flushing central heating

[jonnyboy31]

i live in a ground floor flat and have a worcester bosch combi boiler. had noticed that some of the radiators had very large cold patches in the middle. was going to individually remove all radiators and flush them through with a hose pipe but instead got some fernow cleaner and added that to the system and have left it a week. all radiators now work properly which i am extremely happy with but now need to drain the system. problem being there is no drain valve any where in the system that i have been able to find, so i have bought one and am going to fit it once the system has been drained. can any one tell me the best way to drain the system, and once the system has been drained the best way to flush the system. i am inexperienced with plumbing and am not keen on cutting pipes. was hoping to be able to drain and remove a radiator then attach a hose pipe to one of the valves and flush the system through with the tap i use to re presureise the system is this possible? am hoping to do the job tomorrow.

cheers for any advice

jon king

 

[rebuke]

I would be very surprised if there wasn't a drain valve anywhere - have you tried looking outside (front and back), as it might be it appears there from underneath the floor (has to be at the lowest point obviously)?

If not, then the only thing I could think would be to do something like:
Turn off one radiator at both ends
Get a large bucket (or several!) ready
With an ice cream tub or similar underneath, carefully undo the connector at one end of the radiator (water will come out), once it starts, open the bleed valve on the radiator to help it
Remove the radiator
Using ice cream tub / bucket if it fits or a cunning hose fitting if you can find one, drain the system through the outlet

It's definitely not ideal, as it will probably take a long time, and you'll be left with water below the point you drain it at (i.e. probably in wherever you're going to fit the drain valve!), but might work...

(Disclaimer: I'm not a plumber, so don't take this advice as gospel...)

 

[Goldspoon]

Turn boiler off (ideally at fused spur). Do not use boiler at all if no water in CH circuit.

If you can find a drain point: Fix hosepipe to a drain pipe on one of the downstairs rads (or might be a drain off point near boiler) and drain off an amount of water to outside drain or garden (you'll see combi boiler pressure drop from whatever it is, likely between 1 bar and 2 bar... eventually to zero). Keep draining until you have emptied the rads (you will need to open the rad air bleed screws - starting at the top of the house and gradually working down - to allow air in, which in turn allows water out the hosepipe - essentially you are getting rid of a vaccum that would otherwise prevent draining). Take care that you are not just draining a "drop down leg of pipework" - this is okay but don't then go and work somewhere else thinking everywhere is empty.

If no visible drain point then you'll just have to choose a low radiator and close both the TRV (switch it to off or lowest setting) and lock shield valve (this then means that the rad is cut off from the circuit). Then carefully drain the ONE rad only by loosening the connection between the rad and the lockshield valve and letting the water flow into a paint tray or something suitable (open bleed valve on rad to allow air in). Be ready to tighten connection as water fills paint tray as rads hold a lot. When rad is empty you can then think about rest of water in circuit (under pressure still!). Obviously if you now open the lock shield valve or the TRV then water will spurt out... what can you insert or attach to this? For example on the TRV next to my desk now I could insert 15mm pipe (inc. olive and nut from a 15mm iso valve or compression fitting) into the TRV, tighten it up and then attach hose to that with a jubilee clip... then switch on TRV and water will be off and away. If it’s a big thread then a wash machine hose will likely fit with other end connected to some plastic 15mm pipe (or tucked into some waste pipe and fed outside). It’s just about getting the water out and diverting to a drain or garden.

TOP TIP: If a rad is taken out but the flow and return still pressurised then be aware a TRV can open if the temperature in the room drops enough due to frost setting sort of thing..

When re-filling you do this using the combi boiler filling loop (boiler still off). Google some pics to see what one looks like. Stop at 1 bar pressure and then bleed downstairs rads (so water filling from bottom of house upwards)... pressure will drop so top up to 1 bar and bleed again and continue this bleeding all rads inc. upstairs. When no air in all rads pressure up the system to what it should be (likely 1 bar to 2 bar - check your boiler manual). You should add some inhibitor (early in this process - add inhibitor whilst drained down, either via pipework at TRV or by taking bleed valve out and putting in top of rad)..

I add inhibitor via a rad: take out the top bung (like the air bleed screw but just a blank). Insert one end of a 15mm iso valve and gently tighten. On other end of iso valve is small length of copper pipe connected to small length of hose and then funnel. Pour inhibitor into funnel which then flows thru hose and past iso valve into rad (make sure iso valve open lol). You may need to open opposite air bleed valve to allow air to escape as inhibitor enters. One can add inhibitor like this at any time - just drain down some water, add inhibitor to a upstairs rad, then refill.

I am not a CH expert ... I'm sure somebody will chip in if I am wrong or have missed anything.

 

[jonnyboy31]

cheers for the advice, if there is a bleed valve under the floor i won't have access as my whole flat has laminate flooring and i think if i pull it up then it wont go back down.
think i have an attachment that will fit one of the valves once i have removed a radiator just need to no which end to attach it to then how to flush the system, was going to try using the same thing that i use to re pressurize the system

 

[wiggikins]

Why not just get a self cutting D.O.C. .............a lot easier than all that hassle ............then chop it out on completion and fit a type"A" D.O.C......SIMPLE.

 

[jonnyboy31]

what is a D.O.C?
was thinking of adding in two drain points on both the pipes going in and out of the boiler, but don't no how to cut pipes which are atached to the wall? or cut pipes in general!!

 

[wiggikins]

D.O.C.=Drain off cock

1) Junior hacksaw
2)Pipeslice,(purpose made tool,available most merchants).

 

[Goldspoon]

Your last post makes no sense? You just state what a DOC is and then list two tools...

 

[wiggikins]

Makes perfect sense to me .........or did you see something in the O.P's question that i didn't

 

[Goldspoon]

Apologies - somehow I missed a post.

 

[jonnyboy31]

cheers for the advice managed to do it and added a radiator valve with a drain off point in it. just had trouble adding the fernox protector afterwards. did exactaly as it said but it just fired fernox all over my kitchen which made a mess and wasted £30 on the fernox!!