fernox ds3 descaler

[Stephen]

Hello,

I have moved into a house with an unknown CH history. The cylinder may be 30 years old like the house, then again, it may have been fitted the day before I moved in. It is a very hard water area.

I see you can buy fernox ds3 to descale potable hot water. Is it worth trying some of this? Or is it a case of "if it's not broke, don't fix it"?

I have not looked inside the cylinder to see if scale is a problem for two reasons: removing the immersion heater would require emptying the cylinder and that seems a waste of hot water. Secondly, I think I read here that if you remove immersion heaters they can be a pig to fit back and if you cross thread them, you need to buy a new cylinder: ouch!

Is it worth a bit of preventive maintenance with DS3? If so, will the small 250g (?) B&Q pots be enough or do I need a trade 2kg tub?

Thanks, Stephen.

[Andrew Gabriel]

I use DS-3 for descaling various things from time to time, but I've never put it inside the house pipework. It takes lots of rinsing to get rid of it, and you'd probably end up flushing through many tank fulls to get it out of your hot water cylinder. It has a dye so you can see it's there and tell when it's spent (it's an indicator which changes colour from yellow to green), and it has a smell added, again so you can tell it's present.

I buy 2kg tubs because it works out much cheaper, although in the last few years, no one seems to stock it anymore so you have to go to mail order, or get a wholesaler to order you in a tub. Actually, I just bought 3 x 2kg tubs from BES (only one for me -- some collegues also wanted some having seen me use it). Those 2kg tubs are probably the cheapest way to buy Sulphamic Acid.

[Dave Plowman (News)]

Well I live in London where the water's pretty hard and my cylinder is 30 years old and never had the potable side descaled. Still works fine.

Is there a reason why you want to?

[Dave Liquorice]

Turn off the cold supply to tank and drain down to below the level of the immersion boss, if that's on the dome it's not very much water.

They can be pigs to get out. IIRC the best tool to use is an immersion socket spanner rather than a ring spanner, crack the joint before you drain as the water, in theory, provides a bit of support for the cylinder. Clean all the threads and mating surfaces before replacing and use plumbers mait and a bit of care and cross threading shouldn't be a problem.

Personally I wouldn't bother with either the descaling (yuk, descaler in your DHW supply) or looking. Unless the reheat time is very long, by that I mean >1hr from incoming mains temperature cold.

[Stephen]

Unfortunately, rather than have one big immersion heater going down from the top, my cylinder has two smaller immersion heaters: one near the bottom and one higher up. To check the bottom one would require draining most of the water. OTOH as the other poster said, I would have to drain it to flush it out afterwards, so I guess draining can't be avoided.

I guess the ring type of spanners are no use now that cylinders come sprayed thick with foam.

Can you use plumber's mait on immersion bosses? I thought it was for dirty water joints?

Do you mean reheat by immersion heater or reheat by boiler? We do use economy 7 with the immersion heaters so I have no idea whether it takes seven minutes or seven hours. I will have to try to reheat during the day when I am awake to monitor it.

Thanks.

[Dave Liquorice]

No just take drain enough to remove the top one and use a torch and small mirror. I guess these two go into the sides as an E7 setup.

I was thinking via a boiler as E7 had not been mentioned before. Nothing like leaving pertinant facts out to get duff answers in return.

Not sure how you'll tell then unless there is some indication when the stats in the immersions have opened. Which isn't usual. Running water out to see how hot it slows down the reheat as you are introducing more cold...

[Michael Chare]

I would not try to remove an immersion heater that is working as you risk damaging the tank during the removal. I would suggest living with whatever scale has built up.

[Dave Plowman (News)]

Surely you could just add it via the header tank if you must - drain it down first to avoid too much dilution. You don't drink water from that - so flushing should be just as effective - or not - for both hot and cold.