Draining sealed system to fit new raditor valve.

[Tomdawn]

Hey, I need to drain my sealed system is a combi boiler. As I need to change one raditor valve as it is corrded. Do I need to drain the whole system including venting all the raditors to do this? Thank you for any advice I want to try and avoid any air locks if possible,

 

[plumberdan]

Get a plumber in shouldn't cost that much £10.00 for valve and at the most 2 hours work max at £20.00p/h. Alternative, find the lowest point on the system to drain from, turn off boiler, open drain valve, after 5mins open bleed taps on radiators on top floor then 10mins later move down a floor, and so on, depending on how the system was piped the ground floor rads may or may not drain depending on whether the pipes come down from upstairs(drops) or up from the floor! Once drained change valve, then go round closing all bleed taps on radiators, and drain valve, then pressurise boiler to 1.5 bar and bleed ground floors rads till full then move up a floor, nipping back to boiler when the pressure has gone(cant hear the air hissing through the bleed valve) all radiator valves must be open before draining system! Turn Central heating on leave 30mins, re-check rads for air, re-check pressure top up to 1.5 bar no more!

 

[nickso]

why drain everything to change one TRV?

take the pressure off at the boiler or a drain point. drain the rad and the pipe the TRV is on into a dish under the rad. Normally you get less than half a bucket of water out, takes no time at all and means you introduce far less air back into the system to corrode everything.

 

[plumberdan]

If the auto air vent in the boiler opens to vent, all the water above the pipe may be released causing a bit of a mess, just draining the rad relies on an air lock keeping the rest of the system water where it is if air lock fails, then you'll get wet! Also forgot to mention you'll need to add a bottle of Central heating corrosion inhibitor to protect the system before refilling! As a time served plumber I would drain the rad whip the valve off and replace in 10mins, as a diy'er I take the safe option to eliminate potential problems!

 

[nickso]

But draining the entire system is not eliminating all potential problems.

DIY or not this bloke has to decide on whether to faff about draining and refilling an entire system (which admittedly is a sealed system and 99 times will be simplicity itself) or draining only the components he needs to change. I have to admit to being lazy and I never check if there are any air leaks above the component to be changed. Guess how many times I have had a problem with the probably several thousand times I have done it that way.

I am not advocating he snatches it by the way, I rarely do, merely that he doesn't waste his time draining the lot.

 

[misterdubya]

Its a sealed system. Release the pressure as nickso has said. Why drain it all, and loose the inhibitor? - oh and waste time draining and re-filling with new inhibitor.

 

[sooey]

Get a plumber in shouldn't cost that much £10.00 for valve and at the most 2 hours work max at £20.00p/h.

You're working too cheap pal. £20.00 an hour

 

[plumberdan]

It might not have inhibitor in at the moment!!! Or might need topping up, that stuff doesn't last forever! I was merely giving the man some options, well I work for a company, that's just what I say for the govy's! Cheap price repeat work, a way to build customer base for my own company!

 

[sooey]

Cheap price repeat work, a way to build customer base for my own company!

A customer base that will expect ridiculously cheap prices in the future!!
See how long you can work for those prices when you do have your own company. It's guys like you who are forking things up for everyone else.

 

[Tomdawn]

Ok thank you I am going to go down the route of just draining the raditor I require to change the valve on if possible. Am I right in saying the way to do this is to open the drain valve with a hose to outside. Then just open the bleed valve on the one raditor that I need to change the valve on? Thanks for your help.

 

[nickso]

Ok thank you I am going to go down the route of just draining the raditor I require to change the valve on if possible. Am I right in saying the way to do this is to open the drain valve with a hose to outside. Then just open the bleed valve on the one raditor that I need to change the valve on? Thanks for your help.

It might get most of it out but be cautious when cracking the TRV joints, remove it slowly and carefully too. Is the drain point at the bottom of the system? Incredible the amount I see that are not. Use the drain point to take the pressure off the system anyway. Then you can try it your way or do it as I said above.

Just in case you are a bit useless (no offence ) please make sure you have the correct sized valve and that it will fit the old pipe fittings, especially if you are not going to remove the old olive. Seen some fabulous disasters involving male and female fittings

 

[Tomdawn]

nickso,
Could you describe to me how you would undertake this task. By realsing the pressure do you mean by opening the drain valve? Thanks for any more help.

 

[nickso]

Yes, just open the drain valve. I would do it the way I wrote it in my first post.