Incoming mains MDPE

[DaveH]

Evening all,

 

I have a 32mm MDPE supply with a Plasson stop tap on it coming into my plant/utility room. The supply comes in on the ground floor where the kitchen, utility and a WC are located. On the first floor is the master ensuite and another separate toilet and the main house bathroom is on the second floor. Just starting to think about my plumbing specification now and I'm planning to use copper rather than plastic but would you go for a branch or manifold plan? I'm leaning towards a traditional branch plan for the reasons below:

 

• One of the advantages of manifold plumbing used in a plastic system is the lack of hidden joints but that doesn't apply if I'm using copper
• Manifold system would be a higher material cost as I would need a lot more pipe
• However, pressure and temperature variations would be less with a manifold system

 

Which have you gone for and why? And would you go from 32mm MDPE into 28mm copper (I know the I/D are very similar) or straight down to 22mm?

 

Thanks

[Temp]

We have a bit of a mixed system. Everything to the left of the Thermal store is downstairs. The Store and manifolds are upstairs. The manifolds are located between the two bathrooms which are close together. So I think any extra pipe due to the use of a manifold approach was minimal. 

 

It's a mix of copper and plastic. Mostly 28mm copper before the manifolds and plastic in various sizes after. The manifolds were "home made" from 28mm copper fittings. The diagram is simplified (I've not shown the boiler loop, isolating valves and the Thermal Store is much more complicated). The water softener is just a place holder with bypass as we haven't needed one. One of our showers is a high flow rate with body jets. Works well.

 

 

 

 

 

 

[DaveH]

Thanks Temp

[Conor]

So my perspective as a water network engineer if I was considering this like a scalded down public water network...

 

32mm X 25mm X 25mm  tee on to your 32mm stopcock (the "reservoir" with a dual outlets). I'd then run a 22mm pipe (trunk main A) directly to the hot water cylinder.

 

It would also be worth teeing off another 22mm branch from the cold water pipe to supply all of your garden taps.

 

The other branch from the tee would also be 22mm and would run in the shortest route to the main bathroom/ furthest outlet. All other cold water feeds in the house would come off this "trunk main B" via 22x15mm tees. Each branch is a smaller diameter "distribution main". Only time I'd branch off a 15mm would be for a low demand feed such as a toilet cistern or wash basin. 

 

The same would be for the 22mm outlet from the hot water tank. You'd run this 22mm trinkmain to your main bathrooms for the showers and baths. You'd tee off a single 15mm pipe for the washbasin in each bathroom. Also same for the kitchen sink.

 

The trade off for larger hot water pipes is that the larger volume means it takes longer for hot water to reach the outlet compared to 15mm pipes. It's a balance between ensuring adequate flow and hot water readiness. Water age as we call it in the industry.