simple/stupid plumbing question.

skycatcher

Earlier this year I switched from an oil fired pressurised central heating system with hot water cylinder and cold water storage tank to a combi gas boiler.
I have an isolation valve (type you turn on/off with a screw driver) under my kitchen sink after the mains stopcock leading to the rest of the house after a feed to the kitchen taps. When the shower runs or the toilet flushed it generates a lot of noise. Upon investigation I noticed that it was partially closed. So i opened it fully only to find it leaked with some force from the screw so I adjusted and the only place it didn't leak was in its original position.
My question is if I was to replace this valve do I only need to close the stopcock and run the water off in the cold taps and there will be no impact upon my new boiler or the chance of airlocks upon turn it back on. Also do you think will cure the noise problem?

Thanks for reading.

travis-powers

Someone with more plumbing skills will be along shortly, sounds like a cheap isolation valve I would change that for a full bore, but the question is why is it there?
Does your stopcock work?

skycatcher

travis-powers said:

Someone with more plumbing skills will be along shortly, sounds like a cheap isolation valve I would change that for a full bore, but the question is why is it there?
Does your stopcock work?

Yes I wondered that also but I'm pretty sure the stopkcock works as I saw the gas installers turning it off and on when they were doing their work.

Alanp

The isolator you describe sounds like it is an isolator to one of your taps to enable easy changing of either tap, if you turn off the water at the main stopcock then open the tap which the isolator supplies, and , if no water comes out ( other than a little bit, what’s in the pipe) , then you should be able to change the isolator, assuming of course that there’s no cylinder feeding the hot supply ( if the isolator goes to the hot tap)
then you might have to drain down, if it’s just a combo feeding all your water then you should be ok, changing the isolator shouldn’t affect your boiler, but check the gauge is showing the correct pressure when your done, not sure if it will solve the noise problem though, 

skycatcher

Alanp said:

The isolator you describe sounds like it is an isolator to one of your taps to enable easy changing of either tap, if you turn off the water at the main stopcock then open the tap which the isolator supplies, and , if no water comes out ( other than a little bit, what’s in the pipe) , then you should be able to change the isolator, assuming of course that there’s no cylinder feeding the hot supply

No the isolator seems to isolate everthing after the 2 kitchen taps as they have their own valves. I guess I just dont understand how the hot circuit works now its also off the mains with the combi boiler and I'm wary of screwing up the central heating now its working well and devoid of all air (which my previous heating never achieved!).

Bendy_House

Hi Skycatcher.

Sounds as tho' it isolates the rest of the cold water taps & toilets in the house, which I guess is no bad thing as it'll allow you to continue using the boiler for hot water when you work on things like replacing cold tap seals and toilet inlet valves.

Most likely the reason it was set in that position was to prevent the leak! These are prone to this sort of thing - cheaper ones at least. Possibly it was set part-closed in an attempt to control a too-forceful cold flow/too-high a water pressure?

Is this easy to replace, and will it stop the noise? I'd hazard a 'yes' to both. The simplest solution would be to find an isolator of the same dimensions - ie length - and then just swap the valve body, re-using the existing nuts and olives. This should work, but a smear of Fernox Hawk White or similar on the olive and male threads would be a good move. Don't over-tighten the nuts - just do them up firmly, and leave room for a further tweak if needed.

Best, of course, is to replace the whole caboodle, including the nuts/olives. The old ones can be removed in one of two simple ways - if it hasn't been crushed down on the copper pipe too much, then I've found that the careful use of two wrenches ('waterpump' type), set either side of the pipe, with one jaw on the pipe end and the other behind the nut, gently squeezing them both simultaneously, will in most cases shift the nut and olive right down to the pipe end. Then just gently tap the nut from behind using one wrench repeatedly slid down the pipe to knock it fully off.

Or, use a junior hacksaw (or multitool) to cut a neat slot in the side of the olives, stopping short of damaging the pipe! Insert a flat-blade screwdriver and twist.

In any event, choose a FULL-BORE isolating valve. Better, use one with a thumb-turn control. Better still, use a 'lever' type. Since there's a useful valve fitted, I'd make it as easy to activate in the future as possible. (The 'lever'-type valve will most likely be physically longer, so you'd need to be able to trim off a small piece of pipe - can you do this? It's usually very easy with the right tool. Or, just stick to thumb-turn, which is fine.)

But - FULL-BORE!

Close off stopcock, place basin (and towels) under the pipe/valve, close off valve, undo bottom end of valve first and then use the valve itself to control how fast the cold pipe above is emptied. You might want to open an upstairs cold tap in order to allow the pipe to drain as fully as possible, because if you don't do this you can expect the pipe to keep on trickling as air goes in to replace water trickling out - quite annoying.

Once the job is done, open stopcock, check bottom valve connection is ok. Slowly open valve, check no leaks. Go to cold taps (highest upstairs one first, I guess) and open them up slowly too - allow to flow, and expect lots of coughs and splutters.

Jobbie jobbed.

To answer one of your Qs - doing this will not affect the boiler system pressure, or cause airlocks.

skycatcher

Thank you so much  bendy house! I was hoping to just do a like for like replacement and reuse the nuts/olives. How will i know the difference between a full bore and not a full bore? Also, if the hot water system is now driven from the mains why would it not need to be drained also ( this is where my lack of comprehension of this new system comes in).

Section62

skycatcher said:

My question is if I was to replace this valve do I only need to close the stopcock and run the water off in the cold taps and there will be no impact upon my new boiler or the chance of airlocks upon turn it back on. Also do you think will cure the noise problem?

Yes, so long as you switch the boiler off you can turn off the mains water supply and open the kitchen tap to drain off as much water as you can.  There will probably still be some water in the pipe when the kitchen tap has stopped running though.  I would also open both a hot and cold tap upstairs to allow any water in those pipes to drain back out (if it can) via the kitchen tap.

From what you describe it sounds like the leaking isolation valve has been put in so the whole of the house except the kitchen tap can be isolated.  I think this is a good idea because it allows you to still get drinking/cooking water at the kitchen sink whilst the rest of the house plumbing is being worked on.

You also need to make sure the boiler 'filling loop' is isolated (='off') (it should already be) so the circulating water doesn't drain back into your cold water supply.

I would use a full-bore lever valve like this one for the replacement as they seem less prone to leak and are easier to operate -
https://www.toolstation.com/lever-ball-valve/p14624

Bendy_House

skycatcher said:

Thank you so much  bendy house! I was hoping to just do a like for like replacement and reuse the nuts/olives. How will i know the difference between a full bore and not a full bore? Also, if the hot water system is now driven from the mains why would it not need to be drained also ( this is where my lack of comprehension of this new system comes in).

I was going by this, but now realise I'd read too much into it: "I have an isolation valve (type you turn on/off with a screw driver) under my kitchen sink after the mains stopcock leading to the rest of the house after a feed to the kitchen taps. When the shower runs or the toilet flushed it generates a lot of noise."

Where does the supply to the combi come off this pipe? Is it before the isolator (like the kitchen sink) or after? I'd assumed it was after, like the kitchen sink, but realise there was no reason for me to assume this... :-(

So, yes, if this isolator also turns off the hot supply (ie - the cold supply to the boiler), then, yes, you'll also have splutterings from the hot taps while it clears air once the job is done.

You will not, tho', suffer from air-locks since your system is mains-driven, so any air in the pipes will quickly be driven out by the water flow.

The worst that should/will happen from this job (other than a dripping new valve connection 'cos you didn't tighten it enough...) is that the hot and cold taps will splutter when the flow is restored as it expels air in the pipes. This is just not a problem; it just needs doing gently so as not to cause excessive shocks to the pipe.

So, once the isolating valve has been replaced, make sure all the taps are off, and then slowly open the valve, part-way, until the water flow stops - which it will in a few seconds (unless a toilet has been flushed - in which case the toilet needs to fill first). Then you open it fully. Check your nuts aren't leaking (missus!). 

Then go upstairs and open a hot - gently, and part-open. It'll splutter and cough, but ultimately flow smoothly. Repeat for the cold. Repeat for every tap in the house - these should now only have minor coughs, but - again - always open them slowly and part-way to begin with to reduce potential bangs and shocks.

How to tell if it's full-bore? Read the description.

If you post a photo of the miscreant isolating valve, we may be able to guide you further.

skycatcher

Bendy_House said:

skycatcher said:

Thank you so much  bendy house! I was hoping to just do a like for like replacement and reuse the nuts/olives. How will i know the difference between a full bore and not a full bore? Also, if the hot water system is now driven from the mains why would it not need to be drained also ( this is where my lack of comprehension of this new system comes in).

I was going by this, but now realise I'd read too much into it: "I have an isolation valve (type you turn on/off with a screw driver) under my kitchen sink after the mains stopcock leading to the rest of the house after a feed to the kitchen taps. When the shower runs or the toilet flushed it generates a lot of noise."

Where does the supply to the combi come off this pipe? Is it before the isolator (like the kitchen sink) or after? I'd assumed it was after, like the kitchen sink, but realise there was no reason for me to assume this... :-(

So, yes, if this isolator also turns off the hot supply (ie - the cold supply to the boiler), then, yes, you'll also have splutterings from the hot taps while it clears air once the job is done.

You will not, tho', suffer from air-locks since your system is mains-driven, so any air in the pipes will quickly be driven out by the water flow.

The worst that should/will happen from this job (other than a dripping new valve connection 'cos you didn't tighten it enough...) is that the hot and cold taps will splutter when the flow is restored as it expels air in the pipes. This is just not a problem; it just needs doing gently so as not to cause excessive shocks to the pipe.

So, once the isolating valve has been replaced, make sure all the taps are off, and then slowly open the valve, part-way, until the water flow stops - which it will in a few seconds (unless a toilet has been flushed - in which case the toilet needs to fill first). Then you open it fully. Check your nuts aren't leaking (missus!). 

Then go upstairs and open a hot - gently, and part-open. It'll splutter and cough, but ultimately flow smoothly. Repeat for the cold. Repeat for every tap in the house - these should now only have minor coughs, but - again - always open them slowly and part-way to begin with to reduce potential bangs and shocks.

How to tell if it's full-bore? Read the description.

If you post a photo of the miscreant isolating valve, we may be able to guide you further.

You are correct. Three boiler is a  way past the valve in question as it's upstairs. I'll try to get a photo!

skycatcher

The kitchen taps are above this