Megaflow

[ub7rm]

I have a megaflow hot water tank and during / after the boiler was heating the water there was some discharge from the tundish and the first time a hot water tap was opened there was clearly a release of pressure. I got the plumber to recharge the air bubble when he was servicing the boiler and all was well ... for maybe a week then the symptoms gradually have come back.

I'm guessing a recharged air bubble should last longer than a week - any ideas whats wrong with it and is it fixable?

I suspect its a bit tricky to recharge this fully as its a bungalow and the tank is located in a cupboard in the house (i.e. not the loft) so the lowest outlet is not really that low relative to the tank but still - I would have thought it would have lasted longer.

 

[Madrab]

You need to get a qualified engineer to service the cylinder, might not just be the air bubble. Safety systems may need looked at.

As long as the lowest tap is below the mid point of the cylinder and you can empty the tank below the level of the relief valve then recharging the bubble should be pretty staightforward

 

[simond]

When the bubble runs flat - inevitable with this silly design, which is why there is a label on the outside telling you it is normal - there is a good chance that the PRV will refuse to seat properly once the first discharge has occurred.

This results in it dribbling, especially when the cylinder is being warmed because the internal pressure will be at its highest.

The other possibility is the control group is letting too much pressure in from the mains, but this is less likely. The first problem is almost inevitable if you own a Smegaflo. Which is why I refuse to specify this particular product for my customers.