Central Heating System - possible blockage - how to fix?

[Walkleyboy]

Hello,

My central heating system has been running OK for the past few years, but yesterday things went wrong.

The system is a 1980's vintage gravity fed system.

The problem started as follows:

1 - I'd noticed that a couple of rads were slightly cool, but warmer at the bottom than the top.

2 - Switched off the pump and bled the rads. A lot of air came out, but they did bleed OK. Re-sealed the bleed valves.

3 - Switched back on assuming all would be OK and went out to collect the wife (shopping)

4 - Got back and all the rads were cold. Checked the room thermostat and boiler timer, both OK and demanding heat from the boiler.

5 - Checked the boiler pilot light and that it fired 'on demand'. All OK.

6 - Took a look upstairs at the pump. This was hot and didn't sound like it was pumping water. Switched the pump off.

7 - Checked the CH header tank. This was OK and the ball value worked OK.

8 - Tried to bleed the pump. Pump was dry (as suspected)

9 - Removed the cap from the system air bleed-cap and 'dipped' the pipe with a knitting needle - also dry (that's more than a foot).

10 - split the header tank feed pipe just above the circuit - all OK water flowing.

In summary, I seem to have water on one side of the pump, but not the other, and attempting to bleed the system via the bleed nipple isn't working.

I'd really appreciate any advice re the next steps I should take.

Thanks in advance,

Chris

 

[oz-plumber]

If the pump was hot and was not pumping, it sounds like a faulty pump.
When you bled the pump, was the shaft spinning?
Put a mall screwdriver in the pump shaft and see if the spindle is free.
If not, time to replace pump

 

[SimonG]

Pump could be goosed or an air lock. Went to one last night. They had drained system and refilled, but airlocked. Try cracking a nut on the pump valve with a towel round it. Could also be a blocked cold feed as it tees in. When you bled the rads you could have lowered water height in system.

I would take it in order of airlock, blocked feed then pump. But doubtful on pump unless its been running dry for too long.

 

[Walkleyboy]

Thanks to oz-plumber and SimonG for the replies. Things have moved on a bit...

Closed the lock shield valves on both sides of the pump, then opened up one side of the pump connectors. That means that there's no water on either side of the pump and therefore no feed from the headertank.

If there is a blockage, then it has to be below where I split the header feed last night, but above the tee into the pump circuit...

Looks like SimonG may be right!

Thanks again

Chris

 

[Walkleyboy]

Nailed it - blocked header tank feed just above the entry to the circuit as suggested by SimonG. Must have been about a centimetre of solidified gunk.

Now to put it all back together...

Thanks to all

Chris

 

[Best]

The feed pipe usually blocks at the tee and just below it.
You bleeding a radiator just made an already low in water system worse.

 

[Walkleyboy]

System is back together and running. We are all nice and warm once again.

When I split the header tank feed last night, I did rod it with a bit of twin and earth flex. I should have looked more closely at how much I used - it seemed to be near enough to the right length to the tee joint and I hadn't recognised just how hard the blockage actually was.

In my defence it was half eleven!

FWIW I did check how much this would have cost if I'd called out British Gas - £408 plus VAT if they took over four hours!

Ignoring my time, it actually cost about a tenner

Thanks to those who offered advice freely - you can begin to get an idea of just how much it was really worth!!!

Chris

 

[SimonG]

Thanks for coming back and letting us know

 

[Rickster123]

System is back together and running. We are all nice and warm once again.

When I split the header tank feed last night, I did rod it with a bit of twin and earth flex. I should have looked more closely at how much I used - it seemed to be near enough to the right length to the tee joint and I hadn't recognised just how hard the blockage actually was.

In my defence it was half eleven!

FWIW I did check how much this would have cost if I'd called out British Gas - £408 plus VAT if they took over four hours!

Ignoring my time, it actually cost about a tenner

Thanks to those who offered advice freely - you can begin to get an idea of just how much it was really worth!!!

Chris

Send SimonG a cheque for £407+vat... Or £400 for cash! :wink5:

 

[turnpin]

Agree with Simon G ....always good to get feedback especially good feedback thanks ....oh and welcome to the forum's..regards Turnpin:8: