Gravity flush going to make any difference?

26 Jan 2014
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United Kingdom
Hello people

At the moment I simply can't afford to pay for a power flush and to get twin port entry valves replaced with conventional ones (Scottish Gas wont flush systems with twin port entry valves which I have 7 of) Can prob find cheaper elsewhere but they lifetime guarantee their work.

I was wondering if opening a rad on the ground floor and draining the system with a garden hose and leaving the feeder tank to flush the system for an hour or two is really going to do anything?

My plan would probably be to drain the system and leaving the feeder tank to flush the system for a few hours, refill and add some sort of inhibiter or system cleaner then repeat the process a month or so later.

I aint no plumber so was wondering if anyone could advise whether this "low pressure flushing method" is really going to do anything or will the sludge stay put until "power" flushed?

I have a back boiler that kettles like a mo fo when on HW only unless I turn the boiler stat down to 1 (Gravity fed and Scottish Gas say is being caused by the build up in the pipes. Being gravity hw I have no two port valves (none that I can see anyway)



PS had to bleed rad in bedroom and when water finally came out it was jet black for a while then ran clean
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Unfortunately although you will wash some of the crap out there will still be loads remaining just where you don't want it.......a better diy job is to remove each radiator in turn and flush them out with the hose - allowing the tank supply to wash through each supply pipe in turn as you go.
John :)
Thanks for the replies thus far

As I suspected, it's never going to be as good as the real thing. I was quoted over a grand to get the rad valves changed, powerflushed and the HW changed to fully pumped.

A concern I have about doing it diy style is the possibility of a blockage occurring in the 10mm microbore pipework I have in the house if I do it, at which point it would be panic stations and get the wallet ready.

The majority of the rads in this house are approx. 35 years old and part of me thinks I should just bite the bullet and start saving for a full new system.

Would you recon 35 year old 10mm microbore would be ok to reuse with a new boiler and rads or would it be best for the whole lot to be replaced?


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if you can do simple plumbing and can afford £100 or so, fit a system filter which will trap circulating particles and prevent blockages and sediment getting worse.

if you do fit a filter, you can then add a permanent product such as Sentinel X900 which will encourage sediment to loosen and flow round, so the filter can trap it.

you can also add, and leave in, X200 which will soften and dissolve limescale deposits from the boiler, which are often responsible for kettling. But do the sludge clean first.
Power flushing the boiler and central heating system involves emptying your system of existing dirty sludge-filled water and filling it with clean water and if required, a rust inhibitor is also added. The heating system is connected to a pressurised pump that works loose the rust and as the sludge is removed from the radiators and boiler it is collected in a filter. The complete process takes hours for a typical house or apartment.

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