Water entry splitting question

[Xav]

Hey guys,

I'm doing renovation in a apartment and there's the main water entry for the building that split there. I was wondering if I should change it for optimization or if I can keep it as it is.

Here's a diagram of how it's splitting.

As you can see the 3/4 pipe turns into 1/2 pipes for 4 apartments. Do you think this is okay ? No one complained up to now but 1 of the 4 apparents is not currently used. I would like to minimize pressure drop if possible.

Thanks for any advice

 

[phishfood]

1/2" pipe to serve a single unit is a bit small. 1/2" pipe to serve 2 units is severely undersized. As far as that goes, 3/4" is severely undersized for 4 units.

If you can, increase the size of the main to at least 1". Then run 3/4" as far as possible from there. That would be the minimum I would do.

 

[Xav]

1/2" pipe to serve a single unit is a bit small. 1/2" pipe to serve 2 units is severely undersized. As far as that goes, 3/4" is severely undersized for 4 units.

If you can, increase the size of the main to at least 1". Then run 3/4" as far as possible from there. That would be the minimum I would do.

Thanks for your answer. Does the change from 3/4 to 1/2 seems okay, would a configuration like this would improve what I have currently ?

the top one is my actual config and the lower one is what I think is better.

 

[LiQuId]

yes... better. still 3/4 is small for 4 units.

assuming each unit has 1 bathroom group, and a kitchen sink.

typically a 3/4 line is the minimum that will serve these fixtures and not cause a loss in flow.
as phishfood has said 1" would be far better and then split the 1" to 3/4 to feel each unit ( a manifold in each unit ) and run 1/2" lines to the fixtures from the manifold.

if you really do want to see the effect have everybody run the showers and kitchen sinks at once... 1/2... you will see the pressure change.... but remember, its NOT about pressure, its about GPM.

 

[Mr_David]

Use a 3/4 x 1/2 x 1/2 tee at the middle branch lines.

1" service to 3/4 to each unit would be better. But if 1/2 and 3/4 is what is already there. I've seen some old homes that only have a 1/2" service and they have survived.
If they complain just just tell them there are some really nice places for rent In Libya or Afghanistan.

 

[Xav]

Thanks a lot for all your input, I did what Mr_David proposed. Since I can't change all plumbing in other apartments right now. But if we redo the whole system I'll put 1 inch and 3/4" pipes as far as I can.