Water pipe sizing

[Jackflash2017]

I live in a townhouse codo complex. There are 11 units that are fed off a 1" copper trunk line. That line is tied into a feed from the street of at least 2" diam. Visually looks to be 3" O.D. of material most likely iron or galvanized pipe. Anyways, in each of our units the 1" trunk line drops to 1/2" that runs to water heater and all faucets and fixtures in the unit. In my unit in particular I run it through a softener first. Question is, will I get better volume to supply by running 3/4" copper to water heater and leave rest 1/2" ? My pressure is between 70-80 psi in basement and main floor. In second story bath it can sometimes drop to 55 to 60 psi. There are certain periods of the day filling the tub takes longer and shower isnt as strong. I suspect from high demand of the other tenants. Thoughts and ideas on if increasing pipe diam will help or just a waste of labor and money.

Thanks

 

[Reach4]

You can get a showerhead with a flow regulator. If you don't have that already, that should even the flow.

Time to fill the bath varies? Does that really bother you?

 

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[Jadnashua]

Assuming that your internal pipes are copper...the copper institute calls for a maximum water velocity of NGT 8'/second on cold. On a 1/2" line, that's about 8gpm. They don't want more than 5'/sec with the hot line - that's closer to 4gpm. Exceed those velocities/volume and you can get louder pipes, turbulence, increased pressure drop along the length, and in worst-case situations, literal wear on the interior of the pipes. FWIW, a 3/4" line will support twice the volume with considerably less pressure drop.

 

[Jackflash2017]

Wow!, now that's great physics that I can understand. I'm going to look into having a contractor swap the 1 x 1/2 x1 tee on main trunk line to 1 x 3/4 x 1. Sweating this size tee and having a main trunk supply to whole condo complex shut down is too much pressure to do job right with no leaks! I can change out the rest of pipe in my unit at my leisure.

Thaks Jim

 

[Jadnashua]

Have him put in a new ball-valve shutoff, then, you'll have a positive shutoff and all the time you want! Multi-turn valves tend to not actually shut off completely after awhile.