Megaflow valve leaking?

boomish69 · 22 Sep 2006

HI guys can anyone help I have a megaflow water tank, a slow leak has developed from a valve this is situated near the top of the tank. it seems to be a pressure relief valve made by RWC, it is in two parts the bottom being cast and joins to the flow and a discharge pipe but the top is a kinda of black plastic the projects up like an upturned glass, the top of it has a join and this is where the water is seeping from, it says RWC 3 bar on the very top.

I am unsure if this top comes off and there is a nut underneath I can tighten or maybe I have to replace this whole part if so where from?

I put in the whole heating system about 12 years ago, so it's getting on a bit , but it all works ok. i'm a chippie so good with my hands and can put pipes together ok, but am unsure of what each part of the system is.

Any help would be very very appreciated..

ollski · 22 Sep 2006

Are the insructions on how to recharge the air bubble still stuck to the side of the cylinder?

boomish69 · 22 Sep 2006

ollski said:
Are the insructions on how to recharge the air bubble still stuck to the side of the cylinder?

yes I think so, I know how to do that, I wonder if that will cure it? I doubt it the valve seems to be on the cold water pipe in.

Also I managed to remove the hard plastic out cover at the top this reveals the valve that seems to go up and down with pressure and the retainign washer that was fixed to it has completly rusted away as the water is coming from there, like a leaking tap body. I presume I shall have to replace the whole unit. it looks a very comlex thing

boomish69 · 22 Sep 2006

found the valve

http://www.rwc.co.uk/Product.aspx?page=CAT4

its the 3. 312C Series Pressure Reducing Valves

A pressure reducing valve for domestic applications, with compression connections.

looks like I can get a replacement top from the same people, pity it's a friday, gona have to be mopping up the drip all weekend..

ChrisR · 22 Sep 2006

This sort of thing

Is a pressure relief valve. The plastic cap isn't supposed to come off!
Megaflo's
DO need periodic attention, otherwise that valve lets by(down the pipe),
Can explode,
Should only be worked on by qualified people (by law),
Have changed their bits and pieces over the years.

Wouldn't like to advise further without seeing it, and would check with mfr once I had.

If you don't do the porocedure described on the side, the water has nowhere to expand to when it heats, so it comes out. The appropriate valves should be checked annually.

----------

You posted while I was typing! Not all appropriate now, but still true!

ollski · 22 Sep 2006

You know it is very important that any work on an unvented cylinder is carried out by someone with the unvented g3 ticket?

boomish69 · 22 Sep 2006

ChrisR said:
This sort of thing

Is a pressure relief valve. The plastic cap isn't supposed to come off!
Megaflo's
DO need periodic attention, otherwise that valve lets by(down the pipe),
Can explode,
Should only be worked on by qualified people (by law),
Have changed their bits and pieces over the years.

Wouldn't like to advise further without seeing it, and would check with mfr once I had.

If you don't do the porocedure described on the side, the water has nowhere to expand to when it heats, so it comes out. The appropriate valves should be checked annually.

Thanks Chris, yea I see it's not supposed to come off, was good I did tho as it's retaing washer was corroded inside, I shall have to get a new cartridge. I shall sadie a ring on Monday.
yep I recharged the gap only a month ago. and I know I'm not supposed to work on it but I put the thing in in the first place and am very carefull in what I do, I had to see if I could stop the leak before shutting off the water. the unit is buggered anyhow I think. I think last time it was cleaned out was years ago..

oilman · 23 Sep 2006

boomish69, the "valve" you have problems with is a pressure regulator, usually connected to an expansion relief valve. In that configuration known as a combination valve. The black plastic part, which is the regulator, is replacable on its own but ONLY IF YOU CAN GET IT APART!!!! I have only managed to seperate one from the valve body on a new, unused valve. Cleaning the strainer should be a routine exercise, though fortunately it's rarely needed. Even then it's difficult without causing damage to the plastic casing, so I think you will have to replace the whole thing.

The leaking sometimes doesn't occur until the pressure on the supply drops (when a tap is opened elswhere) and then it leaks as you describe, but it's a fault on the valve anyway.

Unvented cylinders have 5 safety devices if installed correctly, and then the boiler has another 2, so it's so unlikely it will explode, you are more likely to be killed by a bee sting. The valves usually leak, and people can't read the wacking great sheet on the side of the tank on how to regenerate the air bubble.

To change the combination valve, you may have to drain the tank, if the valve is low down.

boomish69 · 23 Sep 2006

Nice one oilman, yep I managed to get it apart today, I cleaned all the inside, it was full of rusty crap, I couldnt get the bottom bit out of the cast bit, so all I could clean was the top and the spring, I think it need replacing as you say. I am regenerating the gap as I type, if it's just that I will kick myself but it's never leaked like this before (I mean realy dripping not just weeping) and I did it not long ago.
made me laugh the comment about exploding, I did this was a little ott.

thanks for all your help lads, I'll post agin if the airgap regeration stops it. looking at the condition of the valve I will repace it anyhow, I wonder what other parts in in such bad condtion.

oilman said:
boomish69, the "valve" you have problems with is a pressure regulator, usually connected to an expansion relief valve. In that configuration known as a combination valve. The black plastic part, which is the regulator, is replacable on its own but ONLY IF YOU CAN GET IT APART!!!! I have only managed to seperate one from the valve body on a new, unused valve. Cleaning the strainer should be a routine exercise, though fortunately it's rarely needed. Even then it's difficult without causing damage to the plastic casing, so I think you will have to replace the whole thing.

The leaking sometimes doesn't occur until the pressure on the supply drops (when a tap is opened elswhere) and then it leaks as you describe, but it's a fault on the valve anyway.

Unvented cylinders have 5 safety devices if installed correctly, and then the boiler has another 2, so it's so unlikely it will explode, you are more likely to be killed by a bee sting. The valves usually leak, and people can't read the wacking great sheet on the side of the tank on how to regenerate the air bubble.

To change the combination valve, you may have to drain the tank, if the valve is low down.

Agile · 23 Sep 2006

"""I know I'm not supposed to work on it but I put the thing in in the first place and am very carefull in what I do"""

I find that somewhat worrying! I am not at all convinced that this poster has the necessary understanding of the requirements to be able to know if its safe or not.

Its very important that an unvented is properly fitted as it can explode. This unit has apparently never been checked since installation.

A user CAN reform the air bubble according to the instructions. It is the installation of an unvented which must be done by a qualified person who is trained to identify deficiencies and safety risks.

Tony

oilman · 23 Sep 2006

That bit you can't get out of the casting is the bit that should come out. The bit you have seperated sounds like you have managed to get apart, two bits that should stay together. ie you've broken it. Look up the rwc site for more info.

The exploding happens when the temp and pressure relief valve fails to operate, and the thermostat on the tank, the o/h stat and the control stat on the boiler all fail at once, then the t&p valve pops open when the tank is way over temp and at pressure.

If you put it in 12 years ago, and haven't done anything since, I'm not surprised you have a problem now. I also wonder if you have put the discharge pipe in properly. This is the usual drop off. It should be fitted as the manufacturer says, and be able to take full flow when the T&P valve is opened. If it can't, it isn't right.

boomish69 · 24 Sep 2006

Agile said:
"""I know I'm not supposed to work on it but I put the thing in in the first place and am very carefull in what I do"""

I find that somewhat worrying! I am not at all convinced that this poster has the necessary understanding of the requirements to be able to know if its safe or not.

Its very important that an unvented is properly fitted as it can explode. This unit has apparently never been checked since installation.

A user CAN reform the air bubble according to the instructions. It is the installation of an unvented which must be done by a qualified person who is trained to identify deficiencies and safety risks.

Tony

Don't worry the system was designed by a professional and was checked after fitting, I have also have several megaflo engineers over the years to service it. I have been in the building trade for 30 years and have seen plenty of these systems put in. my last plumber mate has moved away so am a bit stuck to call a mate round.

boomish69 · 24 Sep 2006

oilman said:
That bit you can't get out of the casting is the bit that should come out. The bit you have seperated sounds like you have managed to get apart, two bits that should stay together. ie you've broken it. Look up the rwc site for more info.

The exploding happens when the temp and pressure relief valve fails to operate, and the thermostat on the tank, the o/h stat and the control stat on the boiler all fail at once, then the t&p valve pops open when the tank is way over temp and at pressure.

If you put it in 12 years ago, and haven't done anything since, I'm not surprised you have a problem now. I also wonder if you have put the discharge pipe in properly. This is the usual drop off. It should be fitted as the manufacturer says, and be able to take full flow when the T&P valve is opened. If it can't, it isn't right.

Thanks for the post Oilman, no I managed to undo the cartridge section it comes off fine it's not broken, in the bottom cast casing is a diapram kinda things that doesnt seem to want to come out whilst in the cartridge is a plastic bit that also doesnt seem to come out, there is vertical spindle that runs up through the whole thing, the water is leaking around this, looks like a seal has gone.
The discharge pipe is in fine I know how important this has to be fitted properly and takes the full discharge fine. It's just it hasn't been looked at for a few years, I just can't afford getting ripped off. Any recomendations on getting a service guy in? it's a gloworm fuelsaver complheat 55 boiler

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Megaflow valve leaking?

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