Yet Another Question About Supply Line Size

[Jim the dude]

I am replacing old galvanized supply lines. I am hoping this is the easiest way to explain it...
The main into the house is 3/4. It exits the meter at 3/4, then converts to 1/2 copper for about 4 inches. Then connects to 3/4 galvanized all the way up to a few inches from the water heater, when it changes to 1/2 copper for a few inches then converts to 3/4 copper to the water heater which was replaced last year.

I can't replace the 1/2 copper by the water heater because of its weird location, which is why I think the water heater installer just worked with the 1/2 and went up to 3/4 copper with copper crimp fittings, instead of coming off the 3/4 galvanized with the 3/4 copper.

The run from the meter to the water heater is about 20 feet. Is it worth using 3/4 pex even though there is 1/2 copper at the start and the end of the run?

 

[wwhitney]

The run from the meter to the water heater is about 20 feet. Is it worth using 3/4 pex even though there is 1/2 copper at the start and the end of the run?

The resistance from sections of pipe is cumulative, it's not a situation of "smallest size controls". So yes, use 3/4" pex or 3/4" copper or 1" pex, depending on the total demand (since it's cold water; on the hot water side, oversizing leads to increased wait times for hot water, so is to be avoided).

Cheers, Wayne

 

[Sponsor]

 

[Jim the dude]

The resistance from sections of pipe is cumulative, it's not a situation of "smallest size controls". So yes, use 3/4" pex or 3/4" copper or 1" pex, depending on the total demand (since it's cold water; on the hot water side, oversizing leads to increased wait times for hot water, so is to be avoided).

Cheers, Wayne

So if I follow you,I should run 3/4 or 1 pex from the meter to the water heater, then 1/2 on the hot side to the fixtures, even though there are small sections of 1/2 copper on both ends?

 

[Ronnyvagh]

PEX offers advantages like durability and resistance to corrosion, and using a consistent size throughout the run can ensure better water flow. Although there are 1/2 copper connections at the start and end, transitioning to 3/4 PEX might provide more consistent water pressure and avoid potential bottlenecks. If you're concerned about the weird location near the water heater, it could be worth exploring drain camera inspection services. They can help assess the situation and provide insights into the existing pipes and any potential obstacles. Ultimately, it's a decision based on your specific needs and circumstances.

 

[Fitter30]

Pex tubing size is different than copper and steel its smaller. Copper and steel is by i.d. Pex is cts/ nominal. Here's a chart that shows the sizes and how much per hundred feet each size holds in gallons. 1/2" .92 3/4 1.83 gallons

PEX tubing technical specifications and general installation practices

Dimensional data, pressure ratings, pressure drop table, typical circuit lengths and other technical specifications of PEX tubing used in system sizing and calculations.

www.pexuniverse.com

 

[Jeff H Young]

the 20 foot from meter should not be 1/2 thats too small.
should be 3/4 going in and coming out of water heater minimum if you are having all home runs to water heater area on hot those can be 1/2