Non-motoring > Draining down & flushing a central heating system.	Miscellaneous
Thread Author: Dog	Replies: 43

Fri 10 Dec 10 09:38   Draining down & flushing a central heating system. - Dog

Is what I'll be a'doing over the weekend, its an 11 year old jobbie with the cold water + F & E tank in the loft. None of my 10 rads have got a drain orf point so I'm a'gonna just go for the lowest rad and fix a hose pipe or something to it somehow. I'll tie up the ballcock in the F & E tank and open all the bleeding bleed valves of course. Oh, and I've had some Sentinel X400 in the system for the last 4 weeks and I'll use the X100 Inhibitor as well, so, Anything else I need to watch out for por favor? Reply to this message | Report message

Fri 10 Dec 10 09:42   Draining down & flushing a central heating system. - smokie

Aha - I'm thinking of a partial drain (upstairs only) this morning to replace a stuck TRV. Not something I've done before but seems silly to pay someone to do what should be a relatively simple task. Will keep an eye on this thread. Why are you doing it? If to flush, are you using a machine? Some of my downstairs rads have previously had an accumulation of crud, which necessitated removal of the rad and a good flush outdoors Reply to this message | Report message

Fri 10 Dec 10 09:46   Draining down & flushing a central heating system. - Dog

>>Why are you doing it?<< I had a new pump fitted but when he switched the system back on, the pump started to scream through lack of water (obviously why the old pump failed) turns out the F & E tank was full of crud - hence the Sentinel X400. No, not using a machine. Last edited by: Dog on Fri 10 Dec 10 at 09:48 Reply to this message | Report message

Fri 10 Dec 10 09:53   Draining down & flushing a central heating system. - Fenlander

No drain points at all Dog? I've never seen a system without one somewhere. Anyway if so it's going to be a real problem not to make a mess. I assume you're going to split one rad valve off the rad to do this?? Not easy to connect a hose to either side of that bell joint so are you thinking of draining to a container? The water keeps flowing for ages. It would be well worth fitting a drain point when you have it drained down to help in any future work. Are you sure one point will drain all the system? In our place the main pipework is in the ceilings and there are 5 drops to various areas so 5 points to drain off. We've recently done a boiler change with loads of new rads. I ran a cleaner in it for a week or so, drained down, ran again for another day with clean water, then drained again to get every last bit of crud out before a final refill with the conditioning fluid added. Ideally you should add your X100 into the system via a rad bleed point not just putting in the header tank. Last edited by: Fenlander on Fri 10 Dec 10 at 09:54 Reply to this message | Report message

Fri 10 Dec 10 10:02   Draining down & flushing a central heating system. - Dog

Cheers F/L ... luckily my lowest rad is in the conservatory which has a tiled floor :) Yes, I was going to split a rad valve off, and I might even fit a drain off point while I'm at it. >>Are you sure one point will drain all the system?<< No, not really F/L, as a lot of piping goes below floor level. I was going to add the X100 to the F & E tank - then drain off water from a rad to get it in the system. Reply to this message | Report message

Fri 10 Dec 10 10:08   Draining down & flushing a central heating system. - Fenlander

>>>No, not really F/L, as a lot of piping goes below floor level. In that case worth doing the interim refill and run for 24hrs before final drain to make a better job of flushing the cleaner chemical/crud. >>>I was going to add the X100 to the F & E tank - then drain off water from a rad to get it in the system. It is just possible for the additive to remain in the part of the header tank that sits below the outlet pipe to the system. If you have to add in the header tank it's advised to make up a hose the will poke down the outlet pipe and pour the stuff there so you know it's all in the right place. Reply to this message | Report message

Fri 10 Dec 10 10:16   Draining down & flushing a central heating system. - Dog

>>n that case worth doing the interim refill and run for 24hrs before final drain to make a better job of flushing the cleaner chemical/crud<< Thanks - I'll do that then. >>If you have to add in the header tank it's advised to make up a hose the will poke down the outlet pipe and pour the stuff there so you know it's all in the right place<< Yes, what I did with the X400 was to use a syphon to get as much water out of the outlet pipe as I could before adding the agent. Reply to this message | Report message

Fri 10 Dec 10 12:04   Draining down & flushing a central heating system. - Cockle

>> Aha - I'm thinking of a partial drain (upstairs only) this morning to replace a >> stuck TRV. Not something I've done before but seems silly to pay someone to do >> what should be a relatively simple task. Will keep an eye on this thread. Plumber friend showed me a little trick some time back that he uses when changing valves, he can do one in under 20 minutes without draining down. It requires two corks/bungs and a bit of faith. His theory is that for water to flow from a pipe, or any receptacle, there needs to be two openings, if there is only one then water will not flow; as demonstrated by the old trick of putting a straw in water placing a finger over one end and pulling out the straw containing the water, for the water to flow it would create a vacuum but nature abhors a vacuum thus water will not flow. Principle is identical to that used by laboratory workers using a pipette to transfer fluids from one tube to another. Therefore he reasons that if you can seal all outlets to a central heating system then you can happily open up the system at one point without the system draining out thus enabling the changing of a rad valve without draining down the system. He uses two conical bungs and puts one in the end of the expansion pipe over the header tank and the other in the outlet pipe from the header tank to the system - system now sealed. When you open up the pipework where you want to work you will normally get between half to a pint of water flow until the vacuum kick in, after that very little. You can then work without the time consuming job of a drain down. Suggest you give it a try, you should be able to tell if it's working just by opening the valve over a bowl. He used this method when putting in a new bathroom radiator for me, did all the towel rail pipework first and the just cut into the flow and return pipes in turn, removed the bungs opened up the valves and bled the towel rail, all done in no time. If changing a radiator valve I would always take the radiator off the wall anyway and give it a good flush through with the garden hose - outside, of course!! Reply to this message | Report message       1

Fri 10 Dec 10 12:32   Draining down & flushing a central heating system. - bathtub tom

>>He uses two conical bungs There's an item I haven't seen for yonks. It's a series of (cork?) cones, joined together, that's used by chippies to get a neat finish on countersunk screws. The idea is, you put the screw-head in really deep and then put a countersink bit in to open the hole above. The 'conical bung' goes into the countersunk hole and is cut off flush. Perfect for temporarily blocking the outlet in a water tank. Reply to this message | Report message

Fri 10 Dec 10 12:49   Draining down & flushing a central heating system. - smokie

Now you mention it I remember seeing a plumber do the same on my system. Unfortunately the tip came too late and the job is done. I've put some x400 sludge remover in the system which is suppose to clear it out a bit then after another empty I have a bottle of x100 to put in. Reply to this message | Report message

Fri 10 Dec 10 15:13   Draining down & flushing a central heating system. - L'escargot

>> Aha - I'm thinking of a partial drain (upstairs only) this morning to replace a >> stuck TRV. Not something I've done before ......... TRVs have a habit of getting stuck when the system is idle. Have you tried unscrewing the thermostat part and then moving the valve pin up and down to free it off? Reply to this message | Report message

Fri 10 Dec 10 19:13   Draining down & flushing a central heating system. - smokie

Yeah, tried that L'es. All is well with new TRV but I now have two rads not warming up. Probably some balancing required in the system, or an airlock maybe? I turned off all except those two and they warmed up. Reply to this message | Report message

Fri 10 Dec 10 09:57   Draining down & flushing a central heating system. - henry k

>>None of my 10 rads have got a drain orf point so I'm a'gonna just go for the lowest rad and fix a hose pipe or something to it somehow. >> I do not know what the offcial way is of disposing of the gungy fluid that you have extract :-( I would extract it from the nearest radiator to an outside door. No idea how you are going to get a hosepipe attached. I have always used a very old grill pan to initially catch the fluid and then decanted it into a bucket but that was only for individual radiators. ( the system I inherited has two drain cocks emerging from ground floor outside onto my patio. Once the system is drained have you considered doing any further tasks like:- Changing the ball cock washer, putting a drain cock in ( ready for 11 years hence) or even lifting off radiators and giving them a good flush through. Do check all radiators carefully after you refill as that is when pinholes seem to appear. Reply to this message | Report message

Fri 10 Dec 10 10:08   Draining down & flushing a central heating system. - Dog

>>Once the system is drained have you considered doing any further tasks like:-<< The thing is Henry - the house is up for sale and The Reverend and Mrs Smith are coming to view it on Tuesday (seriously) so any new occupant is likely to stick in a condensing jobbie anyway. Reply to this message | Report message

Fri 10 Dec 10 09:59   Draining down & flushing a central heating system. - CGNorwich

Not sure how you are going to fit a hose to the rad without a drain point. i think you are going to have to undo the valve joint and let the water run into a bowl, when bowl full tighten up valve and repeat until system empty. Make sure you have plenty of old towels handy! When you have drained the system make sure you fit a valve with drain point to at least one of the downstairs radiators so you don't have this problem in future Reply to this message | Report message

Fri 10 Dec 10 10:10   Draining down & flushing a central heating system. - Dog

The 21st Century and we are still heating water by fossil fuel and pumping it around the house to rads :( Reply to this message | Report message

Fri 10 Dec 10 18:46   Draining down & flushing a central heating system. - corax

>> The 21st Century and we are still heating water by fossil fuel and pumping it >> around the house to rads :( You could always design and build your new house with mega insulation, geothermal heating, south facing conservatory with heat pump, triple glazing, roof mounted solar heating and solar panels and reed bed sewage system *, but you'd need to have a few quid and appear on Grand Designs.. * Have I left anything out? :) Reply to this message | Report message

Fri 10 Dec 10 10:14   Draining down & flushing a central heating system. - sherlock47

I think that you wil find that a Hozelock (screw on ) Tap adaptor will fit the the thread on the radiator valve. You can then just plug on a hose when needed. It will only leave you with the contents of the chosen radiator to deal with using bucket and pan. I have several radiator valves Teed of drop pipes dedicated to this purpose. I am not sure I would start this at a time of year when you would like to have the system operational. I have just deferred adding a radiator for this very reason. I have in the past semi back flushed the system using mains pressure water and careful manipulation of radiator valves - just make sure that you do not overflow the header tank! if you cannot turn off the feed. There is the ever present problem of removing crud and openiong up pin hole leaks. Reply to this message | Report message

Fri 10 Dec 10 10:21   Draining down & flushing a central heating system. - Fenlander

>>>There is the ever present problem of removing crud and openiong up pin hole leaks. Good point. We've replaced 8 of our rads over the past year or two... 6 were changed due to differing heat requirements from when the system was first put in but 2 were due to pinholes that appeared after the multiple drain downs this work entailed. Reply to this message | Report message

Fri 10 Dec 10 10:21   Draining down & flushing a central heating system. - Dog

>>I think that you wil find that a Hozelock (screw on ) Tap adaptor will fit the the thread on the radiator valve<< Good man - I'll check that out. I have to do the job now pmh, as I have the X400 in the system and all the crud is in suspenders as it were - at least its warmed up now anyway (for the time being!) Re: pin hole leaks ... you must have seen my water cylinder then :( If the worst come to the worst - I'll buy a multi-fuel stove :) Reply to this message | Report message

Fri 10 Dec 10 10:34   Draining down & flushing a central heating system. - Zero

If i was selling the house I wouldnt bother, If the system is providing warm water to rads at the moment I would just make sure it was turned on some time prior to a new purchasers arrival. Reply to this message | Report message

Fri 10 Dec 10 10:40   Draining down & flushing a central heating system. - Dog

>>If i was selling the house I wouldnt bother,<< Yeah, same here but - you know how it goes, first the pump, then the blockage in the header tank, I'm up for it now though - didn't even know what a fill and expand tank was until a few weeks ago! Reply to this message | Report message

Fri 10 Dec 10 10:47   Draining down & flushing a central heating system. - Iffy

...If i was selling the house I wouldnt bother... Good look with punting the house to the man of the cloth. But if he don't buy it, or even if he does, chances are you'll still be living there for another two or three months, at the coldest time of the year. You need the heating/hot water to be working satisfactorily. Reply to this message | Report message

Fri 10 Dec 10 10:47   Draining down & flushing a central heating system. - Dulwich Estate

A point of interest: Our system was flushed through by a plumber friend who presumably knew how to do a proper job. He had a fancy pump and by opening and closing the rad valves he flushed each radiator individually - he said that was the only way to do it properly. It took most of the day. Reply to this message | Report message

Fri 10 Dec 10 10:49   Draining down & flushing a central heating system. - Iffy

...It took most of the day... A plumber, most of the day, in London? Wouldn't want to pay that bill. I know Dog's in Cornwall, but no wonder he's trying to do it himself. Reply to this message | Report message

Fri 10 Dec 10 10:52   Draining down & flushing a central heating system. - Dog

>>He had a fancy pump and by opening and closing the rad valves he flushed each radiator individually<< Was it something like this D/E ~ www.pflush.com/how-we-power-flush.html Reply to this message | Report message

Fri 10 Dec 10 10:58   Draining down & flushing a central heating system. - Bromptonaut

A timely thread. Started having probs about three week ago with boiler getting noisy and cutting out. Team Baxi came and 'sorted' it by replacing a pump control panel. All OK for a week or so then more noise and eventually boiler cuts out on overheat. I'd had a suspicion about the F&E tank and have this morning drained several pints of water from the drain point with no corresponding movement in the F&E so it looks like a blockage somewhere. Don't have time skills to mess myself & have found a local plumber (if he's as young as he sounds the wife probably taught him!!) Reply to this message | Report message

Fri 10 Dec 10 10:48   Draining down & flushing a central heating system. - bathtub tom

I'm with Zero, let it be an SEP. I had every radiator off a few years ago and flushed them through outside, the crud that came out was unbelievable. In-laws place used to be cold because the rads only got lukewarm at the top. They wouldn't believe me that it was crud. The family were convinced they just needed bleeding, which didn't work of course. They eventually called a plumber but baulked at the price. In the end they let me take one rad off and flush it through and then I had to do the rest! Reply to this message | Report message

Fri 10 Dec 10 10:54   Draining down & flushing a central heating system. - Dog

I wonder how many people check the inhibitor strength Looseat - on a yearly basis, like. Reply to this message | Report message

Fri 10 Dec 10 11:27   Draining down & flushing a central heating system. - Dulwich Estate

Was it something like this D/E ~ www.pflush.com/how-we-power-flush.html Yes, Dog -pretty much the same as I recall. I know the bloke well, through my business at the time, so it didn't cost much. He set it up and then got on with other things as each rad took maybe 20 minutes or so to do. You could check the cleanliness of the water in the pump reservoir. If I were to do it myself sometime I'd try and hire the pump. Reply to this message | Report message

Fri 10 Dec 10 11:31   Draining down & flushing a central heating system. - Dog

>>If I were to do it myself sometime I'd try and hire the pump<< Cheers D/E - if I'm still here in the Summer, I'll hire one and do the job properly. Reply to this message | Report message

Fri 10 Dec 10 15:21   Draining down & flushing a central heating system. - Mapmaker

Powerflushing is a very dull way to spend a day (I am told) and is done just as DE describes. In order to facilitate removal of radiators etc. etc. I don't bother with two bungs, instead I have two taps which I can turn on and off at will. Reply to this message | Report message

Fri 10 Dec 10 15:35   Draining down & flushing a central heating system. - sherlock47

>>>>In order to facilitate removal of radiators etc. etc. I don't bother with two bungs, instead I have two taps which I can turn on and off at will.<<<< I hope that you do not have a tap on the expansion pipe! Or you wear a flak jacket and head protection. You may know (or thinkyou know) what you are turning on or off but what about any future owner? Reply to this message | Report message

Fri 10 Dec 10 15:38   Draining down & flushing a central heating system. - Mapmaker

>>I hope that you do not have a tap on the expansion pipe! Of course... otherwise it wouldn't work. >>what you are turning on or off but what about any future owner? I'm not leaving spare taps behind when I move out. Do you think I'm made of money or something? Reply to this message | Report message

Fri 10 Dec 10 15:48   Draining down & flushing a central heating system. - sherlock47

>>>'m not leaving spare taps behind when I move out. Do you think I'm made of money or something?<<< But somebody else may copy what you have done and not be so tightfisted! At worst you should fit a pressure relief valve. Reply to this message | Report message

Fri 10 Dec 10 15:18   Draining down & flushing a central heating system. - L'escargot

>> None of my 10 rads have got a drain orf point so I'm a'gonna just >> go for the lowest rad and fix a hose pipe or something to it somehow. It sounds as if you think all your radiators are is series. Are they? Reply to this message | Report message

Fri 10 Dec 10 15:51   Draining down & flushing a central heating system. - Zero

It matters not, the water will drain from the lowest point if they are all open. Reply to this message | Report message

Fri 10 Dec 10 16:46   Draining down & flushing a central heating system. - Dog

>>It sounds as if you think all your radiators are is series. Are they?<< I don't really know L'es, but I presume they are - I'm going to make a start (tomorrow) by closing the valves on my lowest rad, which is in the conservatory, drain that critter into bowls like I do when I'm removing a rad for decorating, then I'll see if a garden hose connector will fit the valve so as to drain the system - I can always whiz down to Plumb base and buy a valve with a drain tap if need be. Reply to this message | Report message

Fri 10 Dec 10 17:39   Draining down & flushing a central heating system. - FotheringtonTomas

You'do much, much better removing the radiators, taking them outside, and then flushing them out. Reply to this message | Report message

Fri 10 Dec 10 17:42   Draining down & flushing a central heating system. - Dog

>>You'do much, much better removing the radiators, taking them outside, and then flushing them out<< Yes, I realise that F/T but - its going to turn cold again by Monday so I'll jsut drain & flush it for now. Reply to this message | Report message

Fri 10 Dec 10 18:04   Draining down & flushing a central heating system. - FotheringtonTomas

>> its going to turn cold again by Monday so I'll jsut drain & flush it for now It's probably pointless work. If the system is at least moderately functional, leave it until you can do a proper job. Reply to this message | Report message

Fri 10 Dec 10 17:43   Draining down & flushing a central heating system. - Zero

>> You'do much, much better removing the radiators, taking them outside, and then flushing them out. Yup, hard work but does a much better job than the flushing tool, and cheaper too. Reply to this message | Report message

Fri 10 Dec 10 17:53   Draining down & flushing a central heating system. - Dog

As I say further up - the house is se vende, but if we're still here next Summer I'll have the cylinder replaced and clean out all the rads (10 of em!) in prep for a new condensing broiler. Reply to this message | Report message

Mon 13 Dec 10 10:29   Draining down & flushing a central heating system. - Dog

Update ... I removed rad in conservatory, stuck a 1" plastic pipe on the valve and drained system into convenient outside drain. Plenty of mess but tiled floor :) Refilled system, ran it for 6 hours, and drained it again. Flushed system with all the bleed screws on the 10 rads removed. Wife running around like a headless chicken cos of fountains from all rads :-D Refilled system, added X100 inhibitor, bled system twice - jobs a good'n. Reply to this message | Report message