How to safely isolate Main Combi 24 HE Boiler

[Callum Shipley]

Hello,

I'm a new flat-owner and plumbing novice. I've never had a combi boiler before. I need to change the cartridge in my shower-room tap (a single lever mixer), which has started leaking.

I've done some investigating and so far:
1. It seems that this tap is on another cold water line to what seems to be the main line. This main line is in the kitchen and when I turn that off the cold water to the kitchen and shower is turned off. The shower-room tap still flows.
2. I've searched the flat but there seems to be no other main line to turn off.
3. The isolation valves on the cold and hot inflow pipes to the shower-room tap do not work properly as water still flows. I can get the cold water to stop now (after a lot of opening and closing) by turning off both the main tap in the kitchen and the cold isolation valve. The hot isolation valve still does not stop the flow.

My plan now is to shut off the hot water from the boiler to the tap. My concern is about damaging the boiler: I don't want to create an air bubble, for example. How can I do this safely?

I've attached a picture of my boiler. I've used the filling loop before (the two pipes right of centre connected by the flexible steel hose) and the central uncovered pipe is gas. The plastic pipe on the far right is overflow but I'm not sure what the uncovered pipe next to the plastic pipe is. The pipe second from left is hot outflow (this gets hot when the hot tap is open) but I'm not sure what the far left pipe is.

Can I just turn off the boiler and then shut off the cold inflow into the boiler, first at the mains tap in the kitchen, and then the valve on the cold inflow pipe(s)? As the hot-water outflow pipe from the boiler has no tap then will this cause a problem?

Thanks so much!

 

[Aire]

This isolates the cold feed into the boiler.

 

[Rob Foster]

Hello,

I'm a new flat-owner and plumbing novice. I've never had a combi boiler before. I need to change the cartridge in my shower-room tap (a single lever mixer), which has started leaking.

I've done some investigating and so far:
1. It seems that this tap is on another cold water line to what seems to be the main line. This main line is in the kitchen and when I turn that off the cold water to the kitchen and shower is turned off. The shower-room tap still flows.
2. I've searched the flat but there seems to be no other main line to turn off.
3. The isolation valves on the cold and hot inflow pipes to the shower-room tap do not work properly as water still flows. I can get the cold water to stop now (after a lot of opening and closing) by turning off both the main tap in the kitchen and the cold isolation valve. The hot isolation valve still does not stop the flow.

My plan now is to shut off the hot water from the boiler to the tap. My concern is about damaging the boiler: I don't want to create an air bubble, for example. How can I do this safely?

I've attached a picture of my boiler. I've used the filling loop before (the two pipes right of centre connected by the flexible steel hose) and the central uncovered pipe is gas. The plastic pipe on the far right is overflow but I'm not sure what the uncovered pipe next to the plastic pipe is. The pipe second from left is hot outflow (this gets hot when the hot tap is open) but I'm not sure what the far left pipe is.

Can I just turn off the boiler and then shut off the cold inflow into the boiler, first at the mains tap in the kitchen, and then the valve on the cold inflow pipe(s)? As the hot-water outflow pipe from the boiler has no tap then will this cause a problem?

Thanks so much!

View attachment 36176

When you do this DO put the plug in the bath waste or cover the shower waste, bits and bobs can fall out during your work and its worse when they roll along and into the plughole and trap, I know did this once eons ago. Rob Foster centralheatking

 

[snowhead]

You could stand over a sink or bath all day with a box of screws trying to drop one straight into the waste.
You'll never do it.

Take the screw out of a tap top and put it "Safe" and you'll knock it down the waste first time without any effort.

Same goes for radiator bleed screws and gaps under skirting.

 

[Pickwickpick]

You could stand over a sink or bath all day with a box of screws trying to drop one straight into the waste.
You'll never do it.

Take the screw out of a tap top and put it "Safe" and you'll knock it down the waste first time without any effort.

Same goes for radiator bleed screws and gaps under skirting.

So true and the worse is you usually see it all happening in perfect slow motion! Horrible heart sinking feeling!

 

[Callum Shipley]

Thank you all for your advice. The waste shall be covered!

I have one lingering concern though. As the hot isolation valve on the tap doesn't close fully, might that let air into the boiler through the hot outflow pipe? Or, am I being overly worried?

 

[Aire]

Thank you all for your advice. The waste shall be covered!

I have one lingering concern though. As the hot isolation valve on the tap doesn't close fully, might that let air into the boiler through the hot outflow pipe? Or, am I being overly worried?

Your been overly worried, air can cripple a heating system but doesn't generally cause issues with mains supplies. When you turn the water back on the supply may have air in it which will cause your tap to spit and gurgle at you so just open the taps slowly until the air has gone and you have a steady flow.

 

[Callum Shipley]

Brilliant, thank you.