heating system (plumbers?)

[phil on a fazer]

Hi

Need some advice

i live in a 2 bedroom terraced house, combi bolier, 3 rads up stairs, 3 down stairs, 8mm micro bore piping.

Needed to take the living rad off as im getting the walls skimmed. I bought new valves for it (thermostate & lock sheild) so thought i will drain down the whole system, fit the new valves, refill with inhibator and bobs your uncle!  ......but not quite.........

All three down stairs rads have locksheild valves with drain valves (but my new ones dont) and the upstairs dont. So put a hose pipe on the living room one, cranked it open and water pissed out for a bit 4 seconds and that was it???? so i thought the washer may have jammed. So did the same on the hall rad....water pissed out down the hose pipe for abit 2 secs and that was it????? that cant of drained the whole system??? 

So disconnected the living rad and got about half a bucket of water out of the rad it self. The boiler is displaying zero pressure. Took the shut off cap off the thermostate valve, screwed the stat back on, opened it and closed - no water, did the same with the locksheild valve...no water.

so are the pipes drained but air holding water inside the other rads? and once ive changed the valves and fit the new ones will i have to put inhibitor inside that rad?

answers on a postcard.

Tar 

[chaz]

you need all the rad valve fully open, then open a drain off cock, when the water stops open the air bleed valves upstairs then on the down stairs rads or you could shut all the valves and leave the rads full, but the pipes wont drain off till you disconnect the valves on the one you're taking off, but with 8mm pipes there wont be that much??
you can get inhibitor that you inject into a rad by taking a bung out of the top of a rad, might be worth it in time.

[evesdad]

You can "usually" change a rad valve on a combi system without draining the whole system. Once you have let the pressure off, as long as you only have one open end (the pipe you are changing the valve on) air cant get into the system so the water cannot fall out.  Note I said usually if the auto air vent on the boiler opens or some worcester boilers with a non return valve lets in air you may get wet!

[simonm]

The water won't come out of the radiators until you open the bleed valve at the top of radiator.  Maybe I'm just teaching you to suck eggs, I don't know.

[phil on a fazer]

you need all the rad valve fully open, then open a drain off cock, when the water stops open the air bleed valves upstairs then on the down stairs rads

yeah thats it......it was a really rushed job against the clock and if i was taking my time i would of thought of that (honest!  )

So when i come to refill the system i will just open up the filler loop on the combi boiler...BUT....ive never actually used or dealt with inhibitors before. ive always thought you filled a rad with the stuff (not sure how? or how much?), refill the system and then it will be carried around the whole heating sytem.....is that right?? 

[chaz]

look on "tool station" item number 77217 £9.98 cal-shot if you spend £10 delivery is free if its too far away. not used it myself but it says goes in via rad or loop.