Re-filling Gravity Feed CH System

[lordspunky]

Hi, I have a back boiler gravity feed Central heating system, and with the major works I am carrying out within my house I have drained and re-filled my CH system at least 5/6 times, replaced valves & radiators and changed the route of the pipe work. Every time I try and refill the system it is a nightmare, with radiators not refilling etc.
This time I put in some cleanser for a few weeks then ditched the water and tried to refill with no luck.

Stupid question but is there a method in the refilling? I always bleed bottom to top, far to close to boiler. Right now there is a bit of hiss then nothing, no bubbling of water up the rads, need to fix this before winter!

Cheers

 

[Hugh Jaleak]

Check the cold feed from the F&E cistern isnt blocked.

 

[Whitespirit66]

Put a magnet on the tee where the cold feed from the tank joins the main pipework.

If it sticks, you probably have a blocked cold feed. Will probably need cutting out, and new section put in.

 

[lordspunky]

I did once have a blockage in the cold feed T before the pump, we cut one side of the T and rodded up the other end, but didn't replace it, will have to check (major moving required!)

 

[Whitespirit66]

Yes, they're often in a difficult to reach place. The happy world of plumbing.

However, if the tank in the loft is filling, but nothing is getting into the system. the cold feed is the first port of call.

 

[dazza87]

take a rad off downstairs make a conection for the rad so 15mm pipe will conect to rad(rad tail,nut and olive).conect hose and put main through it.very slow bleed one rad at a time and some one in the loft to keep an eye on the vent pipe.not ideal i know but needs must some times

 

[lordspunky]

stupid question, maybe, at any point should i turn the pump on? Or wait until the system is bleed? Would it damage the pump?

 

[dazza87]

it some times has a effect if you turn on full then down etc but they are a right nightmare some times i think you will find its just a air lock,fill it with a hose you will have no problems

 

[Bon]

If you're sure your system is clean, then it could be the point where the cold feed from the F&E tank connects to the system.

It's also worth double checking your pipework hasn't been moved in any way during the work you've been doing.

We had our boiler changed a while back, but I left off filling the system back up as I needed to move some rads about.

When it came to filling up the system, I couldn't do it. Long story short, when installing the boiler, our fitter had shoved the cold feed pipe upwards so it wouldn't gravity feed water into the system. I only discovered this after cutting out large sections of pipework where I thought there might be blockages!! After I'd altered the cold feed, it filled up no problems!

 

[looneyfitter]

are you sure the gate valve on the cold feed from the F-E hasnt snapped shut or the ball cock hasnt been tied up and not re- dropped?

Failing that then defenitally a blocked CF

 

[tincup]

Hi

When you drained down the system did the f/e tank drain also?
If it did it is likely to be air if not a blocked cold feed.
You could back fill it with the vent pipe.

HTH

 

[lordspunky]

There may have been an air lock before I drained it....and the expansion tank in the loft did drain with the system, I watched it myself