# Switch from 1/2" to 3/4" main water line?



## Bob Mariani (Dec 1, 2008)

If it still uses the 1/2" at any point then the flow rate of 1/2" is all you will ever get.


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## al's sewer (Apr 7, 2009)

Most states require a min. of 3/4 inch some require 1inch. depending on amount of fixtures. In your case since you have 3/4 from the meter it would be best to run it all the way into the house. I personally do not like to run more than 3 fixtures on a 1/2 line although some codes say you can run as much as seven.


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## majakdragon (Sep 16, 2006)

I agree that you need 3/4" main water supply, but you need the entire line to be 3/4" with no downsizing in it. I always run 3/4" for feeding 1/2" take-pffs to each fixture and the the shut-off valve reduces it to 3/8" at the fixture (except tub and showers).


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## RegeSullivan (Dec 8, 2006)

I agree all incoming water lines should be ¾ or 1 inch. However if you have a regulator in the system somewhere after the ½” run of copper changing even the entire run to ¾” may not make a difference if you are reducing the incoming water pressure significantly.

If you have an expansion tank in the system you can get a pretty good indication if changing to ¾” would be beneficial or not. Just put a pressure gauge in the system and have a few helpers opened a couple of faucets at the same time. The pressure will initially drop and stabilize. If the pressure drops again after it stabilizes for a few seconds upsizing the entire run of 1/2" to 3/4" will help. If it stays stable after the initial drop it would probably not make a difference going to ¾ or even 2” for that matter.

You can pick up a cheap gauge that simply connects to a hose bibb in the plumbing department at HD or Lowes for about $10.00.

Rege


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## SanDiegoGuy (Mar 29, 2009)

Thank you all for your expertise, I'll see what I can do about extending the 3/4" main from the meter. The big problem is that I can't get to where it switches from 3/4" to 1/2", it is under cement. I might have to re-route the main entirely. Thanks again, this is a terrific forum!


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## kenmac (Feb 26, 2009)

I would suggest you re- route from under the concrete.. If it's been there a long time. If the pipe in the concrete & isn't protected....You may have problems with leaks in the future


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## II Weeks (Jan 6, 2009)

> [Just put a pressure gauge in the system and have a few helpers opened a couple of faucets at the same time. The pressure will initially drop and stabilize. If the pressure drops again after it stabilizes for a few seconds upsizing the entire run of 1/2" to 3/4" will help. If it stays stable after the initial drop it would probably not make a difference going to ¾ or even 2” for that matter./QUOTE]
> 
> never heard that before. will have to try that. kinda makes sense. why bother if the pressure's the same. BUT let ma ask you this, you can have lets say 40 PSI from any size line but wouldnt you have more volume with a larger line?


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## kenmac (Feb 26, 2009)

Yes, you will have more volume with larger line


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## brokenknee (Dec 13, 2008)

II Weeks said:


> > [Just put a pressure gauge in the system and have a few helpers opened a couple of faucets at the same time. The pressure will initially drop and stabilize. If the pressure drops again after it stabilizes for a few seconds upsizing the entire run of 1/2" to 3/4" will help. If it stays stable after the initial drop it would probably not make a difference going to ¾ or even 2” for that matter./QUOTE]
> >
> > never heard that before. will have to try that. kinda makes sense. why bother if the pressure's the same. BUT let ma ask you this, you can have lets say 40 PSI from any size line but wouldnt you have more volume with a larger line?
> 
> ...


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## RegeSullivan (Dec 8, 2006)

Higher pressure in the 1/2" line can have the same flow as a 3/4" pipe at a lower pressure. Municipal water is usually higher pressure than what is recommended for residential plumbing. That is why many (most) homes have regulators set somewhere around 40 PSI. In my home the water comes in at 130 PSI. Also, check your water meter. There is a good chance it is 1/2". It might look like 3/4" but if it is threaded and looks like 3/4" is is probably 1/2".

Rege


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