Megaflow losing air gap

[dorsetchappie]

My house was constructed in 1992 and has a hot water supply through a Megaflow CL210 Indirect cylinder heated by a Stanley oil fired range. Since we moved here some 15 years ago I have experienced loss of the air gap in the Megaflow and a local plumber advised me to partaily drain the cylinder to re-establish the air gap. This is successful, but over the last few years the loss of the air gap is becoming more frequent, requiring me to carry out this procedure 2-3 times a year. The tell tale signs that this needs to be done is a dripping overflow and additional initial pressure on opening hot water taps. As soon as I re-establish the air gap both the overflow stops driipping and the pressure in the tap returns to normal.

What causes the Megaflow to lose its air gap and therefore what can be done to prevent this from happening?

 

[Ockyvines]

This is not uncommon with megaflos.
They usually have instructions on the side on how to re-charge them.
Turn off the water to it, open a hot tap, open the relief valve on the side (I think this is a lever on early ones), hold open until gurgling stops. turn on water supply again and then close the hot tap when water comes through.
A couple of times a year is ok

 

[dorsetchappie]

Thanks Ockyvines.

That's what I do, but in my case I use a drain cock situated near to the base of the Megaflow and then I connect it to a hose which leads out into the garden!

 

[oilman]

you say a Stanley range I would ask if this is a vapourising or pressure jet Stanley? The first should not be connected anyway.

 

[dorsetchappie]

Its a Stanley Super Star 80,000 BTU's that provides for central heating, hot water and cooking. It was installed when the house was constructed in 1992. It is regularly serviced by a Stanley contactor and I don't know whether it is vapourising or pressure jet.