribble, I wouldn't mind, but the water ingress into the bilges has been substantial enough to cause me concern. And with water being at a premium around here, I don't want to be losing water for no good reason.

I've popped into the nearby chandlery, but the chap has never seen anything like it, so no luck there.

Can I try and clean it up? Is it something that needs "popping" every so often to keep working right? Is this one beyond repair? ????
Click to expand...
It would appear that you can get a brand new one for the princely sum of £8.55 on Amazon.

http://www.amazon.co.uk/Boiler-Safety-Pressure-Relief-Valve/dp/B003RSMA78
 
abraxus said:
It would appear that you can get a brand new one for the princely sum of £8.55 on Amazon.

http://www.amazon.co.uk/Boiler-Safety-Pressure-Relief-Valve/dp/B003RSMA78
Click to expand...

So it looks like they're not that uncommon an item. Unfortunately, local chandlery is a bit naff. We also happen to be out in the sticks of Greece, so Amazon isn't of much help, sadly.

I've tried cleaning up and replacing it, but I only seem to have made things worse! Doh! I'll try cleaning it up again. If all else fails, I'll have to isolate the hot water side of the system until I can get a replacement part.

What's the deal with stopping the calorifier on the engine?
 
Any half decent plumber's merchant will have pressure relief valves in stock. Very common on boilers and hot water cylinders.

Crud gets stuck on the valve seat. Sometimes one gets lucky and it will wash out, but the usual is it gets stuck and the valve will dribble for ever more.
 
We had similar experiences to you with hot water filling the bilges 2 years ago. My first change was to redirect the relieved hot water into the cockpit so that we knew when there was an issue. After a few weeks of valve knob twiddling the valve finally gave up and a replacement was sourced via ebay. A similar problem arose a couple of months back but this time it was caused by the pressure switch on the ageing water pump failing and over pressurising the whole system. New water pump fitted and all is now fine but I now carry spare relief valves - not so easy to find now we are, like you, liveaboards and on the move!

We can redirect the coolant so that it doesn't pass through the calorifier. Might be worth you doing the same.
 
Cardo said:
So it looks like they're not that uncommon an item. Unfortunately, local chandlery is a bit naff. We also happen to be out in the sticks of Greece, so Amazon isn't of much help, sadly.
Click to expand...
They're pretty common, although a chandlery is probably not the best place to try.

If you have a plumbers supply place, or decent hardware supplier near you, then if you take the old one along they should be able to sort you out.
 
Success!

We happened to have hired a car yesterday to go sight seeing, so during our travels we also popped into a plumber's merchant. The chap looked at me with a blank expression when I asked for a "pressure release valve", but fortunately I had taken a picture. As soon as he saw it, he produced one that just happened to be sitting on the counter next to him!

I've fitted the new one and so far (touch wood) things seem to be looking good. I've not heard the pump run whilst the taps have been off (which it used to every hour or so for a second or two) and the pump also seems to run happier. No obvious leaks and no water coming out my newly fitted overflow pipe.

Fingers crossed the bilges don't fill up again!
 
You must log in or register to reply here.

Share this page

Top