System draining / flushing

[mcb7]

I'm fairly certain the CH system at my girlfriend's house is in dire need of flushing because this last winter the system was very slow to heat the house up and all the rads on the ground floor had very sooty water when I bled them, upstairs ones not so much. The pump was also making more noise than I remember in previous years. The house is a 4 bed detached built about 25-30yrs ago and the CH system is an open vented one.

So firstly, would you agree the system needs flushing? If so my second question is about draining the system: I can't find any obvious system drain point, there are suitable drain cocks on the in and outlet to the boiler but they are at ceiling height on the ground floor so presumably would only allow the upstairs to be drained. Unless there's a drain cock behind a wall or under the floor boards, the only thing I've noticed is that all the rads on the ground floor have a connector as shown on the attached picture. It has a square valve like a bleed screw inside so I'm guessing you can open it up with a bleed key and then stick a tube on it, it sounds like a bit of a pain to have to go round each rad though. Any thoughts on whether this was the intention of the installer?


Last question: if I decided it was too much to take on myself, what sort of ballpark price am I looking at to get someone in to flush the system?
Ta.

 

[oldbuffer]

1. The "connector" shown in your picture is a drain off point. As you say, slacken square headed screw, quickly attach hose and drain. I hate these, as the only way to get the to drain quickly is to remove the screw, which usually result in water everywhere, and the loss of the screw.
2. Unless the downstairs radiators (one or more of them) are fed by dropped pipes from upstairs, you only need to drain the whole system through one drain off point. Any which are fed from drops will need to be drained separately.
3. Assuming 8 to 10 radiators I'd expect to take a good working day to flush a system like your girlfriends using a proper flushing machine and the right chemicals, and testing the system water at the end.

 

[mcb7]

Thanks @oldbuffer, there's 17 rads in the system so I'd imagine that would put the price up a bit. Found a local company that says it would be around £350 for up to 10 rads then £30 for each extra, so £560 in total, I'm guessing that's about an average price. Presumably, if I have time on my hands I could do a more manual flushing approach but that might mean removing rads if they are particularly blocked up?

 

[Scarum]

Draining from the radiator valve should be easy.

1. With rad in question, close both valves fully, if one of them is a TRV it may not close 100% (you'll find out at step 2 or 3). If this is the case you can get TRV caps that screw on to the valve body that fully closes them.
2. Open bleed valve at top of rad (this creates a vacuum) then close bleed valve
3. Remove drain-off screw shown in your photo, a little water may come out so have an old towel or bucket at ready
4. Attach hose securely and set to drain to outside drain
5. Open both radiator valves to drain system

Before doing all this you might want to bale out the feed and expansion tank in the loft so it doesn't introduce potential crud in to the system.