Megaflows

[redsturgeon]

Anyone have any experience with these sealed hot water tanks.

Ours is now about 15 years old and has tarted to pour water constantly from the overflow.

We have had new valves fitted twice and they seem to cure the problem for a few months before it starts again.

John

[digitaria]

I have a conventional unvented system, not a Megaflo.

The Megaflo is unusual in that the hot water expansion is managed by means of an air "bubble" in the tank, rather than a separate expansion vessel.

Your symptoms suggest a need to recharge the air bubble. I believe that there are instructions on the tank itself, but also online e.g.

https://www.heatraesadia.com/information/frequently-asked-questions.htm
http://www.diynot.com/diy/threads/megaflo-airgap-recharging-the-bubble.159251/
http://www.diynot.com/diy/threads/water-dripping-through-tundish-megaflow-unvented-cylinder.258714/

Hope this helps.

[Philanthropissed]

We have a sealed circuit mega flow type cylinder, though ours is a OSO.

Exactly where is your overflow emerging ? We have recently had this problem, but the cause was a knackered pressure relief valve on the Boiler, rather than on the cylinder.

If your boiler has a pressure relief valve, try "jiggling" it a bit, depressing and releasing it several times, If it is leaking due to a tiny bit of scale or crud on the valve seat, this may clear it. ( we had to have a new valve fitted, as ours did not respond to "jiggling ")

And as a BTW, when our OSO mains pressurised cylinder was installed, by a cheapskate builder, it did indeed have the "air bubble" inside the cylinder. We have subsequently had an expansion vessel added, which by holding the "air bubble" outside the cylinder, has released the full cylinder capacity for hot water.

As the mains pressure feeding through the Cylinder to the shower head has admirably increased the flow, the cylinder capacity is used much more quickly especially if multiple showers are in action. Increasing the cylinder capacity by having a "remote air bubble" has boosted the effective cylinder capacity.

Anyone considering a Shower Pump, should consider the alternative of a mains pressurised water cylinder, as this will effectively pressurise the whole hot water system, including my "Steam Shower" which would otherwise have required a pump if it had not been supplied at "mains" pressure to feed the steam generator.

[redsturgeon]

Exactly where is your overflow emerging ? We have recently had this problem, but the cause was a knackered pressure relief valve on the Boiler, rather than on the cylinder.

It is leaking through the plastic tundish as shown below at 1.00 minute on the video.

https://www.youtube.com/watch?v=DFufKEIvbTo

I have tried replenishing the air gap but it does not solve the problem.

I will get another plumber in I guess.

John

[Meatyfool]

My megaflo was a nuisance at one time, but I believe I was not following the recharge instructions fully. It would need recharging very quickly again.

Make sure the gurgling ceases completely before you close the valve. Don't close it when the gurgling has slowed substantially!

Meatyfool..