DHW manifold arrangement - options?

[Super_Paulie]

hello gentlemen.

Im in the middle of a full house reno. Well a big extension which has basically wrecked every room so may as well be. It seems a good opportunity to re-do all the plumbing and replace the decades of branches, dead legs, all types of fittings etc and go for something straightforward with minimal joins from A to B and manifolds seem to fit the bill. Not a lot online really and almost all searches end up here so i thought id join in. By manifold i mean copper tees with full bore lever valves and double checks.

The situation is "Boiler in loft - Mains downstairs."

I really wanted a central point of isolation for everything, or most things at least so keeping joints to a bare minimum but it has created a few issues. Under the stairs is a bunker that is ideal to house it all but the problem is that the DHW will have to come down from the loft (via the spare room, straight down the outside of the defunct chimney breast) bypassing the bathroom (next room along), straight past the kitchen to the manifold location and then back again to the kitchen and back up again to the bathroom. Common sense suggests this is silly, with a distance around 20/25m in total before hot water gets to the tap which is in reality nearest the boiler. So begs the question do i have a manifold upstairs to split the DWH to the bathroom and kitchen. And if im doing that then i may as well but a manifold in the kitchen as well. And if thats the case then i may as well sack off the manifold in the bunker altogether which was the entire point of it... Before this post gets too long, should i just abandon the whole idea, its been working fine as a branch system for decades...

Attached image, fish is not to scale. Nothing is off the table, the house is in a almost complete reno mode.

[Temp]

Perhaps run cold main up to the boiler and the hot and cold from there to the upstairs bathroom and from there down  to the understairs bunker. 

[Super_Paulie]

43 minutes ago, Temp said:

Perhaps run cold main up to the boiler and the hot and cold from there to the upstairs bathroom and from there down  to the understairs bunker. 

i hear what youre saying, so like this. Would involve "an upstairs manifold" but that wouldnt be a huge burden in the scheme of things.

 

 

[JohnMo]

You really need to keep the pipe runs pretty short or you will not get the hot water to the tap before you want to switch it off.

 

Cold main in valve and tee to downstairs manifold and the to boiler.

 

Hot

Do you need the downstairs manifold, your runs would be much more simple from the upstairs manifold and 

 

 

[Temp]

1 hour ago, Super_Paulie said:

i hear what youre saying, so like this. Would involve "an upstairs manifold" but that wouldnt be a huge burden in the scheme of things.

 

 

 

No I was thinking more like this but perhaps the run to the kitchen tap is too long..

 

 

[Super_Paulie]

8 minutes ago, Temp said:

 

No I was thinking more like this but perhaps the run to the kitchen tap is too long..

 

 

 

ideally yeah, but sadly i cant get from the bathroom to the bunker "easily". The downstairs is all open plan and no matter how i jig it i cant get an easy route from bathroom to bunker, hence the long way round via the kitchen. Sorry that isnt clear from the diagram, its not as straightforward as it seems in terms of house layout. Essentially the bunker is only accessible from the kitchen lets say.

[Super_Paulie]

27 minutes ago, JohnMo said:

You really need to keep the pipe runs pretty short or you will not get the hot water to the tap before you want to switch it off.

 

Cold main in valve and tee to downstairs manifold and the to boiler.

 

Hot

Do you need the downstairs manifold, your runs would be much more simple from the upstairs manifold and 

 

 

i could, but i was under the impression that it is better without any joints outside of the manifolds Open to all suggestions though, so like this?

 

 

 

Edited April 21, 2023 by Super_Paulie

[Temp]

13 minutes ago, Super_Paulie said:

 

ideally yeah, but sadly i cant get from the bathroom to the bunker "easily". The downstairs is all open plan and no matter how i jig it i cant get an easy route from bathroom to bunker, hence the long way round via the kitchen. Sorry that isnt clear from the diagram, its not as straightforward as it seems in terms of house layout. Essentially the bunker is only accessible from the kitchen lets say.

 

Ok then I think I would either put a hot manifold in the kitchen or if no room just run pipes with isolation valves.

I've only shown one hot pipe to the living room /aquarium end but perhaps you need two. 

 

 

[Super_Paulie]

yeah, the 2 hots (and colds) going that way are 1xh&c for the fish tank and the other 2 are outside of the building for car/dog washing. Obviously i can "tee" these nearer the source but i was hoping to avoid any of that stuff.

There seems to be a lot of ways to do business but it always ends up with "tees" here and there or hot manifolds at one place and cold the other which makes me think that the whole manifold and jointless pipe runs is just a bit silly in my situation.  What you have above is close to what i had originally designed with a hot manifold in the kitchen and the cold in the bunker. If i need to add branches in here and there then its not far off that already so i might be chasing a solution to a problem that doesnt really exist. its annoying as the bathroom manifolds are like 2m away from the bunker but you cant get through the staircase to join the 2.

 

Im thinking that the wait time for hot water in the kitchen might not be a huge burden as i barely use it anyways, its the hot in the bathroom that needs the quick response so maybe im over-thinking this... seen too many pictures online of nice manifolds and wanted a piece of the action.

Edited April 21, 2023 by Super_Paulie

[Super_Paulie]

the more i press buttons the more complicated this thing gets...

 

 

[JohnMo]

I kept mine really simple, boiler in loft/plant room. Hot from boiler tees off left to kitchen on its own isolation valve, to the right travels downstairs to utility cupboard, where my cold water manifold is. Everything else goes from there.  Only have one feed to each wet room. Everything in a room is just just goes to a branch system.

 

 

Top blue valve is a 22mm feed to plant room, bottom 15mm isolation valve next to stop cock is the outside tap.

 

On the upper manifold the left pipe is the hot water feed from plant room

[Super_Paulie]

think im just massively over-comlicating things for whatever reason, think a hybrid of branch and manifold might be the better way to go like you have there Johnmo.

[Super_Paulie]

is there any value in using 22mm to my cold water "satellite manifolds"/branch sections to the kitchen and upstairs/boiler rather than just do the lot in 15mm for neatness? Boiler is a 15mm input, mains is 25mm. 

Also i assume having the double checks at the actual outlet is better than having them at the beginning of the run directly underneath these lever valves? Cheers gents., image is in colour for eye candy.

Edited April 24, 2023 by Super_Paulie

[JohnMo]

I did mine in the smaller size instead of 22mm. No flow issues.

 

[Super_Paulie]

anyone available for a sanity check on this setup? 

I ran a test on the time it took water to get down from the loft to the bunker and then back over to the kitchen and it wasnt a problem worth worrying about.
This setup will have a secondary manifold at the kitchen side for cold otherwise the bunker just gets crazy crowded with pipes and it means i can bring each appliance online as and when its positioned, i dont know their final locations just yet so it just makes sense. Drain-offs so i can drain the system down from any of the lines by opening closing the manifold valves. Run to the kitchen tap from manifold is 7m so worth bringing down to 10mm?

 

Without applying favouritism, @Nickfromwales seems the go-to man for manifolds but id love to hear any responses on this from anyone who has experience. 

[Nickfromwales]

For 7m 10mm would suffice, but won't give the welly that 15mm would. The issue with manifold systems is the large bore pipework upstream, so folk / other plumbers may not factor in getting that additional volume of dead leg out and thorough the small bore pipe, also.

 

As for the above drawing, why do you have a manifold tap feeding the 2 downstream manifolds separately? Why not just use a 4-port for the hot and put the DOC ( drain off cock ) on the end of the manifold; with a 3/4" x 1/2" bush and a 1/2" threaded DOC.

The 2 outlets "front" and "rear" will be restricted to the output of "garden" so is not the best layout IMHO.

[Nickfromwales]

On 24/04/2023 at 15:18, Super_Paulie said:

is there any value in using 22mm to my cold water "satellite manifolds"/branch sections to the kitchen and upstairs/boiler rather than just do the lot in 15mm for neatness? Boiler is a 15mm input, mains is 25mm. 

You should have 22mm pipe from the cold stopcock, all the way to the last cold water T-off before the combi, and only reduce to a 15mm cold feed from there > combi. That will give the combi "cold mains priority".

[Super_Paulie]

thanks a lot @Nickfromwales, for your time and advice. Thats exactly why i joined the forum to get help from decent blokes like yourself.

 

Im with you, the 2 additional manifolds in hindsight are pointless, i was just looking for a way to pull the plug on both at the same time which seems ludicrous thinking back as they both have their own isolation anyways...

 

I can run a dedicated 22mm feed to the boiler no problem at all, as i say the whole house is fair game in its current state. This makes more sense?

 

 

[Super_Paulie]

On 29/04/2023 at 09:16, Nickfromwales said:

You should have 22mm pipe from the cold stopcock, all the way to the last cold water T-off before the combi, and only reduce to a 15mm cold feed from there > combi. That will give the combi "cold mains priority".

further to this @Nickfromwales, if i take a 22mm all the way to the combi, what would be the benefits of that as apart from the CH everything else is in 15mm.

Cheers gents.

[Nickfromwales]

2 hours ago, Super_Paulie said:

further to this @Nickfromwales, if i take a 22mm all the way to the combi, what would be the benefits of that as apart from the CH everything else is in 15mm.

Cheers gents.

The flow rate at the combi boiler cold inlet is what pushes hot water out of the taps. As you are "stealing" from the rising cold supply to it, multiple times before it gets to the combi, you will likely see a significant loss in performance for the DHW output. If you run 22mm all the way ( to the last T-off ) and then drop to 15mm > combi, then effectively you have enough capacity in the 22mm pipe to service the "theft" as well as still having sufficient residual capacity to provide adequate cold mains 'potential' at the combi. Any instant water heater should have "cold mains priority" which is either achieved by running a dedicated feed from the stopcock to the appliance, or by doubling the capacity of the single supply pipe.

[Nickfromwales]

Good idea with the fish top-up feed. Filling mine manually is a PITA !

[Super_Paulie]

2 hours ago, Nickfromwales said:

The flow rate at the combi boiler cold inlet is....

very interesting, thanks Nick, thats what i'll do.

In regards to the fish, hell yeah! the novelty wore off very quickly using buckets etc so i have a hot and cold feed that i mix with valves. Might get a TMV as an upgrade as the temperature always needs to be the same really. They double up as a syphon as well to drain the old tank water away via a pipe to a soak away outside and its an absolute lifesaver, can recommend.

[Super_Paulie]

Almost seems a crime to put this in a cupboard...

My plan is to change the copper tails to layflat, copper was just to keep my clips in alignment, so that it's just a continuous pipe with no joins to each appliance. Dedicated 22mm feed to the boiler.

1 spare on each, but room to add another 2 port to the ends if needed in the future.

 

Any suggestions of changes before I solder this up? (Feeds close to the main due to space limitations under the floor so I had to bunch them up to fit between joists and through the gaps in brick.)

 

As it's in the bunker with the ufh manifold I assume I'm going to have to lag up these colds to stop condensation @Nickfromwales?

 

 

Edited May 6, 2023 by Super_Paulie

[Nickfromwales]

Condensation will only be an issue if the surface vs ambient temps are a way apart. Maybe try it without lagging for a season, and lag if absolutely necessary?

 

I too consider it a crime to hide all my lovely plumbing, but it's a cross we each have to bear!  

[Super_Paulie]

Bit of a dilemma... Do I leave these tails copper (new cut, all the same length, obviously) and use an elbow under floor level to attach the plastic runs or do I take the plastic all the way up to the manifold. I was wanting to have zero joins but the copper is proper sexy to look at and it's shiny. Or am I just losing the plot here with visual over function.