Adding noise reducer through expansion tank

[zebra]

How do you know when you have drained enough out of your central heating system to add noise reducer additive through the feed and expansion tank? Two storey house with tank in loft. I don't want to drain too much, because the system already has corrosion inhibitor in it. But clearly I need to get down far enough for the noise inhibitor to reach the circulating part of the system. If I drain to the level of the upstairs rads, will this be far enough? Thanks for your help with what must be one of the simple-minded questions ever!

[Owain]

"zebra" wrote | How do you know when you have drained enough out of your | central heating system to add noise reducer additive | through the feed and expansion tank? Two storey house | with tank in loft. I don't want to drain too much, | because the system already has corrosion inhibitor in | it. But clearly I need to get down far enough for the | noise inhibitor to reach the circulating part of the | system. If I drain to the level of the upstairs rads, | will this be far enough?

Instead of discarding the fluid that you have drained and refilling from the mains, turn off / tie up the ballcock and drain off a bit (but not so much that air is sucked in) from the bottom of the system into a jug, then return it, with additive, to the top. Drain a bit more and repeat, running the pump occasionally. This way you won't lose your corrosion inhibitor.

Owain

[zebra]

That's fine and thanks, but I still need to know how much to take out of the system to get the additive down to the level it will be circulated to the boiler?

[Owain]

"zebra" wrote | > Instead of discarding the fluid that you have drained and | > refilling from the mains, turn off / tie up the ballcock and | > drain off a bit (but not so much that air is sucked in) from | > the bottom of the system into a jug, then return it, with | > additive, to the top. Drain a bit more and repeat, running | > the pump occasionally. This way you won't lose your corrosion | > inhibitor. | That's fine and thanks, but I still need to know how much to | take out of the system to get the additive down to the level | it will be circulated to the boiler?

The volume of the tank + the volume of the pipes leading from the tank to the circulating part of the system + a bit more for luck.

If you can drain the tank from full to just-above-outlet, probably that about 3-4 times will do it. Or until you get bored :-) If access to your tank is good you can do it by the bucket. Try not to make waterfall as you empty bucket back into tank as this will oxygenate the water, which is not what is wanted.

Owain

[zebra]

Thanks. I'd just about got there myself and was trying to remember how to calculate the volume of water in 8 metres of 15ml ( pi 7.5 squared X 8000 = 1.4 litres?). I've got a couple of capped 5 litre bottles, so I'll fill them three or four times down by the boiler tap and make a few trips to the loft, adding two litres of noise stuff after the first draining of the expansion tank. Wish me luck!

Cheers,

A