Hi,

I have just had a new bathroom installed, and my existing hw / ch system has been converted to an unvented hot water system. The existing radiators and pipe runs have been retained, and I am considering what I should do to achieve the following:

a) remove existing sludge and rust in the rads - some of the existing rads are old, but are still hot top to bottom. Is there any value in replacing any of them, or can they be flushed effectively? If so, how?

b) replace non-working thermostatically controlled valves - none of these seem to work reliably (either full on or off). Any recommentations regarding types and prices?

c) Use additives to help control corrosion / scale... what type, how much, and how do you use it?.

Thanks in advance for any advice.

Cheers,

Alex.

Hi
Answering your questions...
a.The best way to clean and treat the heating system is to "jetflush" it which involves, capping off the cold feed and vent pipes to "close" the heating circuit, remove the heating pump, connect two large bore hoses to the pump valves and run outside to the jetflusher, connect a mains water supply to the jetflusher, run a dump hose to the nearest drain, prime with water and turn on. The larger submersible pump runs at about 0.5 bar and enables all radiators to be flushed individually until clean water appears in the unit, also all of the pipework in the floor beneath the lowest drain point can be flushed. The flow of water can also be reversed via a lever to shift heavy deposits. A corrosion inhibitor should be added via the unit when finished, lastley reinstate pipework and heating pump.We typically charge around £350 + vat in the Bucks area.

b.Thermostatically controlled valves only ever turn fully on or off as they only sense the air temp in the room and turn the rad on or off. (may have misunderstood you). There are two types of valve available 1.with a wax filled head which is much slower to react and very cheap or 2.with a acetone filled head which is fast acting and dearer.

c.should be done as part of the flushing process.

Regards
Mog

Mog,

Thanks for your detailed answers...

I guess it sounds like a non-diy procedure for a novice then...

With regard to the thermostaticly controlled valves, I meant that anything other than 'max' seems to result in almost no flow through the rad, i.e. the temperature of the rad is tepid.

Does this mean that it is kaput?

Thanks,

Alex

Hi
Seeing as internal diameter through a TRV is at best only 5-8mm then any obstruction can have a big effect on flow, it is probably best to change the valve rather than spending too much time on it. If you air lock the system then the valve can be changed without draining down in about 10mins.
Mog

Alex,
I have copied this reply i gave to another thread,hope it helps you,it is very easy to do.

Paul

Rayman,

I have just had this problem myself on one of my houses it was a pain to sort but got there in the end.

make sure both valves are open,open and close them a few times incase of obstruction,make sure no air is in it,put the pump on no 3 and shut all the other rads and see if it gets hot.
If this does not work then you need to drain the system and pressure flush it.

Drain system remove rad take all fittings off rad and flush out finally standing upright hose in top and swilling all crud out bottom,flush the valves.

Now you have to flush the system out. put the valves back on the radiator pipes and get 3 inches of 15mm pipe and an olive and fasten a hose to the 15mm pipe jubilee all hose fittings then put mains pressure done one pipe and it will flush crap out the other do this with all other rads closed and then open and also swap the flow and return and do again.If it is a conventional system you will have to put a 22mm end stop on the vent pipe obove the header tank and also shut the 15mm mains supply off to the header tank other wise the system will not be sealed and it will find the easiest way out,not shift the obstruction and may fill your header tank up faster than the overflow can cope.

Finally refill,bleed all rads and all should be well, if so put some cleaner in the header tank,drain the system slightly so it pulls it out the tank into the system,leave in for a week then flush and refill with rust inhibitor.

Dont forget to take the end cap off the vent.


This does work as i did it last week,hope it all makes sense

Paul

Paul don't take this the wrong way BUT..the method of flushing you describe is full of potential problems.
1.Taking each radiator off individually is very labour intensive.
2.The risk of valves not shutting off properley.
3.The risk of dripping sludge/rust coloured water on the carpet as you carry each rad out.
4.Disturbing packing glands on each valve you turn.
5.Disturbing 2no. previously water tight joints when you undo the valve unions on each radiator.
6.Subjecting the heating system to 3bar+ when you flush with the mains water.
7.mains water flushing is ineffective as the water will go from where it is introduced straight to the drain off point bypassing the blockadges, as water will allways take the least restrictive route.
None of the above is meant as a criticism but something to bear in mind before engaging in.

Mog

Hi Mog,

No offence taken mate,

Couple of things though i only took 1 rad off to do it,no mess for me,they can all be taken off if you wont,yep it'll take you all day to do a system but all the rads will be pretty clean afterwards,you and i also know that plenty of ptfe and you'll have no leaks.

3 bar,the drain is open so will not see that.

Closing every rad,then opening 1 in turn until clear then closing it and moving on to next does a good job,did this then opened them all and drained from various points,drained week later and was very clean.

It is a bit of faffing around doing it like this and will take a day or more but the cash you save can be spent on the scooby.

I did a system that has been crap for years and it shifted some big stuff and the house is now warm and my tenants are now happy so i am also happy.

Didn't know you could get them flushed like you said and thought i'd created a new wonder flush system,Doooooo


Cheers Paul

Just get some Sludge remover,drain system ,add sludge remover,fill system back up and leave the heating on for a day or 2.Drain it out and refill system adding inhibitor as you do.
If you want to we usually shut each rad off and flush 1 at a time,it will get most of the gunge out.

We find this works well and is very cheap compared to British Gas power flush which is about £500!!!for a day.

Also if the system is creating excessive sludge then there might be a system design fault ,a primatic cylinder for example or the system could be pumping over into the header tank.

Duncan

For anyone out there who reads this and is thinking of adding any cleaning chemicals and/or any type of flushing PLEASE check that you havn't got a primatic hot water cylinder otherwise you will end up with the heating system water, chemicals, rust and sludge back filling your cylinder and cold water storage tank which doesn't bear thinking about cleaning up the mess.