Draining Hot and Cold supply on Combi Boiler

[Job for dad]

Hi there,

I am a new member to this forum and hope to receive some general plumbing advice. Over the years I have carried out various basic plumbing jobs at my house with an indirect fed supply gas boiler system, fitting new bathroom suites, kitchen sinks ,washing machine supply etc.

Now my daughter has a new starter home equipped with a combo boiler and she wants the bath taps changed for a shower mixer tap. My question is to drain the hot and cold supply to the bathroom taps do I simply turn off the mains water stopcock, switch off the electric supply to the combo boiler and turn on the hot taps or is there more to it than that?

 

[AWheating]

welcome to the forum.

yes your correct. wata off, power off, open hot and cold taps downstairs, open all taps upstairs. Tmv valve may not allow hot tap to drain on bath but will only be a small amount of water. make sure you fit double check valves when you change the tap unless they are already fitted.

 

[josh]

Those combo boilers can be a right job..

 

[Ermintrude]

Fit a thermostatic mixer?

 

[AWheating]

tmv is standard on new build baths.

 

[Centralheatking]

What a good post 'job for dad' you seem reallty quite experienced and your
query and plan is spot on. I think you are looking for a 'deck mixer' bathtap unit
Have a look at BES Birmingham - Electric Avenue before you buy -they are
mail order and top boys- dealt with them for years and sensible prices
Centralheatking

Hi there,

I am a new member to this forum and hope to receive some general plumbing advice. Over the years I have carried out various basic plumbing jobs at my house with an indirect fed supply gas boiler system, fitting new bathroom suites, kitchen sinks ,washing machine supply etc.

Now my daughter has a new starter home equipped with a combo boiler and she wants the bath taps changed for a shower mixer tap. My question is to drain the hot and cold supply to the bathroom taps do I simply turn off the mains water stopcock, switch off the electric supply to the combo boiler and turn on the hot taps or is there more to it than that?

 

[Ermintrude]

tmv is standard on new build baths.

No I meant a thermostatic mixer tap. Mira do one so do Bristan as does Victoria plumb.

 

[jaydebruyne]

welcome to the forum.

yes your correct. wata off, power off, open hot and cold taps downstairs, open all taps upstairs. Tmv valve may not allow hot tap to drain on bath but will only be a small amount of water. make sure you fit double check valves when you change the tap unless they are already fitted.

Hi AW,

I just want to confirm something about your post if that's ok? (I've just passed the 6035 so I'm still wet behind the ears).

The reason for opening the taps is to drain the residual water? I would have thought nothing would really come out since turning off the water at the main stop valve. And being that the hot water is instantaneous from the combi so there's no storage. So it's made me think and question myself. The rest of the post I fully understood (thankfully).

I'm very aware I may get pounced on being a fledgling and all. But I'm eager to learn as much as I can so I'll stick my neck on the chopping block and bite the bullet!

Cheers

 

[solutions]

The pipe run alone will store plenty of water to cause a mess. Opening a hot tap down stairs and the hot taps upstairs should drain most of it out, leaving you free to cut in to the pipework or remove taps etc. 1 tap is not normally enough on a combi or unvented as there is no vent so without opening multiple taps ideally on different floors the water in the pipe will be held as there is no open end to draw air in through. Same applies to cold taps if mains fed.

 

[jaydebruyne]

The pipe run alone will store plenty of water to cause a mess. Opening a hot tap down stairs and the hot taps upstairs should drain most of it out, leaving you free to cut in to the pipework or remove taps etc. 1 tap is not normally enough on a combi or unvented as there is no vent so without opening multiple taps ideally on different floors the water in the pipe will be held as there is no open end to draw air in through. Same applies to cold taps if mains fed.

Gotcha! Thanks for the reply, much appreciated

 

[oz-plumber]

Personally,
I wouldn't turn the water off - I would just freeze the piping, olive connectors and flexi's.

Don't have to drain the system, don't have to bleed / flush the system and the customer can still use the water as you are doing the work.

 

[AWheating]

Personally,
I wouldn't turn the water off - I would just freeze the piping, olive connectors and flexi's.

Don't have to drain the system, don't have to bleed / flush the system and the customer can still use the water as you are doing the work.

Its poinltess, it's a 1 min job to turn off the water and drain and a 1 min job to turn back on and remove air. Pointless spending money freezing pipework on a small simple system. I fact freezing would make the job take a lot longer. There should be isolation valves on the bath taps anyway if the house has been plumbed to meet water regs.