3/4 o 1/2" water line?

I'm redoing the plumbing in our 1/2 bath (sink, toilet, and washing machine) and am going to have it go down the line and T off (copper line), where right now it goes the long way around, and the toilet is separate from the other 2. The line to the sink is 3/8 right now, and then the washing machine chokes down to 3/8 then back up to 1/2". It's a mess and I want to tidy things up a bit.

I've got 1/2" copper already, but wondering if I should go with 3/4 off the main line to the sink, then choke down to 1/2" or would 1/2 be enough for it all? Also making anti-hammer dampers where it branches out of the wall to the sink by putting in a T instead of an elbow, and capping off an 8" peice above it to trap air. The washing machine hookups had store bought water hammer dampers underneath in the basement, and if I can un-solder them I'll put them back on, otherwise I'll probably see about making some for that as well.

What say you?

Donovan from Wisconsin

When I replaced my old copper lines with plastic, the plumber working on my job at the time told me it's a good idea to run a bigger main to the branch lines.

I ran a 1" trunkline end to end of the house and branched off with 3/4" to all fixtures and put a ball valve on each branch.

It's the way to go, although granted it's much cheaper and easier with the pvc.

One problem with sink fixtures is that they are choked down so small it may not make much difference there.

If you had adequate flow and pressure with the 3/8 should be fine at 1/2. Moving to 3/4 would probably just be overkill if I am interpreting your description correctly.

The bigger you go, the longer it will take for hot water to reach
the sink. Just one more thing to consider.

My only concernis that I will be adding the 3rd line to the same branch, so it will be the sink and washing machine, plus the toilet that was previously separate.

The flow with 3/8 seemed fine before, so maybe I'm over thinking this and a 1/2 line feeding all 3 off the 3/4 main will be fine. In the end, I'll probably have 10 ft. less copper, if not more, than if I would run it the same way as the old. The more I can return at the end of the project, the better!!

Also trying to figure out what I think I'll need to purchase yet, as Menards 11% rebate sale ends on Saturday. I need to go pick up the new vanity that finally came in, and the tiles I'm putting down. Will need to purchase what I need for the install of the floor yet.

Donovan from Wisconsin

I believe code here calls for 3/4 if more than 2 lines off it.

Having endured a rent house when I was young and poor which
was half a military barracks with old cast iron water lines, too
small for the job such that when someone flushed the toilet and
you were in the shower you got scalded, I'll say that you can
never have too large a line. Now I live in the country and the line
is a long way from the house. You can't plumb with the same
size supply lines you used in the city.

On hot water velocity to a faucet, do as I did in the house I
designed and built myself: Put the HWH near the point of use.
My inlaws had their HWH in the garage and it was separate from
the house, same type of sub standard plumbing...iron pipe, rust,
scale, too small...took forever to get a hot bath or get the water
hot to wash dishes....can't imagine what part of the water bill
was just wasted water waiting for it to get hot.

My 2c,
Mark

If there"s no shower, then just run the 1/2". 3/4" is over twice as big, so it"s going to take over twice as long to get hot water there, meaning twice the wasted water. With a shower, it would be worth it because you would(should) never get scalded. Even then you"d only have to run the cold 3/4".

my 2cents
cold water
3/4 from main by the meter to 3/4 x 1/2 x 1/2 tee
then seperate 1/2 to toilet, 1/2 to washing machine and sink
hot water
1/2 is fine all the way
good luck

Ron

If you can afford it you will be surprised how much you would like one inch main cold and hot lines. At least in a large house. Especially if your in the shower down stairs and someone takes a dump up stairs. 3/4 main lines are good though.

3/4" everything. Prevents the shower from running cold or
scalding when somebody else uses water.

Distance matters. I would not run 1/2 inch water line more than about ten feet, even for a single tap. 1/2 inch pipe has less than half the cross-sectional area of 3/4, so you'll get as much pressure drop in ten feet of 1/2 inch as in 23 feet of 3/4.

I would use 3/4 for the cold to where it branches off, then 1/2. 1/2 should be fine for the hot, it will save a lot of energy and you will get hot water quicker.

To keep water using appliances from effecting each other, keep the main line large (3/4"). Then each appliance should get its own separated small branch line (1/2") a few feet long. The greater resistance in the branch lines will isolate the appliances from each other.

The pressure in the main line will stay almost constant because the pressure drops are all in the branch lines.

Cliff(VA)

WHen I built my house 12 years ago the well guy suggested 1" from well to house then 3/4 lines to silcocs and 3/4 lines to bath, kitch etc. with the short 1/2 lines to the faucets. Wonderful!!! lots of pressure plenty of water..

Well, I finally finished my plumbing project around midnight (Friday-Saturday) and so far so good. When I turned on the water I only had one leak so all in all I don't think that's too bad. I cut it out, put in new elbows, cleaned the solder off the pipe and redid it again.

I'm not sure how many joints I did, but I'd say it's close to 50 or better. Things were going great till I ran out of the solder I was using and went to a different brand. Those joints just weren't turning out at all. I made a quick run to the hardware store I got the original stuff and bought another small spool of it and a few more elbows.

I ended up continuing the 3/4 trunk line(cold water) to the first branch, then choked it down to 1/2" for the toilet and washer. The hot I kept at 1/2 because that's all the bigger the line was in the 1st place, plus it was choked down to 3/8 and fed both the sink and washer with 3/8. The cold did the exact same thing and the toilet had it's own branch line. The water heater is almost right under where I was working, so hot always was hot within a few seconds. Basically when you would wash your hands it was turning warm by the time you started to rinse your hands.

When I got back from my solder trip I realized I didn't leave enough room for the sinks drain pipe to snake out between the water supply and the furnace duct, so I just took out a bunch of fittings I had in there and rearranged it a bit. That set me back some just to redo it, but it looks good for an amature.

Tomorrow is electric I think...

Donovan from Wisconsin

Once it was all said & done