On Monday, March 9, 2015 at 12:33:04 PM UTC-4, dpb wrote:
On 03/09/2015 9:30 AM, trader_4 wrote:
On Monday, March 9, 2015 at 10:05:22 AM UTC-4, dpb wrote:
On 03/09/2015 2:53 AM, gregz wrote:
wrote:
I got a bathroom. I'm adding a second downstairs right below. ...
...
Run from hot water tank 20-25 feet, and cold tap. Still going to use the
1/2 feed from regulator and hot water tank.
...

I think you'll be sorely dissatisfied by the result if there's any
possibility whatsoever the two are being used together. That line needs
to go to 3/4"...

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A big unstated factor is if the new bathroom is a full one, ie with
shower or tub, or just a half bath. Half bath, 1/2" would be fine.

I'd say "marginal"...

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I don't see why it's marginal. I have a 1/2 bath plumbed with 1/2" copper,
works perfectly. The tubing on the fixtures is down to just 3/8". What flow
rate do you think you need at a sink and toilet?