Valveless manifold

[Mr Blobby]

I had assumed my plumbing manifolds would be fitted with individual isolation valves.  

 

 

Assuming my plumber has no intention of fitting valves to these manifolds, then please tell me that (a) it doesn't matter, or (b) an alternative product with valves.

 

Three of our HW (showers and bath) pipes are wider diameter than the rest.

 

Edited June 27 by Mr Blobby

[JohnMo]

The biggest advantage of a manifold is the isolation valves in my opinion. They allow parts of the system to taken offline while the rest stays active.  No a no valve manifold is a missed opportunity. Just look at Screwfix they offer a couple of different options.

[-rick-]

What did you specify/agree to for this installation? Has he put isolators at the other end?

 

That would be what I’d imagine an uncreative plumber not used to installing manifolds would do. (afaik isolators somewhere are a requirement, exact location isn’t)

 

I don’t see the logic in doing it that way. You want a way to isolate leaks. Best place to do that is at the branch point of the circuit (*). Gonna be a pain in future if you want to change things as is. So I would put my foot down in your position and have them fitted at the manifold.

 

* whether you want a second isolator at the end of the pipe is a question. If they are already there I don’t think I’d bother removing them. My experience with isolators is that they have leaked more than I’ve needed to use them as isolators, so I think I’d be inclined not to duplicate. Though from reading here it sounds like the leak issues are common with cheapo/screwfix type isolators. Higher quality ones are good.

Edited June 27 by -rick-

[Mr Blobby]

Ok, so I could have been more specific, but really, specifying a manifold without valves is like specifying a car without wheels.  I didn't think I needed to be that specific 😒

 

The problem is my trades always want to do everything at least cost because that's what they always do.  It's just frustrating.  Assume nothing 😬

 

Can valves be inserted here at the junction, or is it entirely new manifolds?

[-rick-]

4 minutes ago, Mr Blobby said:

Assume nothing 😬

 

indeed. I try not to assume but when I do it often comes back to bite me.

 

4 minutes ago, Mr Blobby said:

Can valves be inserted here at the junction, or is it entirely new manifolds?

im not the best person to ask but i believe yes. But if you’ve got a plumber who will always install cheapest available option then you may want to put some effort into specifying better quality valves (or expect leaks at some point).

[JohnMo]

For the cost of manifolds, swop the manifolds for proper ones. These are the first ones I found many other options out there, they just screw together to make as many outlets as you need. Others in the site 

 

https://www.bes.co.uk/riifo-plumbing-manifold-3-4-x-1-2-valved-outlets-4-port-red-levers-27474/

[Mr Blobby]

Does the diameter of the manifold matter?

 

Maincor do a manifold that connects straight to the mlcp pipes but only the 1 inch manifold has connectors for 20mm mlcp.

[G and J]

OK, I’m going to risk sounding dumb now, but is it really worth the effort to replace the manifolds?   Maybe ensure a few isolators are put in so that just the cold or just the hot can be shut off, but given that the horse has bolted will enough time be saved in the future to repay the extra time and delay (and the knock on effects of a pissed off tradesman)?

 

If there’s a leak you shut down, deal with it pronto or whack a stop end on the offending bit till you get the parts.  
 

I maybe guilty of Hep2O think here, but I put isolators everywhere in our last house and in 34 years most of them never got closed off. 

[Conor]

I just put a 22mm isolating valve on each of the manifolds. Not the end of the world.

[Nickfromwales]

2 hours ago, Conor said:

I just put a 22mm isolating valve on each of the manifolds. Not the end of the world.

I'm with you if it saves the cost of "fixing this", but a PITA if @Mr Blobby needs to isolate 1 room.

 

@Mr Blobby Assuming these don't have isolators means your plumbers have installed isolators at each termination point; where this is possible eg kitchen / utility / basins / behind bath panels for bath & showers?

[Mr Blobby]

11 hours ago, Nickfromwales said:

Assuming these don't have isolators means your plumbers have installed isolators at each termination point; where this is possible eg kitchen / utility / basins / behind bath panels for bath & showers?

 

No, no isolators on the other ends that are plumbed so far.

 

Call me cynical, but the way it seems to work is tradesman finds a day he needs to fill.  His regular merchant doesn't have the bits in stock, so substitute with whatever is on the shelves. 

 

I texted the plumber yesterday and haven't heard back so he probably isn't very happy.  But he's going to charge me twice for doing it twice so I don't see the problem.  Besides, this isn't a popularity contest, it just needs to be done right.  The trades already think I'm a pita so I've nothing to lose 😆

 

 

[Nickfromwales]

I guess the M&E spec should have been tighter? Did you tell him to fit manifolds with isolators?

[Mr Blobby]

On 30/06/2026 at 13:54, Nickfromwales said:

I guess the M&E spec should have been tighter? Did you tell him to fit manifolds with isolators?

 

 

... the manifolds were first fitted on the wrong (as per the MandE drawings) wall and I got them moved. But they are still in the wrong place so the cold to the kitchen is now going to be doing its own thing 🤦‍♀️

 

There's no way the plumber is ever going to read the M and E specs 🤷‍♂️ 

 

(Although in fairness a bunch of stuff changed since the original M and E spec hence I'm to blame for not being too strict after the documents were issued)

 

 

Edited Wednesday at 14:19 by Mr Blobby

[Mr Blobby]

🤦‍♀️  

Edited Wednesday at 14:26 by Mr Blobby

[Nickfromwales]

4 hours ago, Mr Blobby said:

the cold to the kitchen is now going to be doing its own thing 🤦‍♀️

It can't do its own things, it needs to be off a balanced cold feed to comply with G3.

 

Plumber sounds like a tit tbf, but if you handed him the spec and he did not grace you with his time to read it, then he'd be told to GFH and pay to change the manifolds on his own time and money.

 

If you didn't then you've fallen onto your own sword.  

[Mr Blobby]

13 hours ago, Nickfromwales said:

If you didn't then you've fallen onto your own sword.  

 

I think I did, TBH.  I should have put the specs under people's noses and banged my fist on the table immediately prior to work being done.  Lesson learned😖

 

Here's the cold feed to the kitchen, coming off the end of the manifold instead of the valved outlet.  Apart from triggering my OCD and not looking as pretty, I'm going to assume this works ok.  Besides, the merchant didn't have another manifold in stock (I could have picked one up quite easily of course).  There is a valve in the pipe just under the photo. 

 

 

 

Manifold is now 1 inch, off a 22mm feed 😕.   

 

 

[sharpener]

On 01/07/2026 at 20:08, Nickfromwales said:

It can't do its own things, it needs to be off a balanced cold feed to comply with G3.

 

Just happened across this thread.

 

Traditionally the kitchen cold supply was the only thing that came directly off the rising main to the tank in the loft, other outlets in the house would come from the (unwholesome) tank.

 

When did this all change to requiring a balanced supply per G3?

 

I suppose this is to ensure the same pressures at a kitchen mixer. If you don't have a mixer (like my separate pillar taps!) does it matter?

[JohnMo]

19 minutes ago, sharpener said:

When did this all change to requiring a balanced supply per G3?

To be frank I've done the course and G3 doesn't mention it directly - But with mixer taps you need a balance pressure between hot and cold otherwise the higher pressure wins and you don't get any mixing.  G3 limits the pressure to the cylinder to 3 bar(g) via a mandatory PRV.  This usually comes in the form of a combination valve which includes a cold take off port for cold water which is also regulated down to 3 bar(g).

 

However if the incoming main has a PRV installed and set to 3 bar(g) or below, the whole house including cold water and hot water cylinder will be at around the same pressure. However if you go this route there is there is a chance of reverse flow so you should install a check valve on the hot water outlet of the cylinder.

 

If you don't have balanced mixer taps, mixer showers, and mixer bath fillers, then no balance feed needed. BUT you do have to include scold prevention measures as no auto regulation of supply temp occurs.

 

29 minutes ago, sharpener said:

other outlets in the house would come from the (unwholesome) tank.

The water in an unvented cylinder is classified as wholesome.

[Nickfromwales]

2 hours ago, sharpener said:

When did this all change to requiring a balanced supply per G3?

It's all about the prevention of backflow from the untamed cold mains > UVC via the hot pipework. If you'd have seen all the installs I have that went horribly wrong, done by clueless / careless / ignorant installers over the years, folk would have a much greater respect for these things.

 

Adding a non return to the hot outlet of an UVC (single check, not a double!) and / or a secondary pressure reducing valve at the stopcock are all retro fit disciplines vs a complete new install, done from scratch; the latter meaning all mixer outlets are fed from balanced feeds. The G3 installation particulars shown in the Benchmark / MI's allows protection for things like mixer taps being changed downstream for 'non-compliant' hardware, which then introduce an issue later on, and more, so you may start with a 2 tap hole sink with separate taps = zero mixing, and then go and buy a monoblock mixer without non return valves supplied in the box, so you don't then fit one on the hot feed to prevent backflow, and then you have caused a serious issue (that you thought was a harmless upgrade).

 

1 hour ago, JohnMo said:

BUT you do have to include scold prevention measures as no auto regulation of supply temp occurs.

Nobody gives 2 shits about this, not even British Gas. Don't hold your breath looking for anyone to care about you getting roasted, as there are too many plumbers out there (on their mothers side).

[G and J]

8 hours ago, JohnMo said:

The water in an unvented cylinder is classified as wholesome.

Crumbs, the things one doesn’t know!

 

Having installed a vented system in our first build in 1991, and having boned up on the rules and best practices then, I’ve got it deep programmed in me that hot water is never potable.  Ever. Never ever. 
 

So here I sit with a UVC, and I think I’m reading that I can fill a pan with hot water from the kitchen tap to boil me broccoli in.  
 

Have I understood correctly?

[Nickfromwales]

50 minutes ago, G and J said:

Crumbs, the things one doesn’t know!

 

Having installed a vented system in our first build in 1991, and having boned up on the rules and best practices then, I’ve got it deep programmed in me that hot water is never potable.  Ever. Never ever. 
 

So here I sit with a UVC, and I think I’m reading that I can fill a pan with hot water from the kitchen tap to boil me broccoli in.  
 

Have I understood correctly?

Yes. Its potable water, typically coming from a stainless steel (ergo food grade) vessel.

 

I often fill the kettle with hot water from my combi boiler, if I know it’s getting filled right up. Doubt it saves money but defo boils in less than half the time which is handy. 

[G and J]

29 minutes ago, Nickfromwales said:

Yes. Its potable water, typically coming from a stainless steel (ergo food grade) vessel.

 

I often fill the kettle with hot water from my combi boiler, if I know it’s getting filled right up. Doubt it saves money but defo boils in less than half the time which is handy. 

Thank you.  
 

We’ve gone for a boiling water tap thingy, partly to keep the small kitchen worktop as clear as possible.  But I’ll do that for me veg.   I’m well up to date, me (for the mid ‘90s that is!)