I have a 16yr old Megaflow Indirect Cylinder 170litres. Water is heated from a gas boiler. The tank is leaking slightly and it appears to be coming from the side electic element connection, although as it is sealed with insulation it is difficult to tell. The tank air bubble disappears after about a month or so no matter how much I drain from the tank - I usually drain to just below the release valve. It appears that when the bubble dissappears the tank will start to leak. The pressure relief valve does not expel water. Cold water pressure is 3 bar. Is it worth repairing, or should I replace the cylinder.
Leaking Megaflow Cylinder
- Thread starter Jimmysgc
- Start date
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is the leak from the immersion heater connection?
as the air bubble is lost, then the expanded water has nowhere for it to go so can cause a leak, but the expansion valve should OPEN and release the water/pressure - twist the prv/expansion valve and see if it is working
your air bubble could be being lost constantly lost due to the leak in your cylinder
as the air bubble is lost, then the expanded water has nowhere for it to go so can cause a leak, but the expansion valve should OPEN and release the water/pressure - twist the prv/expansion valve and see if it is working
your air bubble could be being lost constantly lost due to the leak in your cylinder
Can I just point out you are required to have a G3 certification to work on unvented cylinders, as these can be turned into a timebomb if you cok anything up
good point from John506 - I have an Unvented card but very good point. Lots of safety devices on these cylinders
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I have a Megaflo Mk 3 CL170 from 1994, exactly the same model and last year I had exactly the same problem. There was an intermittent dribble of water from the same area - around the immersion element port weld (not the thread), and it had lost the air bubble and discharging out of the TP valve.
So, after reading posts on what Heatrae Sadia themselves did on a new installation of a Megaflo with air bubble problems, I did 2 things that have sorted out the problem.
1. I fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)
2. I tin snipped the outer layer of metal that covers the insulation and removed some of the insulation around where the leak was coming from and was able to expose the leak - on a seam where the immersion port is welded onto the main cylinder body. I have used 'Leak Fix' on this area and now, with the help of the pressure not going over 3 bar (because of the extra expansion vessel), it has not leaked since. I also fitted a pressure gauge so I could keep an idea on what was going on.
So, after reading posts on what Heatrae Sadia themselves did on a new installation of a Megaflo with air bubble problems, I did 2 things that have sorted out the problem.
1. I fitted an additional EXTERNAL expansion vessel suitable for the hight pressures of unvented cylinder (NOT the red one used for Central heating sealed systems)
2. I tin snipped the outer layer of metal that covers the insulation and removed some of the insulation around where the leak was coming from and was able to expose the leak - on a seam where the immersion port is welded onto the main cylinder body. I have used 'Leak Fix' on this area and now, with the help of the pressure not going over 3 bar (because of the extra expansion vessel), it has not leaked since. I also fitted a pressure gauge so I could keep an idea on what was going on.
No, before anyone mentions it , I'm not G3.
But the installation was done originally by a G3 bloke who notified the council etc, yet he had failed to install an important safety device, so as far as I am concerned, after rectifying the installation and adding an additional vessel plus pressure gauge, I have only made it somewhat safer than the original certificated install.
But the installation was done originally by a G3 bloke who notified the council etc, yet he had failed to install an important safety device, so as far as I am concerned, after rectifying the installation and adding an additional vessel plus pressure gauge, I have only made it somewhat safer than the original certificated install.
The vessel for unvented must withstand at least 10 Bar, as that is what it will reach before a safety device discharges.
The warranty on a Megaflo is now 25 years but the ones supplied then it was conveniently only 10 years!!
I used the product called 'LEAK FIX', comes in a tube, you mix a hardener etc. From normal DIY shop.
The warranty on a Megaflo is now 25 years but the ones supplied then it was conveniently only 10 years!!
I used the product called 'LEAK FIX', comes in a tube, you mix a hardener etc. From normal DIY shop.
Try explaining that to the courts.
*******s. The original installer can show himself in court. I have made an unsafe installation safer. It is not uncommon that I find certificated electrical work / gassafe or G3 work done officially that is unsafe. I suspect that a small but significant minority of 'tradesmen' think that because they have the ticket and insurance & an employer behind them, then they can do a rush job without really caring about doing it properly or safely.
As far as I remember the t & p is 10 bar and the pressure relief valve is 8 bar... could be 8 and 6 but do you really want me to go downstairs and look in the cupboard? It's a very old megaflo with different specs from current ones.
The relevant part of this discussion is that if you put an external expansion vessel onto a megaflo, it needs to cope with higher pressures than those experienced on a CH system, which would only reach 3 bar before the prv operates. A megaflo's operating pressure is 3 bar.
The relevant part of this discussion is that if you put an external expansion vessel onto a megaflo, it needs to cope with higher pressures than those experienced on a CH system, which would only reach 3 bar before the prv operates. A megaflo's operating pressure is 3 bar.
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