Home>Discussions>PLUMBING>What size Pex line to use???
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NickL
What size Pex line to use???
NickL

I am replacing the 60 year old copper plumbing in a ranch home and want to switch to Pex tubing. My plan is to run from the water meter to a manifold . Output of the manifold will be all 1/2 pex lines that will run to each area of demand. I have seen this set up referred to as "home run" manifolds. My question is the input to the home / water meter is 1" copper. On the output of the meter I will switch to Pex. All the manifolds I see are 1" copper with 3/4 pex fitting as the input. So is there any advantage to maintaining the 1" size from the meter to the manifold since the input fitting is 3/4. I'm not sure I will be taking advantage of the 1" pipe if it gets reduced to 3/4 at the manifold input. I have the same question on the hot water manifold. Do I come out of the indirect hot water tank with 1" or 3/4 to the manifold? Any help would be appreciated!

dj1
Re: What size Pex line to use???
dj1

From the meter to the house, run 1" copper TYPE L. Bury the pipe in 2" sand. PEX underground is too risky. Also, if PEX is exposed when entering the house, it will leak.
To make a transition from 1" to 3/4" - use a reducer.

NickL
Re: What size Pex line to use???
NickL

sorry for not being as clear as I should have. The meter is located in the basement. The town ran a 1" copper line from the street to the basement interior wall, where the water meter is located. So do I use a reducer at the output of the meter, or is there an advantage to maintain the 1" to the manifold?

dj1
Re: What size Pex line to use???
dj1

Quote: "The town ran a 1" copper line from the street to the basement interior wall, where the water meter is located."

In my city, the water dept doesn't provide a main line from the meter (at the street) to the house, and into the house. I doubt that your town does that.

Main line is the homeowner's responsibility. What you do for a main line is up to you, and your expense.

There are various factors to determine the size of your main line, such as number of faucets, baths, toilets, etc. However, if the original main line was 1", stay with that size. The advantage to keeping the 1" line is the "volume", in case 2 or more faucets are turned on at the same time.

dj1
Re: What size Pex line to use???
dj1

If you are not sure who's responsible for your main line, contact your water provider.

Let us know.

NickL
Re: What size Pex line to use???
NickL

Not sure whats gives you the impression the question revolves around the line from the street to the home...
My question was, If you have a 3/4 " pex fitting on a manifod made of 1" copper, is there an advantage to use 1" Pex to that fitting, or did any "volume" advantage disappear with the reduction to the 3/4" input to the manifold?

dj1
Re: What size Pex line to use???
dj1

What threw me off was the fact that your city provides the main line from the street to the basement. Question: do you have a pressure regulator valve (PRV) in the basement?

All right then, if you use a reducer from that 1" pipe to the manifold (3/4"), you won't see any volume reduction.

Mastercarpentry
Re: What size Pex line to use???
Mastercarpentry

The reducer fitting will restrict the flow to whatever it's smallest size is at that point. Since your 1" run is short I think 3/4" will do there but if it were longer I'd run 1" between. If it were me I'd seek a manifold that had a 1" inlet since even a 3/4" line may prove small under extreme water usage. My 'landlord' customer runs nothing bigger that 3/4" anywhere and when you turn several things on at the same time you get a noticeable drop in pressure and flow.

@dj1 can you expound on why not to use PEX underground? We've been doing that for about 6 years now and have had no problems yet. Sure beats the dead galvanized it replaces!

Phil

dj1
Re: What size Pex line to use???
dj1

@dj1 can you expound on why not to use PEX underground? We've been doing that for about 6 years now and have had no problems yet. Sure beats the dead galvanized it replaces!

Phil[/QUOTE]

- PEX may allow contamination through, subject to various conditions in the soil. I can see it being used indoor.
- PEX may not hold under extreme pressure. I have two rental properties on hillsides, where street pressure runs 150 to 200 PSI. Do you think I could trust PEX before it reaches the PRV?
- Studies about water safety in PEX are inconclusive, depending what reports you read and who wrote them. Why take a chance?

In my city PEX was approved just 2 or 3 years ago, yet very few plumbers who specialize in re-piping will install them, even though they are way cheaper than copper, easier and faster to install and don't require wall cutting as copper.

Yet PEX is so popular in other areas of the country.

Do you know why copper is so expensive? because it's worth it. And after working with copper for all these years, installing copper is a breeze.

Fencepost
Re: What size Pex line to use???
Fencepost

The city (or water provider) is responsible for the line to the meter. In the original poster's case, the meter is located inside the basement of the house rather than out by the curb. This is common in areas with deep frost.

The size of the pipe does matter for long runs. Due to turbulence within the pipe (even very smooth pipes like PEX and copper have turbulence), the larger diameter provides less resistance. Even though it will be narrowed down to 3/4" at the manifold, a long run of 3/4" pipe would provide lower pressure at a given flow rate (or a lower flow rate at a given pressure) than 1". However, since the distance between the meter and the manifold is relatively short -- probably less than 50 feet -- the difference in flow/pressure will be unnoticeable. Keep in mind that sharp bends (90s) also increase resistance comparable to dozens of feet of pipe.

As to the safety of PEX versus copper, the distrust of PEX is due to its chemical properties not being well understood by the general populace when compared to copper. The properties of copper are well known and understood. We tend to fear that which we do not understand, and trust that which we do understand. "Better the devil you know than the devil you don't." Certainly PEX is not without problems in certain conditions, but copper isn't perfect under all conditions, either. In certain types of water, PEX may be preferable because harmful copper compounds may develop. In general, though, PEX is more chemically inert than any metal except g0ld.

If you buy milk in plastic jugs or paper cartons, you are consuming food that is stored in contact with polyethylene, the basic chemical in PEX (cross-linked polyethylene). In fact, most food products -- even if not sold in polyethylene packaging at the supermarket -- have ingredients that are transported to and stored in food factories in polyethylene containers. Polyethylene is considered food-safe by the FDA. The cross-linking process of PEX makes it even more stable than HDPE. So avoiding polyethylene in your water piping will have the most minimal of minimal benefits, unless you grow all your food yourself.

Much of the distrust of PEX is actually due to other plastics which were marketed in the past but proved to be problematic. Polybutylene had a nasty habit of degrading over time (even when not exposed to sunlight) and blowing up. Polyvinyl chloride (PVC) may leach chemicals into water and becomes brittle over time, especially in sunlight. Polycarbonate (Lexan) at one time was manufactured with bisphenol-A (BPA) which proved to leach into hot liquids, and which was implicated in fetal and infant development issues. (Polyethylene/PEX does not contain BPA.) These and other problems with various plastics have created a general distrust of plastics, even though food-grade polyethylene has never played a part in those reports.

Polyethylene is not produced directly from crude oil. It is produced from natural gas or petroleum gas (propane).

It's your choice, really. Use whatever you and your budget are comfortable with.

keith3267
Re: What size Pex line to use???
keith3267

I'm going to jump in here because I don't see any right answers. You need two manifolds, not one. You need one for the cold water lines and one for the hot water lines. It may come as a single manifold with two halves and a 3/4" input for each half.

You run a 1" line from the meter to inside your house. You terminate it with a bullhead Tee. This tee has a 1" in the center and 3/4" outs at the top. One 3/4" line goes to your water heater, the other goes to the cold side of the manifold (or the cold water manifold). The 3/4" output of the water heater goes to the hot side of the manifold (or to the hot manifold).

http://www.lowes.com/pd_186031-137-CL611_4294822005__?productId=3504920&Ntt=tee+fitting&pl=1&currentURL=%3FNtt%3Dtee%2Bfitting%26page%3D1&facetInfo=

Since you usually have to buy PEX in long rolls, you can use copper or CPVC to the manifolds, then 1/2" PEX out.

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