Megaflo Hot Water tank type CL 170

[Makman]

Hi, I have a Megaflo Hot Water Cylinder in the loft, really pleased with it but it does present one annoying problem.

More or less every month I have to turn off the water supply to the tank, drain the tank down with the vent open and re-charge the air expansion cushion.

I would understand if I need to do this once a year, but every month is a bit of a pain.

The signs are, it starts to spill water via the relief valve, which appears onto the patio from a free drain pipe.

I have no idea how the air can eascape, as I have checked all the possible leakage areas, pipe fittings etc and no leaks have been detected.

The relief vavle works, but where does the air cushion disappear too, can anyone help????

Cheers.

 

[Jeronimo]

The air does not leak from the tank but it slowly dissolves into the water going through the tank reducing the expansion volume until there is too little to take up the pressure increase caused by heating the cold which comes into the tank. The pressure is then relieved by the relief valve.

How are you draining the tank?

When I first had mine, the advice was to shut the cold water inlet, open the nearest hot water tap then re-charge air into the tank by holding open the relief valve on the side of the tank. After standing there till I thought the gurgling had finished or I was fed up, I would let go the RV and refill the tank. Not long before it needed doing again.

Now, I know when the tank needs recharging 'cos when I'm the first to turn on the hot tap in the bathroom the water flow gives a rush then slows down. (Normally, the rush continues).

I then choose a time when we don't need hot water for a few hours and go get my 10 inch stilson (pipe wrench). Shut off the cold, open a hot and put the stilson carefully onto the RV knob so it just grips enough and the weight of the horizontal handle is enough to hold the RV open. Then go away for at least 2 hours or until there is no glug to be heard for 10min.

Lasts at least 9 months. Mine is a 210 litre tank.

HTH

Jerry

 

[simond]

Welcome to Megaflo, they really are a cr@p design.

Designed to fail.

You can fit an external expansion vessel, I believe Heatrae sell a kit for problem installs.

Other things to check are no leakage from PRVs, and that the incoming control set is keeping the pressure under 3 bar.

 

[Makman]

The air does not leak from the tank but it slowly dissolves into the water going through the tank reducing the expansion volume until there is too little to take up the pressure increase caused by heating the cold which comes into the tank. The pressure is then relieved by the relief valve.

How are you draining the tank?

When I first had mine, the advice was to shut the cold water inlet, open the nearest hot water tap then re-charge air into the tank by holding open the relief valve on the side of the tank. After standing there till I thought the gurgling had finished or I was fed up, I would let go the RV and refill the tank. Not long before it needed doing again.

Now, I know when the tank needs recharging 'cos when I'm the first to turn on the hot tap in the bathroom the water flow gives a rush then slows down. (Normally, the rush continues).

I then choose a time when we don't need hot water for a few hours and go get my 10 inch stilson (pipe wrench). Shut off the cold, open a hot and put the stilson carefully onto the RV knob so it just grips enough and the weight of the horizontal handle is enough to hold the RV open. Then go away for at least 2 hours or until there is no glug to be heard for 10min.

Lasts at least 9 months. Mine is a 210 litre tank.

HTH

Jerry

Thanks for that Jerry,

I will give it one last go, but do believe that I drain it sufficiently, but will double check on this, this failing, then it will be the case of adding an external expansion solution.
Again thanks for the comments and help.

Scott

 

[Makman]

Welcome to Megaflo, they really are a cr@p design.

Designed to fail.

You can fit an external expansion vessel, I believe Heatrae sell a kit for problem installs.

Other things to check are no leakage from PRVs, and that the incoming control set is keeping the pressure under 3 bar.

Hi Simon,
thanks for the advise and is along the lines that I had been looking at.
With the external expansion vessel, then there is no possible escape for the air cushion.

Thanks got the advise

Scott