How to release water in combi boiler to repair a leakage？

[LLL]

Hello, one of my radiators is leaking, quite seriously,  can be 600ml everyday, i want to repair myself, but the issue is I don't know how to remove the water from the whole boiler system since the leaking point of the radiator is collecting with the main pipe, my boiler is Worcester Bosch Greenstar 8000 Life 30kW Combi Boiler. Someone said can release water from one of the radiators, but i was thinking release it from the boiler directly might be quicker and easiler? Can anyone suggest how to do so? Also someone suggested to use sealant on the leaking point, does it work? 

[Ajm]

you need to look for a drain cock low down on the system somewhere

 

looks like

 

 

attach a hose to the outlet and open the valve on the left for it to drain

[Big Jimbo]

I'm rubbish with computers, but i have just looked up the manual on line. The drain off is clearly shown in the manual. Google is your friend

[LLL]

14 hours ago, Big Jimbo said:

I'm rubbish with computers, but i have just looked up the manual on line. The drain off is clearly shown in the manual. Google is your friend

Thank you so much! I’m a new DIYer, trying to learn from the internet, from everyone here, and from GPT. I’ve found the drain point (25) as you suggested, but it looks like I need to open the front cover of the boiler — which is a bit scary for a beginner like me. Are there any unforeseen problems if I simply follow these steps: turn off the power, open the front cover, drain the boiler through the drain point, fix the leak, and then top up the water?

 

[LLL]

15 hours ago, Ajm said:

you need to look for a drain cock low down on the system somewhere

 

looks like

 

 

attach a hose to the outlet and open the valve on the left for it to drain

I did not find this one around the boiler, is it typically connected with a radiator? I think I saw one in my office. 

[Ajm]

Drain cock could be anywhere on the system - and there might be more than one!

 

They should be at low points so the water can drain away from as much of the system as possible. Also helps to open air bleed screws on radiators to let air in as the water escapes.

 

Draining from the boiler won't drain from the radiator if the radiator is lower down. I'm only a DIY but have done quite a bit of work on central heating and have never drained system by dismantling boiler! Always find the drain cocks.

[SimonD]

10 hours ago, LLL said:

Thank you so much! I’m a new DIYer, trying to learn from the internet, from everyone here, and from GPT. I’ve found the drain point (25) as you suggested, but it looks like I need to open the front cover of the boiler — which is a bit scary for a beginner like me. Are there any unforeseen problems if I simply follow these steps: turn off the power, open the front cover, drain the boiler through the drain point, fix the leak, and then top up the water?

 

 

Don't start taking your boiler apart for this. Technically you need to be Gas Safe registered as the casing forms part of the flue system by creating the room seal which is an essential safety part of the boiler. With the casing off the boiler is no longer room sealed.

 

Draining the boiler from this point is only for when you are completing repairs on the boiler.

 

Also, this boiler has lots of plastic fixings and these can break, which could make putting the case back on and fixing it properly difficult.

 

Look for your drain cock on the radiator pipework instead!

[marshian]

For me the first thing to establish is what is actually leaking

 

is it

 

A. the lockshield valve gland

B. the compression fitting to the 15mm feed/return pipe

C. The compression fitting to the rad tail 

D. The rad tail 

 

Once identified you can consider if whole system needs to be drained or if a partial draindown can be carried out

 

For instance if the rad is upstairs then you only need to drain down upstairs to a level where a repair/replacement can be achieved without issue

 

If downstairs then you can shut all of the TRV's and Lock shields upstairs to leave more of the water in the system (downside is it's faff and you need to carefully note down the lockshield positions so you can reset the circuit balance to as it was)

 

I've "hot swapped" a lockshield valve before* but on a tiled floor not carpeted - not sure I'm brave enough to do that on a unvented system (I'm a vented system so the pressure is limited by the head of water in the loft.

 

 

 

 

 

[LLL]

27 minutes ago, marshian said:

For me the first thing to establish is what is actually leaking

 

is it

 

A. the lockshield valve gland

B. the compression fitting to the 15mm feed/return pipe

C. The compression fitting to the rad tail 

D. The rad tail 

 

Once identified you can consider if whole system needs to be drained or if a partial draindown can be carried out

 

For instance if the rad is upstairs then you only need to drain down upstairs to a level where a repair/replacement can be achieved without issue

 

If downstairs then you can shut all of the TRV's and Lock shields upstairs to leave more of the water in the system (downside is it's faff and you need to carefully note down the lockshield positions so you can reset the circuit balance to as it was)

 

I've "hot swapped" a lockshield valve before* but on a tiled floor not carpeted - not sure I'm brave enough to do that on a unvented system (I'm a vented system so the pressure is limited by the head of water in the loft.

 

 

 

 

 

thanks a lot, it is on the second floor and the leaking part is connecting with the main pipe and i have to drain the water, at least the second floor. do i need to shut all TRV's and Lock shields downstairs? Also i try to find the drain cock as Ajm suggested, but still not not find it (try to avoid the drain the whole boiler as Marshian suggested). If there is no drain cock from a radiator, how can i use the radiator to drain? The bleeding? 

[marshian]

1 hour ago, LLL said:

thanks a lot, it is on the second floor and the leaking part is connecting with the main pipe and i have to drain the water, at least the second floor. do i need to shut all TRV's and Lock shields downstairs? Also i try to find the drain cock as Ajm suggested, but still not not find it (try to avoid the drain the whole boiler as Marshian suggested). If there is no drain cock from a radiator, how can i use the radiator to drain? The bleeding? 

How old is the house? 
 

mine was built in early 1980’s they didn’t put any drain valves in at all

 

you can get round this by shutting one rad (both ends - noting the position of the lock shield valve, turns to close or or turns to fully open) once you’ve released the pressure in the system

 

pick a rad pref near a door and on a hard surface like tiles or lino 

 

release the system pressure first using the bleed screw and a jug to collect the water

 

once that’s done shut both valves - crack the union to the rad tail - then drain the rad with suitable tray or tupperware container from the cracked union (plenty of old towels to catch what misses the container

 

when rad is empty you can normally remove the rad fit a new tail to one of the valves with a hose attached and then drain the system via the hose

 

please ask if you want more explanation or pictures and I’ll try to pull a few bits out of my spares pile to illustrate what I’m describing

[Nickfromwales]

Just use the drain off on the magnetic filter, the silver can under the boiler. 
 

Easy! 

 

 

Unscrew the silver cap at the bottom. 
 

The cap then becomes the key to open the valve (see the slotted head in the centre of the cap). Open slowly and drain into a bucket until the system pressure is zero. 

[marshian]

1 hour ago, Nickfromwales said:

Just use the drain off on the magnetic filter, the silver can under the boiler. 
 

Easy! 

 

 

Unscrew the silver cap at the bottom. 
 

The cap then becomes the key to open the valve (see the slotted head in the centre of the cap). Open slowly and drain into a bucket until the system pressure is zero. 

Excellent spot - provided the boiler is on ground floor could you shut all the unaffected rads and drain down the problem one by opening the rad bleed as they will still need to drain to below the level of the lockshield?

 

[Nickfromwales]

1 hour ago, marshian said:

Excellent spot - provided the boiler is on ground floor could you shut all the unaffected rads and drain down the problem one by opening the rad bleed as they will still need to drain to below the level of the lockshield?

 

Everything at / above the point you want to open the system needs draining down.

[Nickfromwales]

Where is this valve leaking from exactly? 
 

[marshian]

15 minutes ago, Nickfromwales said:

Where is this valve leaking from exactly? 
 

I already asked that 🙂

[Nickfromwales]

36 minutes ago, marshian said:

I already asked that 🙂

oops.

 

Did you get an answer..... 

[LLL]

Sorry, i missed that one, it is point A leaking unfortunately. 

[LLL]

4 hours ago, Nickfromwales said:

Just use the drain off on the magnetic filter, the silver can under the boiler. 
 

Easy! 

 

 

 

Unscrew the silver cap at the bottom. 
 

The cap then becomes the key to open the valve (see the slotted head in the centre of the cap). Open slowly and drain into a bucket until the system pressure is zero. 

thank you so much! I am really beginner!  But can you please tell which point I should open? I assume it is B? 

 

 

 

[Nickfromwales]

2 minutes ago, LLL said:

Sorry, i missed that one, it is point A leaking unfortunately. 

Ok. I asked because C shows signs of oxidisation of the brass (it's turned green) so that has leaked at some time too.

 

Simple answer here is to just replace the valve with a new one. You can go for one with a DOC (drain off cock) LINK and this will be a straight swap.

 

My guess here is that the chrome nut A wasn't made up with any pipe jointing compound LINK...or the olive behind that nut is squashed from overtightening. Have you used a spanner to try to tighten this up at all?

 

 

[Nickfromwales]

Just now, LLL said:

thank you so much! I am really beginner!  But can you please tell which point I should open? I assume it is B? 

 

 

 

Yes, B will screw off with zero water coming out, as long as the valve D is at 90 degrees (flat) and not turned open in line with the silver can. Loosen it one turn at a time, and after 3 or 4 turns it will come away. The thread you have left will go to a Hozelock hosepipe fitting for a garden hose, if you want to drain to outside LINK (take the white 1/2" bit out and use the yellow 3/4" one   

[Nickfromwales]

 

When the cap is off, A is the key you use to turn valve B. 

 

That is a 1/4 turn valve, so a lot will happen with only a small amount of opening!!
 

Be ready with the bucket (get your wife to hold it and say nothing until “surprise!” lol. 🥳.). 

[LLL]

10 minutes ago, Nickfromwales said:

Ok. I asked because C shows signs of oxidisation of the brass (it's turned green) so that has leaked at some time too.

 

Simple answer here is to just replace the valve with a new one. You can go for one with a DOC (drain off cock) LINK and this will be a straight swap.

 

My guess here is that the chrome nut A wasn't made up with any pipe jointing compound LINK...or the olive behind that nut is squashed from overtightening. Have you used a spanner to try to tighten this up at all?

 

 

Yes, you are right, it was a bit leaking and then i tried to use spanner to tighten, at the beginning, it stopped but suddenly leaking is getting worse, 400ml everyday at least. thanks for the link i wil buy one to replace all, but I worry about the pipe is broken, if that is the case, shall I cut a bit of the broken part but this side will be shorter, how to do so? 

[LLL]

19 minutes ago, Nickfromwales said:

Ok. I asked because C shows signs of oxidisation of the brass (it's turned green) so that has leaked at some time too.

 

Simple answer here is to just replace the valve with a new one. You can go for one with a DOC (drain off cock) LINK and this will be a straight swap.

 

My guess here is that the chrome nut A wasn't made up with any pipe jointing compound LINK...or the olive behind that nut is squashed from overtightening. Have you used a spanner to try to tighten this up at all?

 

 

regarding the part to be replaced, i prefer to have a standard one without drain off integrated, is this the right size? it says 15mm x 21mm ? https://www.screwfix.com/p/flomasta-15mm-x-21mm-white-chrome-angled-modern-manual-radiator-valve-head-body/901FW?tc=JS6&gclsrc=aw.ds&gad_source=1&gad_campaignid=22599672207&gbraid=0AAAAAD8IdPxM6oUdBmgO3Bj95chXkP4CE&gclid=Cj0KCQjwl5jHBhDHARIsAB0YqjzybO3b1TquRdHVwV4-L2UsWMD9StnnHwgBZ53aXbVFhr-NDXJtj6UaAi4TEALw_wcB ? 

[Nickfromwales]

Just now, LLL said:

regarding the part to be replaced, i prefer to have a standard one without drain off integrated, is this the right size? it says 15mm x 21mm ? https://www.screwfix.com/p/flomasta-15mm-x-21mm-white-chrome-angled-modern-manual-radiator-valve-head-body/901FW?tc=JS6&gclsrc=aw.ds&gad_source=1&gad_campaignid=22599672207&gbraid=0AAAAAD8IdPxM6oUdBmgO3Bj95chXkP4CE&gclid=Cj0KCQjwl5jHBhDHARIsAB0YqjzybO3b1TquRdHVwV4-L2UsWMD9StnnHwgBZ53aXbVFhr-NDXJtj6UaAi4TEALw_wcB ? 

Yes 

[Nickfromwales]

When the pressure is zero on the boiler gauge, the system and radiators will still be nearly 100% full, if they are not on the next floor up above the boiler.

 

You need to drain down the radiator you’re working on. Get one of these LINK and a radiator key LINK to open the vent at the top of the radiator. Until you open that, the water will stay in the radiator on vacuum. 
 

Drain out until there’s no more water to come out.

 

Then fit the new valve. You need to get some PTFE tape LINK to go around the olive on the pipe (where you fear you’ve ’broken’ the pipe). You know when you’ve done this as the leak goes from bad to very bad.

 

Applying this tape (10 turns) is to cover you from the olive having been crushed a little too much by over tightening with a spanner.

 

Smear some jointing compound over the threads, over the olive (after tape) and this will mean you get a good seal without having to go Hulk on the spanner again. For the next tightening up, go easy, and try it first. Then go tighter just a 1/4 turn at a time if a small leak begins to show.
 

 

The you close the vent at the top of the radiator.
 

Then you go to the boiler and test fill the system back up to 1.5 bar on the gauge to check for leaks. If all good after 30 minutes, then bleed the radiator vent to get the air out.

 

Then top the pressure back up (letting air out will make the pressure drop again on the boiler gauge) and run the radiators up to max temp for 30 mins and keep checking.

 

If all good, select a nice shirt and get to the pub to celebrate. 🍾