water not flowing through pump


Postby gumbo » Sat Dec 08, 2007 11:52 pm

ive just replaced my central heating pump due to the downstairs rads not heating up. I drained down the system, fitted the new pump with the arrow in the same direction as the old one (pointing down), turned the water back on and started to bleed the system starting downstairs. All that bleeds out is a small amount of air but no water, tried bleeding the pump following the instructions and still no joy. I decided to disconect the pipework just below the pump to see if any water is passing through and there wasnt. Even when turning the pump on all i get is a trickle of dirty water. The pump valves are open and the pump is a smart wilo, please help.
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Postby marrtin » Sun Dec 09, 2007 11:14 am

Seems as if your system is not filling. You have checked that the header tank is full of water? If so, possibly the feed pipe is silted up. Use a plunger to remove anything blocking the pipe.
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Postby gumbo » Sun Dec 09, 2007 1:02 pm

ive left the system over night with the pump off and after bleeding the downstairs rads again they are finally bleeding out water as are most of the upstairs rads but not all of them. turned the pump on and it sounded like there was lots of air in the pipes so bleeded the pump again and this time i got a trickle of water from the bleed hole. done that a few times then left it running. boiler came on for a while then turned off, boier is hot to the touch so i asume its working but i still have no heat from the rads. downstairs rads are still bleeding water, uptairs rads a mixture of water and air, some rads just air then nothing. i've checked the header tank and although full of crap at the bottom the outlet seems clear.
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Postby marrtin » Sun Dec 09, 2007 2:42 pm

Your new post confirms my suspicion that the feed to the heating is partially blocked. The exit from the tank that you can see may be clear, but often is the case the pipe further down is filled with sludge reducing the flow to a trickle. Hence your system filling partially overnight.

Pump a plunger over the pipe, or use a hosepipe to force water into the feed pipe to clear the sludge.

Also, if you have a motorised valve, make sure it is open.
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Postby gumbo » Mon Dec 10, 2007 6:54 am

thanks for the help, you was right the feed to the heating system was blocked at the T junction where the return feed joins the supply pipe via the air seperator. The hose pipe and plunger wouldnt clear it as i suspect its been blocked for some time (ive only just moved into the house). Ended up cutting the pipe just above the T junction and ramming a screw driver down the pipe which after a while cleared the blockage. Will repair the pipe later and refill the system, fingers crossed all goes well. What would you recommend in the way of a system flush and prevention?
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Postby marrtin » Mon Dec 10, 2007 8:44 pm

It has probably taken ten years for the build up, so just get some sludge remover (any brand will do), follow with some inhibitor. Just follow instructions.
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Postby gumbo » Tue Dec 11, 2007 8:00 am

Thanks again for your help, all went well with the refill and rads are now piping hot. Thinking of replacing the rad valves with trv's, is this just a simple swap as i've heard you need to add a bypass or something when fitting trv's?
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