CH piping issue, block in cold feed pipe

[mayurw]

I'm hoping somebody can help me with a problem my friend is having with his heating system - see diagram below.

In the last 2yrs I've helped him get his heating working and as the issues seems to be the same, I thought I would put the question out to see if this can be prevented again.

The pipe coming down from the feeder tank is getting blocked which is causing the pump to run dry but why is it getting blocked? when this happened the first time, I thought it was crap in the feeder tank and we cleaned it out but when this happened yesterday again but the tank was clean. We removed the pipe going down to the pump and there was a blockage of some brown stuff which I had to force out using a wire hanger.

The flow from the boiler runs up and then its tee'd into the pipe running down from the feeder tank as shown, I assume the reason the flow pipe continues running up into the loft is for venting purposes? should the flow not go directly into the pump?

Once we got the heating working yesterday I checked the pipes and both flow vent (after the tee, water is flowing up) and feeder pipe (above the tee, water is flowing down) were getting hot.

Any ideas?, I hope this make sense

 

[mayurw]

View media item 58588

 

[Whitespirit66]

The cold feed is notorius for blocking where it tees into the system pipes. It's magnetite - magnetic debris from corrosion in the system - mainly rads.

Make sure the blockage is completely cleared, put some system cleaner in, run system for couple of weeks, drain, flush with water, then refill with water and corrosion inhibitor.

Keeping corrosion inhibitor in the system and making sure that the vent pipe over F&E tank isn't pumping over will help to ensure that corrosion is kept to a minimum.

Also consider a system filter, eg -

http://www.fernox.com/equipment/filters/total+filter+tf1

 

[Onetap]

The only reason the cold feed tee will block is because there is a leak from the system and there is a constant flow of fresh water, with dissolved limescale , entering the system from the cold feed tank. The blocked tee needs to be cut out and replaced.

The system should be filled once and ( in theory) there should only be minute amounts of fresh water entering the F&E tank thereafter, to make up for evaporation from the tank. If there were no leaks, the cold feed tee is no more likely to block than any other part of the system.

The usual cause is a leak under the ground floor, a leak from the coil in the hot water cylinder, or/and the F&E tank has been incorrectly set up and is discharging water on every heat/cool cycle.