Manifold system versus hot return system

[Nickfromwales]

3 hours ago, weslev said:

Thanks for the tips NFW.

🙌

[Thorfun]

1 hour ago, Nickfromwales said:

5 hours ago, weslev said:

Thanks for the tips NFW.

🙌

NSFW more like! 😂

[Nickfromwales]

18 minutes ago, Thorfun said:

NSFW more like! 😂

I know where you live.

 

[sharpener]

On 15/03/2024 at 10:07, JohnMo said:

 

There are two sizes, you just have to watch the head required, the small one is a very low head output.

 

 

Thanks for the heads up. But as you may recall my application is to stir the tank to improve the heat transfer with a small coil. There is 1.05m head at zero flow, and it will do 0.9m^3/hr at zero pressure which should be fine, I don't need it to turn the tank contents over every 20 mins, just keep it moving.

[JohnMo]

49 minutes ago, sharpener said:

 

Thanks for the heads up. But as you may recall my application is to stir the tank to improve the heat transfer with a small coil. There is 1.05m head at zero flow, and it will do 0.9m^3/hr at zero pressure which should be fine, I don't need it to turn the tank contents over every 20 mins, just keep it moving.

Mine, the smallest one copes with 15mm tube for 20m each way, so should have no problem stirring a tank.

[Duncan62]

Given the advice here, maybe a split HW manifold and HW return system is best?

Any obvious errors?

[JohnMo]

Think you are making it over complex. You have lots of big pipe going on, do you need 32 and 28mm in any house system?

 

Cold water I would just run a 15mm feed to each wet room from a central manifold. Then branch from there. With individual isolation to each feed 

 

Then if you hit water return circuit just do it to the longest run room. It will then preheat the whole manifold. Remember you need a check valve with the circulation pump.

 

Bring you mpmd pipe to a single stop cock first. Then to outside tap via an isolated tee. Then a whole house prv and onwards from there. Cold water supply to mixer taps needs to come the cold outlet on the UVC inlet group. If it doesn't you need a check valve on the hot water outlet to stop reverse flow.

 

Simplify.

[Duncan62]

17 hours ago, JohnMo said:

Think you are making it over complex. You have lots of big pipe going on, do you need 32 and 28mm in any house system?

 

32mm and 28mm was simply to preserve water pressure?

Maybe I can simplify to 22mm once inside - and only have to buy one size of pipe!

 

 

Quote

 

Cold water I would just run a 15mm feed to each wet room from a central manifold. Then branch from there. With individual isolation to each feed 

 

 

15mm to bath/shower and 10mm to toilet - will the smaller toilet supply pipe help avoid any hot shower moments if the toilet is flushed? (even though the shower will be pressure balancing of course)

This would free up space in the plant room and reduce the amount of pipe required. Will need to make the wet-room manifolds accessible.

 

 

17 hours ago, JohnMo said:

Remember you need a check valve with the circulation pump

Had meant to add that. thanks.

 

 

17 hours ago, JohnMo said:

Cold water supply to mixer taps needs to come the cold outlet on the UVC inlet group. If it doesn't you need a check valve on the hot water outlet to stop reverse flow

Honestly not sure what a "Cold outlet on the UVC inlet group" is. But if a NRV on the HW outlet fixes this, I'll add it.

 

Thanks!

[ChrisDL]

I was going to ask the same question as this topic. I was planning on running 22mm hot and cold to each (15m ish will be the furthest distance to bathrooms upstairs)  wet room/area of the property then branch down to 15mm for each element from a smaller manifold. Sounds like 10mm for toilets seems advisable.

 

Is there a recommendation or preference for using PEX or polybutylene pipe?

 

Many thanks.

[IanR]

18 hours ago, Duncan62 said:

Given the advice here, maybe a split HW manifold and HW return system is best?

 

Why not run all the hot service from a manifold(s) and put the return loop up to the manifold only. Keep the manifold(s) hot (controlled with presence sensing), then use the smallest pipes you can get away with to the supply. Works really well for me. 22mm to manifolds 15mm / 10mm to Showers / taps. Return loop 15mm.

 

To keep the runs as short as possible from the manifolds, I used 2 separate hot manifolds.

[Duncan62]

44 minutes ago, IanR said:

 

Why not run all the hot service from a manifold(s) and put the return loop up to the manifold only. Keep the manifold(s) hot (controlled with presence sensing), then use the smallest pipes you can get away with to the supply. Works really well for me. 22mm to manifolds 15mm / 10mm to Showers / taps. Return loop 15mm.

 

To keep the runs as short as possible from the manifolds, I used 2 separate hot manifolds.

 

Sounds interesting, any schematics so I can fully understand your setup please?

 

Just worried, given what @Nickfromwales has said before that a 22mm pipe will mean it'll take a long time to get HW at the tap as there is a large volume of cold to expel? (hence for the taps only: 10mm ring main - based on this suggestion)(further, 10mm chosen as I'm wanting to keep HW losses to a minimum, as there is a low volume of "wasted" water in the ring main).

[JohnMo]

2 hours ago, Duncan62 said:

32mm and 28mm was simply to preserve water pressure?

Maybe I can simplify to 22mm once inside - and only have to buy one size of pipe!

Have you measured it do you need to preserve it? You need to dynamic and static pressure.

 

2 hours ago, Duncan62 said:

15mm to bath/shower and 10mm to toilet - will the smaller toilet supply pipe help avoid any hot shower moments if the toilet is flushed

On an UVC it just doesn't occur. 

 

2 hours ago, Duncan62 said:

Cold outlet on the UVC inlet group"

First image I found - the valve that splits mains water supply.

 

2 hours ago, ChrisDL said:

running 22mm hot

No need. My hot water run is 16mm from UVC, 8m to hot water manifold the 16mm to each wet room longest another 8m then branched from there. By the time you get hot water you will have changed your mind about showering.

[IanR]

1 hour ago, Duncan62 said:

any schematics so I can fully understand your setup please?

Showing the hot service only:

 

1 hour ago, Duncan62 said:

Just worried, given what @Nickfromwales has said before that a 22mm pipe will mean it'll take a long time to get HW at the tap as there is a large volume of cold to expel?

 

Yes, but, the HW return is taking care of that, and with presence sensing reducing loses.

Edited July 3 by IanR

[Iceverge]

On 02/07/2024 at 16:18, Duncan62 said:

Given the advice here, maybe a split HW manifold and HW return system is best?

Any obvious errors?

 

Bigly complicated IMO. 

 

What is the length of run to your kitchen tap? Ours in 13m and takes about 10secs to hot at 5/6l/min from a convection heated 10mm pipe.  A good chunk of the volume of the dead leg is in the kitchen tap though. 

 

In any case, assuming you are using a mixer kitchen tap, my understanding is that you would need to feed the cold through the T&P valve to ensure a balanced flow so not teed off the mdpe individually. 

 

25mm MDPE to the stopcock, 22 mm Hep20 to the cylinder and then manifolds, 15mm for kitchen/utility taps + bath/showers and 10mm for everything else. 

 

Our 10mm gives roughly 5.5l/min, 15mm gives about 10l/min.

 

 

 

 

 

[Iceverge]

 

That was ours. 

 

I would have no issues teeing off inside a bathroom for a basin or w/c provided that the joint was easily accessed and ideally there was a floor drain somewhere to catch any leaks.

[Nickfromwales]

On 03/07/2024 at 13:12, JohnMo said:

On an UVC it just doesn't occur. 

It does (can) if the WC’s are sharing the balanced feed from the UVC multi block aka control group (PRedV). 
If the cold mains isn’t great, then I always recommend feeding the WC’s off the raw cold main, before any pressure reducing gets done. 

[Pocster]

3 hours ago, Nickfromwales said:

It does (can) if the WC’s are sharing the balanced feed from the UVC multi block aka control group (PRedV). 
If the cold mains isn’t great, then I always recommend feeding the WC’s off the raw cold main, before any pressure reducing gets done. 

I said this on page 1 but my post accidentally got deleted 

[JohnMo]

3 hours ago, Nickfromwales said:

It does (can) if the WC’s are sharing the balanced feed from the UVC multi block aka control group (PRedV). 
If the cold mains isn’t great, then I always recommend feeding the WC’s off the raw cold main, before any pressure reducing gets done. 

Maybe I am not suffering from that because I don't use the balanced from the UVC, but instead have prv after the stop cock then the cold manifold. But of the upstream of the stopcock I have a cold water accumulator fed by a borehole pump.

[Nickfromwales]

2 hours ago, JohnMo said:

Maybe I am not suffering from that because I don't use the balanced from the UVC, but instead have prv after the stop cock then the cold manifold. But of the upstream of the stopcock I have a cold water accumulator fed by a borehole pump.

Night and day different for your setup then.

[Iceverge]

Everything is downstream of the PRV for us and I notice no difference when showering no matter the draw on the cold.  We have a borehole so the pressure is as good as we want it.

 

Maybe the thermostatic shower takes care of any differential flow.