Desludging the central heating

[helenl]

I have been told I have sludge in my rads. I have purchased a de-sludging liquid, but don't really know what to do with it. Do I have to put it into the cold water tank in the loft after draining the system as I have no loop system to force the liquid through into the the rads. Can someone assist please.

 

[nstreet]

Which product did you purchase out of interest.

if you have an open vented system, which I suspect you do as you mentioned a cw tank, you would normally drain down the system, put the desludging chemicals in the f&e tank and let the system refill.

You would then run the system for a period of time, as per manufacturers guidlines and then drain down again. You then refill and drain down until the water runs clear.

After the final drain down, put some inhibitor in the f&e tank and then refill, job done.

Make sure you put the chemicals in the correct tank, if you are unsure run the hot water for a while and see which tank fills. This is the hot water supply tank, your f&e tank will be the other one.

If you are using Fernox DS40 (superfloc) beware if your system is old, as it can be quite aggresive if left too long and you may end up with pin hole leaks in the heat exchanger or pipes. Sentinel X400 would be a safer bet is better as you can't overdose the system.

 

[helenl]

Thanks for that, I have brought Sentinal X400 for the job. Sorry to be thick but what to you mean by f&e tank would this be the one in the loft?

 

[nstreet]

If you have an open vented system you would normally find two water tanks in the loft, one if for the domestic hot water and the other for the heating system, this is the feed and expansion (f&e) tank.

 

[helenl]

Thanks so much for your advise. I will run hot water and check the tanks. Would it be worth turning the water off whilst we run the central heating down so the f&e tank doesn't refil and then put the chemicals in and then put the water back on?

 

[nstreet]

Most plumbers would get a length of wood to span across the tanks and tie up the ball cock, with string, to stop the tank filling.

 

[Dave33]

A question, please.
If Fernox DS_40 was used and small leaks did appear in the heat exchanger, what would you do? Would a leak additive help?

 

[nstreet]

Personally I would replace the heat exchanger, if small pin holes have appeared, it could be that some of the other metal is so thin, it could give way at any time and produce more leaks.

 

[JohnD]

Helen - about identifing the Feed and Expansion - if you have two tanks in the loft, one will be to supply the bathwater, so will be 3 or 4 feet long, nearly as wide and deep. The one for the CH system only contains enough water to allow for expansion and contraction of the water in the pipes and rads, so will be about 2ft x 1ft x 1 ft deep, a bit like one of those old-fashioned toilet cisterns (and may have sediment at the bottom). If you can't see a tank like this, or if the water doesn't seem to drain out of it as you drain out of the bottom of the CH system, come back and ask again.

 

[helenl]

JOhn

Thanks I have looked in the loft and identified the f&e tank. I am going to attempt the drain and refil this weekend so hopefully all problems will be solved and I will not have to bleed my rads again!!!!