Advice on my plumbing design!

[cailadd]

Dear All,
I'm very excited to be converting a small bedroom into an upstairs bathroom in our first house! I've been looking through PlumbersForum for tips and tricks on pipes and units, and come up with my own design for the new bathroom. I'd be very grateful if the lovely members here can cast their professional eyes over the plan, and offer up any feedback (positive or negative!).

I'm thinking of going for PB pipes and a manifold system to control each mixer separately. Since there's 3 radiators upstairs, I'm also planning on having heating manifolds next to the hot-cold ones (all accessible through the stud wall). So hot-cold / heating PB pipes (22 mm) running to the manifolds (along ~9 m length pipework from the combi boiler in the groundfloor utility room to the new upstairs bathroom), and smaller 16 mm pipes from the manifolds to the radiators / mixers. There's no radiator in the bathroom, as an electric underfloor heating system will be the primary heat source. Many of the connections are different sizes, so will need adapters at most connection points.

Many thanks in advance, I'd be happy to share updates when the project is underway.

All the best,
CL

 

[Deleted member 120897]

I’m not as advanced on some on here, but why the hot and cold manifolds? It’s a Combi boiler. What is the current flow rate and pressure?

 

[ShaunCorbs]

Looks fine to me slight add would use 50mm waste pipe if combining the bath and shower also an aav shower tray end would be best also

UT I’m guessing there in wall taps and showers and no where for service valves etc

 

[oz-plumber]

Probably because the OP wants to wait 25minutes for hot water to come to his basin vanity sink.
If it were me I would run the shortest amount of pipe from the boiler to the basin.

With 22mm pipe to a manifold and then 16mm from the manifold to the basin sink, with the measurements provided, I would think that a lot of water would be wasted waiting for hot water at the basin.

Realistically, a time wait for hot water would be 30 plus seconds.
Wasted water waiting for hot water - probably 5 plus litres.

 

[SimonG]

Wheres the old bathroom? You keeping it?
Why manifolds?
Why 3/4" for hot and cold?
Why no radiator/towel rail? The electric underfloor wont be enough. Going to rip the floor up when it fails?
Why no individual wastes to bath and shower?
Made a building regs notification?

 

[Chuck]

What are you doing for ventilation? Have you thought about installing vapour barrier?

 

[cailadd]

I’m not as advanced on some on here, but why the hot and cold manifolds? It’s a Combi boiler. What is the current flow rate and pressure?

Hi UT - sorry for the slow reply. My account was blocked for some reason, seems to be working again now.

The hot-cold manifolds are useful for balancing all the outlets and isolating individual systems if needed (for repairs etc). Looked like a useful feature to have.

I checked the cold flow rate from the kitchen tap (nearest the mains), and it's 17.5 litre/min - so pretty good!

 

[cailadd]

Looks fine to me slight add would use 50mm waste pipe if combining the bath and shower also an aav shower tray end would be best also

UT I’m guessing there in wall taps and showers and no where for service valves etc

SC - thanks, great tips! I hadn't thought of adding an AAV. Though I didn't add the dimensions of the waste pipes, I was thinking 110 mm for the toilet, 32 mm for the sink, and 40 mm for the shower/bath. But will go up to 50 mm for the shower/bath if that's better.

Correct - the units will all be in the walls

 

[cailadd]

Probably because the OP wants to wait 25minutes for hot water to come to his basin vanity sink.
If it were me I would run the shortest amount of pipe from the boiler to the basin.

With 22mm pipe to a manifold and then 16mm from the manifold to the basin sink, with the measurements provided, I would think that a lot of water would be wasted waiting for hot water at the basin.

Realistically, a time wait for hot water would be 30 plus seconds.
Wasted water waiting for hot water - probably 5 plus litres.

Great point, and thanks for calculating the expected wait times... If I go with the manifold system, one option could be to have the manifolds beyond the stone wall. That space is an attic (pitched roof above the kitchen, accessible by a loft hatch). That way the connection to the sink is shorter

 

[cailadd]

Wheres the old bathroom? You keeping it?
Why manifolds?
Why 3/4" for hot and cold?
Why no radiator/towel rail? The electric underfloor wont be enough. Going to rip the floor up when it fails?
Why no individual wastes to bath and shower?
Made a building regs notification?

Thanks SG:

• the old bathroom is downstairs at the end of the kitchen. The plan is to turn this room into a utility room / downstairs toilet.
• the hot-cold manifolds to balance the outlets and isolate individual systems if needed.
• these were the dimensions of the manifolds I've seen for sale. Not sure what's best practice here though, whether or not to have the in/out of the manifolds match the diameter of the pipework, or if using adapters is fine?
• We're using a 200 w/m2 system that should act as the primary heat source, with a properly insulated floor. There's always the possibility of failure, but I guess that's true of the pipework too. The product has a lifetime warranty, so we're happy to go with it.
• I wasn't sure about this, actually. I thought it'd be neat to combine them, given they're in line. But maybe this is bad practice?
• Yup, in the workflow. I was going to finalise the desired designs before contacting our local council.

 

[cailadd]

What are you doing for ventilation? Have you thought about installing vapour barrier?

Thanks Chuck. Yup, we're installing an inline extractor fan. Air volume is 16m3, and regs say 4 air changes per hour (64 m3 / hr). Inline does 250 m3/ hr 😅

All the walls and floor will have fully waterproof and insulated cement board installed, which should do the trick?

 

[Ben-gee]

Sounds like you are on it.
I would just reiterate- it is far better to run each waste separately to the stack/ hopper/gully than to combine them.

 

[ShaunCorbs]

But if it’s the only option it’s one of them

 

[cailadd]

Sounds like you are on it.
I would just reiterate- it is far better to run each waste separately to the stack/ hopper/gully than to combine them.

Thanks BG! That's great to know. I'll have a look and see if that can be done, but I don't think it'll be a problem.

(thanks all for the amazing advice so far!)

 

[oz-plumber]

Thanks Chuck. Yup, we're installing an inline extractor fan. Air volume is 16m3, and regs say 4 air changes per hour (64 m3 / hr). Inline does 250 m3/ hr 😅

All the walls and floor will have fully waterproof and insulated cement board installed, which should do the trick?

Bathrooms with a shower are generally sized on 20 air changes and hour.
That's the way we size them anyway.

You'll get @ 15 air changes and hour with the fan you have, so probably borderline