BoilerMate 2 Water Evaporation at the Header Tank

[overthetop]

Recently inherited this system of a BoilerMate 2 and a Potterton Suprima 80 boiler, both about 12 years old.
Header tank has both ball valve and an isolation valve.
Water level in tank is about right; it is on the crease mark when cold. It does rise up, as expected when hot, but still below the overflow pipe.
A few weeks later the level has dropped again. Along with a dose of Fernox, I added some leak sealer. Level again had dropped again over the following few weeks.
I suspect, after doing a few calculations that the water is evaporating, not helped by no lid fitted to the tank’s top opening.
Any one else experiencing this, and/or confirm this as an issue with such a system?
thanks
overthetop

 

[Armo74]

I would be surprised if it is evaporation, more than likely a dodgy float valve and possibly a slight leak somewhere.

The level should only be about 4" anyway.

 

[45yearsagasman]

If the water in that tank is warm (quite common) and no lid is fitted then it is almost sure to be evaporation. Do not add leak sealer unless a leak is confirmed...................Too late

 

[overthetop]

Thanks for your comments.

The header tank does indeed get quite warm; I guess that is to be expected as the much larger tank underneath gets very hot.
I will not add any more leak sealer.
I have just added my own lid to the header tank, an inverted plastic cereal bowel. Any condensate forming on it ought to drip back down into the header tank. I have checked to ensure it don't interfere with the float valve movements.

Will further monitor the situation over the next few weeks.

thanks again

 

[Dan Robinson]

Do not add leak sealer unless a leak is confirmed...................Too late

One or two doses would do next to naff all anyway

 

[Slugbabydotcom]

They do evaporate and do need topping up between 6 months and a 2 years from my experience. Why the instructions don't allow for a conventional permanently connected to mains feed tank with an overflow I don't know.

 

[Agile]

A plate of the right size with the lip fitting inside the hole is very good and condenses on the cold china and drips back.

Topping up every six months is no problem.

A good reason not to have a permanent top up from float valve is that when they leak at 10 years old the amount of water leaking is limited.

Most have an empty interlock and will stop giving hot water if a few litres are lost and then alert to owner to the leak!

Tony

 

[Dan Robinson]

I think if 200 or so litres of sludgy boilermate leaked, tge continued rinsing of fresh water from the ball valve might actually help the clean up cause

 

[Agile]

If they have a low water interlock then that's usually only about 6 litres down and with a slow leak might have evaporated and not otherwise been noticed.

Many of the electric stores have been fitted in flats and I hate the risks of dealing with 200 litres on the fourth floor!

Tony