15mm or 22mm pipe to H?C shower valve

[Deansplit]

I had this dilemma with rads!... now with a shower, lol!

I have 2-3 bar pressure. I'm fitting a shower which I haven't actually bought yet, but want one with jets. My system is a Santon 210L unvented cylinder & the shower is 9m from it. I'm told that 22 will give more volume but this always confused me as surely it's determined by how much can exit the end shower head anyway, usually 15 aren't they? I notice some valves are 15 & some 22mm male BSP connections though.

I will also be supplying to 2 sinks (one for the same en suite, one for one a floor below) which flagged up another issue - if use 22 it will take much longer to get hot at the tap for the times when u wash hands after the loo, plus leave more HW going to waste. I guess I could use a separate 15mm feed for the sinks to avoid this, (weighing up basin HW vs shower usage - sinks will be used more often) but is that a bit of an odd thing to do?

To top it all, I notice my main CW stop cock is a 15mm connection anyway! Surely, using anything larger than 15 will never maximise its capacity anyway? Or does it not work like that? We are doing a kitchen extension anyway so I will be able to find the main in and see if it can be changed to 22, guess that'd be a good idea to do regardless?

Any help appreciated

Cheers

 

[bengasman]

No point using 22 if part of the supply is 15, and it would take twice as long to get the hot if you used 22

 

[Deansplit]

yea that's what I thought. But 'if' I can change the stop cock to 22, and the valve a want has 22 BSP connections, is it best to use a 22mm feed?

 

[bengasman]

Not really. It is rather unlikely that you will find a 15 mm stopcock on a 22 mm pipe. If you upgrade a water supply, you have to make sure that there is no 15 mm, or 1/2" ANYWHERE upstream if you want to achieve a noticeable difference.

 

[Deansplit]

I have the 80% of the house apart! The 15mm stopcock goes to a 28mm main cold feed to the top of the house for wc's elec showers and cold taps etc, plus to feed the HW cylinder. the only part I don't have apart at the mo is the kitchen. Once the founds are dug I'll be able to see the main in from the road. so I wasn't saying it's a 15mm stopcock on a 22mm pipe, was suggesting removing everything back to the 25mm blue pipe and change to 22 or even 28?

Point taken about if there's any 15 upstream it defeats the object of using 22, so not sure why 'any' of the house is in anything other than 15 anyway then, or is this standard practice? It's a Victorian house.

 

[TicklyT]

Point taken about if there's any 15 upstream it defeats the object of using 22, so not sure why 'any' of the house is in anything other than 15 anyway then, or is this standard practice? It's a Victorian house.

The original victorian plumbing may just have been a 1/2" (they hadn't invented millimetres then, or if they had, they didn't trust them on account of being French) rising main, probably lead, with one tap on the end located in the scullery. That's it.

As things moved on, a hot water system, fed by extending the 1/2" main to the loft to fill an open storage tank, became standard practise. The tank was necessary because you couldn't instantly 'turn off' a solid fuel range cooker, usually incorporating the boiler, if the water supply failed. Hot water outlets were fed via the tank with 3/4" pipe, or larger, because the storage tank provided little water pressure, needing larger pipes and taps to get a decent flow rate.

Moving on a century, better heating controls and boilers became available, so mains pressure systems were practical. They may have worked just as well as older systems by just using 15mm pipe, but few would have replaced perfectly functional 3/4" or 22mm pipes with 15mm just to save a bit of fuel and water.

Modern expectations are greater, so now the original 1/2" supply pipe is often found wanting. If you have the whole house in pieces, now is a good time to consider re-piping everything in line with modern practises and expectations.

 

[mysteryman]

You seemed to suggest that the main is blue 25mm. If so, put a 25 - 22 stop tap in and run to the start of your 28 in 22mm. Or get a 25 - 25 stop tap and increase to 28 from there.

 

[Deansplit]

so now the original 1/2" supply pipe is often found wanting

So are you saying 1/2" is OK or should be replaced for 22?

 

[bengasman]

1/2" is virtually the same as 15 mm

 

[Deansplit]

Sorry, when I say 1/2" I mean 15 anyway - so do u mean 15 is Ok or switch to 22?

 

[Deansplit]

Right, ground all up now and can see that the 'lead' pipe in is 3/4, then has what looks like a welded joint to 1/2" for 8" or so, then the stop cock and then 1/2" into the house to the internal stopcock. I guess the best option is to join a 22mm stop cock to the 3/4 lead pipe, and then 22 to an internal one and 22 onwards to whole house? But how do I turn water off from the road? Is this a water services job or can I do it?

 

[bengasman]

Water company won't come out to turn your water off, you have to find your street valve.
Best thing if half possible, replace the horrible led with 35 mm ground pipe.

 

[Deansplit]

Hi

Just coming back to this as been away - to recap, situation is thus:

- Want to have a powerful shower with a few body jets.

- Main in is currently a 3/4" lead pipe, with a welded reduced 1/2" pipe to a stop cock, then copper 15mm from there, albeit eventually to a 28mm to feed the entire house. The pressurised cylinder has a 22mm hot feed out of it.

- At the top of this 28mm, I want to feed the shower valve which may have 22mm connections (haven't bought it yet)

- I 'will' be applying to NI Water to replace the lead pipe to the property and whilst the house is apart, it's not much effort for me to run any size of pipe to connect to their new one. So I presume I'll connect to it with 22, 25 or 28mm?


So, my question still stands: what size pipe do I branch off the hot and cold supplies? I was thinking 22 would give me greater power? If so and the valve I choose has 15mm connections, do I reduce just before them? I am aware hot water will take longer to reach (it's about 9m from cylinder) but if it's a noticeable difference in power than using 15, I'd do it, I can always run a separate 15 to the basin for less wasted HW each time the sink tap is used.

Helpful comments so far, many thanks for any further help in making my decision.

 

[JohnD]

the lead pipe that you say is 3/4", is very likely 1/2" or less inside (lead pipe is very thick)

it sounds like this would be a good time to replace it all, right up to the boundary, with 25mm or 35mm plastic, and a big new stopcock. You will be amazed at the improvement in flow and apparent pressure.

I recently replaced an old victorian lead pipe, it was 3/8" bore inside, and parts of it had been bent or squashed. It had a wiped lead joint to a 1/2" ish bronze stub for the stopcock.

View media item 23857
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it was very difficult to join up to the old stub, as the water company would have charged me £500 to dig up the pavement (which would have made a better job, but I was too mean)

 

[Deansplit]

Thx for pics John. I have already contacted the water Co - they say 'if' we qualify for a LPR then the civil works on the pavement is free. So really hoping we get accepted (whatever the credentials are!!?).