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See the quick fix below Click here.
The problem
Limescale is often deposited at the junction of the cold feed pipe from the feed and expansion tank to the circulatory part of the pipework. The cold feed is usually in 15mm pipe going into 22mm pipe so is easily furred up. Water will then not fill any shortage of water in the central heating without taking a very long time. This is usually apparent after draining part of the system to fix or replace a radiator or replacing a control valve.
The power flushing chemicals cannot be directed through the cold feed pipe using the standard connections.
So whilst the main part of the system is cleaned thoroughly the cold feed pipe can still be blocked.
The solution
Connect an alternative path through the cold feed pipe for the power flushing fluid.
This is done by connecting a main adaptor to one of the power flushing machine's outlets. This adaptor has a straight through full bore 22mm valve for normal mode but this can be closed and a second full bore 15mm valve can be opened instead. This is connected via hosepipe to a "cold feed" adaptor which connects (using various adaptors) to the cold feed pipe.
This then allows the fluid to be directed through the cold feed pipe, dissolving the limescale in a couple of minutes.
I have made the cold feed adaptor with the facility to connect the Systemsure Injector so that fluid can be forced down the cold feed pipe under pressure. I have not yet had to use this as the power flusher has always got enough fluid through to get it going and then it clears the rest quickly.
The easiest way to connect this is to wet vacuum out the tank and cut the outlet pipe and connect to that. The pipe is repaired using a push fit or compression joint.
The cold feed pipe should be treated like a radiator i.e. flush it with FX2 added, dump clear water through it and flush again after neutralising the fluid.
Main Adaptor
The power flusher is connected to the left, the normal outlet pipe goes on the right of the 22mm full bore valve. The hosepipe goes onto the 15mm valve using the hosepipe fitting.
Cold Feed Adaptor
The hosepipe goes on the hosepipe fitting, the cold feed is connected to the push fit connector (using an adaptor if required) and the injector could be connected to the female BSP fitting.
To use the injector - close the hosepipe valve and open the isolating valve to inject a diluted FX2 solution. Then close the isolating valve and open the full bore valve to allow the power flushing fluid to go round.
Various adaptors used to connect the feed pipe adaptor to the feed pipe itself.
Some of the adaptors - just make them up as required.
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The Quick Fix
On some installations it may not be practicable to connect the long pipe etc.
So block off both feed and vent pipes, then clean out the F&E tank - I use a wet vacuum cleaner.
Then circulate the acid solution using the power flusher in normal mode, ensuring that it goes round near the entry point. This is usually near the DHW tank pipes.
Make sure the water level in the power flusher is near the max then switch it off and close the valves to avoid the water coming back into the unit. Next remove the plug on the cold feed pipe, go back to the power flusher and switch it on and open the valve on the flow side only. This will increase the pressure in the system to about 1 bar which would normally be enough to force some acid solution up the feed pipe and into the tank. There should not be enough to cause it to overflow. You will see the fluid level drop in the power flusher; when it gets low but not quite to the minimum level switch off the power flushing machine, leaving the valve open. The fluid should then drain back into the machine.
This has caused an acid solution to go through the blocked area and will have dissolved some of the limescale. Switch the power flusher on again and repeat this sequence several times to clear the pipe.
Allow the level to go up again to minimise the fluid in the F&E tank.
Close the valve again. Remove the acidic water from the tank and fill it from the supply.
Open the valve again to let some clean water back down the feed pipe. Block the feed pipe and carry on flushing as normal. When it comes to rinsing with fresh water let more come down through the feed pipe again to ensure it is clear of acid then seal it again for the rest of the flushing process.
I prefer to flush this pipe using the adaptors etc as it will give a better clean and the rinsing is more easily effected but this does work too.
All oil fired plumbing and central heating repairs undertaken.
Contact Details
Tel: 01258 45 86 85 or e-mail me at service@ariesplumbing.co.uk