Problem creating a lock to change valve?

[kgreen84]

Right brought myself a bung kit, bunged the header tank and opened a vent to create a lock in the system to replace some valves on a downstairs rad (1 by 1 obviously). Problem is I got about a pint of water from the vent and got a little worried that was too much so closed it again. I opened the vents on the upstairs rads 1 by 1 and all of them had some air in but no water and eventually no air, checked the tank and definately bunged right.

So went back to the vent and reopened to be greeted with another pint of water I should I have just kept going or is this not right? The drain valve is on the return under the rad that I want to change the valves on but its so old am worried it might break and not reclose and I've not got a hose?

Sorry for waffle but got it right in my head then nearly 2 pints of water came out of the vent with no signs of stopping, should I just have kept going till it stopped or is there another problem?

 

[picasso]

did you bung the vent as well?

 

[D_Hailsham]

Do you have an automatic air vent - often on the flow to the HW cylinder? If so close it.

Open it again when finished

 

[kgreen84]

bunged both the cold feed and vent at the F+E tank

 

[assured heating]

if you close one pump valve it helps just remember to turn it back on Also some tank connectors on the F&E tank have two little bits inside the fitting that stops the bung from sealing so it will not work

 

[ollski]

I've had systems that have taken 4 or 5 gallons before the bungs hold and similarly some that just won't bung at all. Much easier to crack the rad valve than the bleed screw....takes an age. If you have an outlet with the two tabs on you can normally get away with wrapping a load of ptfe around the end of the bung, just make sure it doesn't get sucked into the system when you take the bung out!

 

[TicklyT]

..... you can normally get away with wrapping a load of ptfe around the end of the bung, just make sure it doesn't get sucked into the system when you take the bung out!

PVC / electrical tape does the job nicely - and doesn't come unravelled when you pull the bung out

 

[namsag]

Before you bung it bleed the system first, As has been said some lock straight away others can take a while

 

[kgreen84]

thanks guys - hopefully opening a return valve will sort it!