Full Replumb: 1/2" Copper to 1.5" PEX A

[Matthew Martin]

Situation:
1974 House that had an addition placed in 2008.
Layout:
No basement fixtures
First floor: 1/2 bath, kitchen with dishwasher, washing machine, addition kitchen sink, bathroom sink and shower, 2 hose bibs on opposite sides of the house
Second floor: 1 full bath with shower, 1 with tub
Furthest run from the meter is 40-50ft (hose bib or addition shower) and the second floor is 15ft vertical over the water main.
36 Water Supply Fixture units. No high flow fixtures except for a standard tub.
3/4" water main
5/8" water meter with 1/2" NPT pipe
1/2" copper thereafter

Obviously, any time water is used in the house there's impact on other places in the house.

My proposed solution:
Upsize after the water meter to 1.5" PEX A trunk, which will run from the water main to the back of the house addition and up to the second floor. From those areas, run local branches in 1/2" PEX to each individual fixture. Upsize hot to 3/4" PEX A and run 1/2 PEX A home runs to each individual fixture.

This plan was formed after reading a glut of information on here and utilizing this tool:
https://terrylove.com/watersize.htm on the basis that 1.25" copper is roughly the equivalent of 1.5" PEX.

I'm pretty sure this plan is sound. I'm obviously trying to avoid the gross expense of upgrading the water main. Unless I'm totally off base the only thing I'm wondering is if it's be worthwhile to upgrade the fittings coming in and out of the water meter to accept 3/4" pipe so I will only need 1 adapter to upsize the fittings to 1.5". Of course there is a tamper band, so that would involve me notifying the water company and whatever that entails.

Any advice or tips would be greatly appreciated.

 

[Terry]

Bumping up to 1-1/2" PEX would help a lot especially if an expansion tank is involved to buffer things a bit.

For that short section though before branching off with the smaller PEX lines, it may be easier to solder in some larger copper. Even 1" copper would make a big difference.

 

[Sponsor]

 

[wwhitney]

Upsize after the water meter to 1.5" PEX A trunk, which will run from the water main to the back of the house addition and up to the second floor.

1-1/2" is probably overkill, have you done any pressure drop calculations? What's the design GPM?

Of course, if you find 1" PEX would be marginal, there's probably not that much more difficulty in running 1-1/2" instead of 1-1/4". 1" PEX is already fairly stiff, I imagine 1-1/2" would be quite hard to bend and would require a very large radius, so you may need to use elbows for changes of direction.

I'm wondering is if it's be worthwhile to upgrade the fittings coming in and out of the water meter to accept 3/4" pipe so I will only need 1 adapter to upsize the fittings to 1.5".

It would be helpful to upgrade to a 3/4" meter, but the benefit to changing the nipples on the 5/8" meter to 3/4" pipe would be pretty small (see calculation below).

Not sure what you mean by "only need one adapter," looks like for a male adapter for 1-1/2" PEX you are restricted to 1-1/2" MIP, but you can get a 1/2" x 1-1/2" brass coupling to connect to your 1/2" brass nipple. [But would it be wise to put a ball valve with drain right after the meter? Maybe 1".]

Cheers, Wayne

Calculation: 1/2" schedule 40 is 0.622" ID, and 1-1/2" PEX is 1.263. That is a diameter ratio of 2, so if the smoothness coefficients are the same, the ratio of (pressure drop per unit length ) is 2^4.87 = 29 (Hazen Williams equation). While 3/4" schedule 40 has an ID of 0.824", an ID ratio with 1-1/2" PEX of 1.53, and a pressure drop ratio of 8.

But how long are those nipples? If they are 3" long, each 1/2" nipple is equivalent to 7' of 1-1/2" PEX. If you upsize them to 3/4" schedule 40, they would instead be equivalent to 2' of 1-1/2" PEX. So the net benefit would be the same as making your 1-1/2" PEX trunk line 10' shorter.

 

[Reach4]

Upsize after the water meter to 1.5" PEX A trunk, which will run from the water main to the back of the house addition and up to the second floor.

How long is that run?

 

[Jeff H Young]

Most residential work like this I do off the seat of my pants. this no exception. appreciate Wayne deep thought I need to get back to figuring a little better. Comparing 3 inches of 1/2 inch to 7 foot of 1 1/2" total 14 foot still suggests Your good to go! I wouldn't even stress the meter , Obviously a bigger main coming in and bigger meter , or at least a bigger main should have been run originally. But I think you got no problems if you ever decide to run new main address it then.

 

[Reach4]

Going to 1.5 inch PEX from the basement to the second floor seems like overkill to me. 1 inch PEX would be pretty low loss for a house.

If using stainless clamps, you would not even need a new tool for 1 inch. I am not a pro.

 

[Jeff H Young]

Going to 1.5 inch pex from the basement to the second floor seems like overkill to me. 1 inch pex would be pretty low loss for a house.

If using stainless clamps, you would not even need a new tool for 1 inch. I am not a pro.

I was thinking that too ! but I guess pex sucks when it comes to the ID of fittings

 

[Reach4]

I was thinking that too ! but I guess pex sucks when it comes to the ID of fittings

Less so for the brass fittings with clamp or crimp. But even for the fittings being smaller, 1 inch PEX is such an upgrade anyway. It seems a shame to buy a 100 ft roll of 1.5 and a new tool.

I just noticed the title says "PEX A". The F1960 type are bigger. If Mathew is using that, 1 inch fittings are not so restrictive. An expander tool for 1.5 is expensive. My manual expander tool only goes to 1 inch, and I have not had occasion to use that. If I ever replace my well pressure tank, I am thinking I will use some 1 inch.

 

[wwhitney]

Some data from Uponor's pressure loss tables, for water at 60F, psi pressure drop / 100ft:

GPM / 1" / 1.25" / 1.5"
5 / 1.99 / 0.72 / 0.42 (5.68 GPM)
10 / 6.54 / 2.53 / 1.18
15 / 13.58 / 5.1 / 2.37
20 / 22.44 / 8.65 / 3.9
25 / * / 12.75 / 5.76
30 / * /17.84 / 7.93

* means the flow rate exceeds the maximum recommended 12 ft/sec velocity.

So depending on length and design flow, 1" might be too small. E.g. with 100 ft trunk length and 20 GPM flow, 1.25 or 1.5 would be better.

Cheers, Wayne

 

[Reach4]

So depending on length and design flow, 1" might be too small. E.g. with 100 ft trunk length and 20 GPM flow, 1.25 or 1.5 would be better.

Few people ever exceed 10 gpm for a house.

Putting a tee at the output of the meter, and running separate paths to the outdoor spigots could make sure that the PEX to the second floor never be carrying the outdoor load. This would also be a good time to arrange plumbing for a future softener, and to consider a whole house cartridge filter for the house water.

 

[wwhitney]

Putting a tee at the output of the meter, and running separate paths to the outdoor spigots could make sure that the PEX to the second floor never be carrying the outdoor load.

That's a very good idea. Running (2) 1" PEX lines may well be easier than running a 1-1/2" PEX line. And not require the acquisition of a larger tool size for the 1-1/2" PEX.

Cheers, Wayne

 

[Jeff H Young]

Certainly another option Reach 4 came up with and a good one at that. Running 2 1 inch lines could help a lot and he could put more than just the bibs on one line . if he decides on a softener or whole house filter splitting the system be a good idea too.
If he has no acess to a tool that would be a factor as well

 

[Matthew Martin]

Thanks for all the replies. Sorry for the lack of response as it has been a crazy busy day.

In terms of expense, I have already purchased the Milwaukee M18 tool with expanders : 1/2-1-1/2. I got a good deal on it used. I know that 1-1/2" is a little more expensive and difficult to work with, but I'm guessing the workload won't be too crazy by comparison. The lack of available 1-1/2 manifolds is slightly annoying, but I guess I'll be downsizing to 1" to feed the local trunk manifolds.

Seems like my plan is relatively solid. I wanted enough volume that if I have or want to upgrade the main, I'll be good to go.

Of course there are many ways to skin a cat, but I didn't want to cheap out over the "should be good enough" option and have it backfire over a few hundred dollars.

 

[Jeff H Young]

Thanks for all the replies. Sorry for the lack of response as it has been a crazy busy day.

In terms of expense, I have already purchased the Milwaukee M18 tool with expanders : 1/2-1-1/2. I got a good deal on it used. I know that 1-1/2" is a little more expensive and difficult to work with, but I'm guessing the workload won't be too crazy by comparison. The lack of available 1-1/2 manifolds is slightly annoying, but I guess I'll be downsizing to 1" to feed the local trunk manifolds.

Seems like my plan is relatively solid. I wanted enough volume that if I have or want to upgrade the main, I'll be good to go.

Of course there are many ways to skin a cat, but I didn't want to cheap out over the "should be good enough" option and have it backfire over a few hundred dollars.

thats great you have the expander allready. yes solid plan

 

[Matthew Martin]

Just wanted to follow up on this. Completed this job in 2.5-3 days. Nothing to hard from someone who has minimal plumbing experience. Only had to cut holes in one wall.
Everything works great, would highly recommend PEX A. Job cost around $1250 excluding the tool and water heater and solved the flow issues.

If you're planning on running 1.5" PEX, I wouldn't count on not using 90 degrees unless you can figure out a way to deal with the force of the pipe flexing.

 

[Jeff H Young]

Glad Project worked out well! Dont follow you on the use of 90s?