I am in the process of converting from a single sink to a double sink vanity in our bathroom.
The existing PEX B water lines under the vanity are 3/8 inch (inner diameter).
To supply the double sink, I will need to branch off the hot and cold water PEX lines for the two sinks.

My question is, is there any downside to increasing the size from 3/8 PEX B (existing lines in the floor) to 1/2 PEX B pipe, using a 3/8 to 1/2 PEX reducer fitting, to do the branch off to the two sink's faucet's? I don't anticipate the 1/2 PEX lines to the furthest faucet run will be more the two feet each for the cold water and hot water connections. The reason is that I have more options with 1/2 inch PEX fittings (elbows, T's, etc.) at the hardware store.

Thank you.

I believe this should be ok. So long as you use the proper fittings, I don't see any reason this should create any problems for you.

Thank you for the reply, I appreciate it.



Edited 1 times.

i'd use 1/2 x 1/2 x 3/8 tees.

do use 4 shutoffs as well

Thanks for the advice on the T's and plan to do 4 shutoffs. thanks.

@ packy


1/2 x 1/2 x 3/8 puts the 3/8 on the bull (side outlet)


? did you mean 1/2 x 3/8 x 1/2 ? [run-run-bull]



@ OP

good luck finding EITHER tee at the 'local hardware store'

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

[www.homedepot.com]

precisely

(ship to store = not in stack locally)

designed for feeding a 3/8 FROM 1/2


that was my point


a 1/2 x 3/8 x 1/2 would be preferable to ensure smooth laminar flow (or close to it)



==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Understand your distinction of the PEX Tee's 1/2 x 3/8 x 1/2. Appreciate your and Packy's help.

Do they make a 3/8" inlet dual shutoff valve with 3/8" outlets? If so that may be all you need instead of splitting/branching let the valve do the branching and provide separate controls for each lav sink connection. If such a valve is not available may be just an adapter from 1/2" PEX to 1/2" then a dual control valve to two 3/8 outlets?