Header tank net bag dangler

[specialbeat]

Hi there, I was doing a bit of tidying in the attic like you do and I noticed a net bag dangling from the rafters into the header tank. My question is, what could it be? I presume to reduce lime scale.....as you can see from the image, it's not doing a too good a job is it? Any other idea's? Also.....I think I need to invest in a lid.....at least there were no animals floating!
Thanks. Steve

 

[flameport]

Probably one of these: http://www.fernox.com/limescale-remedies/superconcentrate-limescale-preventer-450g
they require replacing often, the idea being that the chemicals inside dissolve into the water over a period of months.

 

[picasso]

Don't know about the bag but normally bits of string hanging like that are used to tie up the ballcock.

 

[JohnD]

yes, it used to have crystals in it, supposedly to prevent limescale in kettles and boilers. There is a posher version with a sort of cylinder plumbed into the pipes. I have forgotten the trade name. The crystals slowly dissolve and have to be refilled.

Edit
Polyphosphate I think.

 

[muggles]

Think you're thinking of a Combimate @JohnD