Redoing PEX that was incorrectly sized


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Old 09-14-21, 10:57 AM
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Redoing PEX that was incorrectly sized

Purchased a home on a well (well pressure is good) and owner prior to the last changed plumbing to PEX. Problem is they ran 1/2" from supply to everything so water pressure is non-existent. Upgrading the supply lines to 3/4" and have several questions.

Can the 1/2" to the water heater remain? Is there a product that meets code to insulate PEX as it is connected directly to the gas water heater or do they need to be changed out to copper 18" above connection? Right now they are wrapped in some form of insulated covering.

Almost all the corners are 90 degree sharkbite connectors, do those decrease pressure enough to be concerned or should they be replaced with longer runs of 1/2" and sweeping bends?

The PEX is run above the drop ceiling in basement so it connects directly back to the copper pipe leading to the bathroom and kitchen right at the floor line, thinking to leave those connections as is since only running new 3/4" supply. The way all the existing is run it goes from the water softener, runs up the wall and branches off in several directions towards the laundry room, bathroom and kitchen. To reroute everything would mean redoing the whole system and start from scratch. Any thought? Had a plumber come by and the way I am doing is what they had planned.

Thanks,
Any insight would be appreciated.
 
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Old 09-14-21, 12:41 PM
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Yes, 1/2" to the water heater can remain but it makes your plan to upgrade to 3/4" sorta useless as you are still limited by how much water can flow through a 1/2".

Yes, you can plumb PEX directly to the water heater.

A sweeping bend of PEX has less flow resistance than a 90 fitting.
 
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Old 09-14-21, 12:51 PM
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Okay, that was my thought also, I will upgrade the outlet from water heater to 3/4" and then branch off. Should the inlet also be 3/4" or will that matter? Probably will never drain the tank enough to be an issue, there is only 2 people and occasional family.
 
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Old 09-15-21, 05:13 AM
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Yes, the line feeding the water heater should be 3/4" if your lines after it are 3/4" otherwise the larger pipe size doesn't help.
 
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Old 09-16-21, 10:06 AM
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Before you start re-piping, I'd confirm that it is truly the 1/2" pipe that's causing you problems. I highly doubt it. I've lived in houses with 1/2" piping throughout, and the pressure/volume has always been quite sufficient, even with multiple fixtures running. I realize PEX has a smaller ID than copper, but in most normal-sized houses, it should be quite sufficient.

Of course, if you do re-plumb, I would recommend 3/4" for any main trunk lines including to and from the water heater. Then 1/2" for branches.

Lastly, code on PEX directly to water heaters is conflicting. UPC does not allow PEX for the first 18" into and out of the water heater, regardless if it's gas or electric. But most (all?) PEX manufacturers allow PEX directly connected to electric water heaters. So it falls into the "depends on your local AJH/inspector". Oh - and never PEX directly into a gas water heater.
 
 

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