plumbing question

[Michael Weber]

I know there are several plumbing forums available but this is simple so I figured the users here could help:rolleyes::D. I'm getting ready to upgrade water lines in my house to PEX using a home run system. Every device will have a separate hot and cold line running back to a manifold. I'm thinking that for everything except tubs and showers a 3/8 diameter line will suffice. Tubs and showers would get 1/2. Sinks, commodes, dishwasher, clothes washer would be okay with 3/8 inch. I have some runs that will be quite long (2 story house) and want the smaller diameter to provide hot water more quickly. Does that sound right? Thanks, Mike

[John Lanciani]

If it were me I'd stay with all 1/2" just to make the installation quicker and simpler. I don't think the small savings in water or the few extra seconds waiting are worth the added complexity of having two sizes of everything (for the install and for long-term maintenance). If you haven't already, check out supplyhouse.com (formerly pexsupply.com) for your job. Much less expensive than the borgs...

[Mark Bolton]

We run all 1/2" and no 3/8". I cant say for sure but I dont think you would be satisfied with 3/8" if your runs are of any length. A house I just finished has some runs that are perhaps 60-70' from the manifold. Manifold is less than 5' of 1" copper from a Navien on demand water heater. If I recall correctly it was about 20 seconds for hot water to those longest runs. We didnt opt for re-circ because the customer is using that bath primarily as a guest bath so that amount of time for showers isnt too unreasonable.

I have personally never used 3/8" on a job so I cant say for sure but I will say there is a noticeable pressure drop on long runs with 1/2" and it would be substantially worse with 3/8". The reduction at the fitting will be the real crusher.

[Jay Jolliffe]

I plumbed my house the way your describing with manifolds & lines to all fixtures. I used 1/2 pex for everything except the water conditioner & furnace where 3/4 & 1'' copper was used. We also use an on demand water heater.

[Jim Matthews]

Be advised that PEX likes sweeping curves and straight runs.

Trying to get 90 degree corners without kinking the line can be difficult,
and adds expense. Have you run this stuff before?

There are some warnings out there about line formulations that are prone to
pinholes, and the aluminum jacketed versions are unwieldy for first time users.

[Brian Elfert]

The aluminum jacketed PEX is not normally used for potable water.

[Mark Bolton]

Be advised that PEX likes sweeping curves and straight runs.

Trying to get 90 degree corners without kinking the line can be difficult,
and adds expense. Have you run this stuff before?

There are some warnings out there about line formulations that are prone to
pinholes, and the aluminum jacketed versions are unwieldy for first time users.


Could you post the current information about pinholes? I was on the supply side of the pinhole issue WAY WAY back in the late 90's and into early 2000's but I havent read a single current account of pin holes in any of the newer products.

Not questioning your information but it wouldnt be fair to the product to toss out info that isnt accurate.

[Chris Padilla]

I just bought some 3/4" PEX (from supplyhouse.com formerly pexsupply.com) to put in a dedicated hot water return line (Grundfos pump) and I'll be using some sharkbite fittings here and there for various turns. I'm remodeling our master bathroom and I'll attach the line to the hot side for the shower. This is the longest hot water line in my house and I'll have access to it. I haven't heard anything about pinhole problems. I'm running the line through my attic so I'll be insulating it as well.

[Mark Bolton]

I haven't heard anything about pinhole problems

Of course don't know for sure but my gut feeling is the reference about pinholes has nothing to do with PEX but rather is confused with a MAJOR issue with quest tubing many years ago. This was a major affair at the time but is a 25 year old issue and not even remotely the same animal as PEX. In the area I was in suppliers had touted the product and it swept through large developments and apartment complexes/condos. When the failures hit it was a total disaster.

Hopefully Jim will clarify his claim.

[Erik Loza]

I know little about plumbing except to tell you that when we house remodeled a couple of years back (100% new plumbing all the way to the water meter...), the contractor used 1/2" PEX on everything. Zero issues with water pressure upstairs, even while running both shower heads simultaneously. We do have decent water pressure (50psi+) from the street, for what that's worth. My thinking was that from an install perspective, it's easier and simpler to keep everything one size.

Best of luck with your project.

Erik Loza
Minimax USA

[Tom M King]

In one really old house where we made runs up to the third floor, I put the PEX in plastic electrical conduit. I don't remember the size of the conduit, but it was maybe 1-1/2". We glued all the joints and the PEX went right in with the sweep elbows. An electrical "fish tape" was used to pull the 1/2" PEX. We glued all the joints in the conduit. The thinking was that we wanted no chance of any future water damage to the expensive, old work, and the pipe would be easily replaced 75 years in the future. If there would ever be a leak in the line, the water would run back out the bottom of the conduit under the house. I'd consider doing this in new construction in some situations.

Plastic conduit is cheap. We also up the refrigerant line, and condensate drain in plastic conduit from the third floor air handler.

[Chris Padilla]

In one really old house where we made runs up to the third floor, I put the PEX in plastic electrical conduit. I don't remember the size of the conduit, but it was maybe 1-1/2". We glued all the joints and the PEX went right in with the sweep elbows. An electrical "fish tape" was used to pull the 1/2" PEX. We glued all the joints in the conduit. The thinking was that we wanted no chance of any future water damage to the expensive, old work, and the pipe would be easily replaced 75 years in the future. If there would ever be a leak in the line, the water would run back out the bottom of the conduit under the house. I'd consider doing this in new construction in some situations.

Plastic conduit is cheap. We also up the refrigerant line, and condensate drain in plastic conduit from the third floor air handler.

I like the over-engineering there, Tom!! Bravo!!

[Malcolm Schweizer]

I recently bought a house and everything is run with 3/4" pipes. I added an on-demand hot water heater, and it takes a long time to clear the lines before the hot, so I would say go 1/2", which is what other homes I've lived in had, and there were no pressure or flow issues.

[Michael Weber]

I recently bought a house and everything is run with 3/4" pipes. I added an on-demand hot water heater, and it takes a long time to clear the lines before the hot, so I would say go 1/2", which is what other homes I've lived in had, and there were no pressure or flow issues.

Yes, you should. Someone thought they were doing themselves a favor by going 3/4 probably to avoid what they thought was a pressure drop issue. That's basically why I was asking about 3/8 instead of 1/2 for non critical things like bathroom sinks.

[Jay Jolliffe]

The gas on demand water heater I put in said to use 3/4" pipe....

[Brian Elfert]

The gas on demand water heater I put in said to use 3/4" pipe....

Yes, the feed to the water heater has to be 3/4", but the OP is asking about the feeds to individual fixtures. In a house completely plumbed with PEX there is usually a manifold often near the water heater. The manifold is connected to the water heater and the water supply by 3/4" pipe. PEX pipe is run in a home run fashion to each fixture in the house.

[Bob Vavricka]

I've had some experience with a pin hole in PEX at my daughters house. I don't know the date it was built, but within the last 10 years. She called me about a year ago about water coming from her garage and I found a pin hole leak where the line came out of the wall to her water heater. It was spraying a fine mist on the sheet rock and running down the wall in the garage. Since then she had a leak inside the wall by the water heater and I had to tear out sheet rock to get to it. It wasn't a pin hole, but a leak at a fitting in the wall. I checked her water pressure and it was a over 100 psi, so I advised her to have a pressure regulator put on at the meter, which she did. Her house is a slab on the ground construction, so I hope she doesn't get a pin hole leak under the slab.

[Chris Padilla]

Too high a water pressure can definitely cause problems with all sorts of fixtures and as you found, Bob, to joints as well. Hers is about DOUBLE what is about ideal so yeah, she definitely should have a pressure-reducer put in.

[Jim Becker]

PEX is no different than any other medium when it comes to sizing. Just like our dust collection system ductwork, you can only fit so much into a pipe...so for home plumbing, the most likely design would remain 3/4" for feed in front of the manifold and 1/2" out to the "stuff". It's probably more efficient and cost effective to stick with 1/2", rather than mixing sizes, too., especially if you are buying the connections and terminations in bulk.

[Brian Elfert]

New RVs are all plumbed with PEX. RV owners have had connections blow apart due to excessive water pressure at some RV parks. A lot of campers will carry a pressure regulator to put on the spigot before they hook up the water. 40 to 50 PSI is the number most will regulate the pressure at.

[C Scott McDonald]

I did my last house using up Uponor pex and it worked out sweet. I did use the manifold as I just followed the old polybutelene pipe. Uponor is the way to go for sure.

[Brian Elfert]

There are several different processes that manufacturers use to make PEX pipe. The PEX-A process makes PEX pipe that is very flexible. I have used PEX pipe that is both PEX-A and PEX-B, and PEX-A is way more flexible. I've been using Flair-It PEX piping for my converted bus. Personally, I would only use PEX-A pipe. I'm not partial to any one manufacturer.

[Roy Turbett]

Not all Pex is alike. The ProPex 1/2" fittings have are 1/2" inside diameter whereas the clip type fittings are 1/2" outside diameter. The disadvantage of the ProPex fitting is is you have to buy or rent the expander tool.

Here's a link that shows the new Milwaukee expander tool. I have one and love it.

https://www.youtube.com/watch?v=xZdUnGXh_A8

[Mark Bolton]

Not all Pex is alike. The ProPex 1/2" fittings have are 1/2" inside diameter whereas the clip type fittings are 1/2" outside diameter. The disadvantage of the ProPex fitting is is you have to buy or rent the expander tool.

Here's a link that shows the new Milwaukee expander tool. I have one and love it.

https://www.youtube.com/watch?v=xZdUnGXh_A8


The expanders are by far the way to go but youve got to be plumbing homes on a regular basis (weekly or even daily) to make them reasonable. We have been plumbing entire homes with crimp style fittings and have yet to encounter a length of run that suffers from the reduced fitting diameter at the end of the run. Your talking about two restrictions in length of run that at any point in history may have had numerous elbows, 45's, and tees, in it.

[Brian Elfert]

Not all Pex is alike. The ProPex 1/2" fittings have are 1/2" inside diameter whereas the clip type fittings are 1/2" outside diameter. The disadvantage of the ProPex fitting is is you have to buy or rent the expander tool.


Isn't the PEX tubing/pipe still basically the same? Isn't just the fitting different?

[Roy Turbett]

There are several different processes that manufacturers use to make PEX pipe. The PEX-A process makes PEX pipe that is very flexible. I have used PEX pipe that is both PEX-A and PEX-B, and PEX-A is way more flexible. I've been using Flair-It PEX piping for my converted bus. Personally, I would only use PEX-A pipe. I'm not partial to any one manufacturer.

Brian -

Not all Pex tubing is compatable with the expansion tool. Heres a link to a compatability chart.

http://www.supplyhouse.com/PEX-Tubing-516000

Roy

[Jason Roehl]

I guess I fail to see the benefit of the manifold system. A home run for each fixture means that no matter what you're doing, you have to wait for hot water. There was a time when house plumbing was done for efficiency, both in terms of the hot water usage, and reduced usage of pipe material. My house is an excellent example of that--all the sinks, toilets and showers are relatively centrally located, so there is very little pipe used, and hot water shows up quickly.

On top of that, with home runs, you could take a hot shower (after waiting for the hot water), then if you went to shave at the sink next to the shower, you'd have to wait all over again. But if you did the plumbing in an more traditional manner, maybe you'd run a 3/4" supply to the bathroom, then 1/2" branches to the fixtures. After the shower was run, the hot water would already be very near the sink in the 3/4" pipe. (You probably wouldn't even need the 3/4", but it would allow use of both the sink and the shower simultaneously without a noticeable pressure drop).

[Mark Bolton]

I guess I fail to see the benefit of the manifold system. A home run for each fixture means that no matter what you're doing, you have to wait for hot water. There was a time when house plumbing was done for efficiency, both in terms of the hot water usage, and reduced usage of pipe material. My house is an excellent example of that--all the sinks, toilets and showers are relatively centrally located, so there is very little pipe used, and hot water shows up quickly.

On top of that, with home runs, you could take a hot shower (after waiting for the hot water), then if you went to shave at the sink next to the shower, you'd have to wait all over again. But if you did the plumbing in an more traditional manner, maybe you'd run a 3/4" supply to the bathroom, then 1/2" branches to the fixtures. After the shower was run, the hot water would already be very near the sink in the 3/4" pipe. (You probably wouldn't even need the 3/4", but it would allow use of both the sink and the shower simultaneously without a noticeable pressure drop).

That's the way we do it when there are multiple demands, a distance from the manifold. We feed that zone and manifold at that location.

The savings of a manifold system is that in a traditional branch system you may have a 1" main running the center of the house branching to each fixture. When you need hot water you have to purge that entire main to get it. As you say, centrally locating is wise but doesn't always work out in reality.

The savings of water usage and domestic heating are well documented. The wait on a small pex line with reasonable runs is trivial and the water lost emptYing the line is virtually nothing (often times less that 1 gallon)

[Brian Elfert]

I believe the reason PEX is usually run from a manifold is labor savings and fewer joints. Since PEX is flexible it can be usually be installed all the way to the fixture in one piece. Less labor when you don't need to install fittings to go around obstacles. A plumber can hire just about anyone off the street to run the PEX and the plumber only has to do the connections at each end. Fewer fittings means less chances to leak. Yes, you use a lot more PEX pipe, but it is fairly inexpensive and a lot cheaper than copper.

New houses seem to mostly be PEX these days. I would be surprised to see one still done in copper.

[Mark Bolton]

Im not sure the labor is the reason for the home runs when using pex or at least it wasnt the original motivation. The entire technology is adapted from Europe and it is used there for efficiency of water consumption and domestic hot water heating. The home run system allows for much smaller conductors to be used so you are not purging and flushing large branching mains to supply water to a single fixture at the end of the line. If you think of an average large home having perhaps 40' (averaged) of branched main between the meter/hot water heater and the farthest fixture, when you factor in dillution of hot water, heat loss, and so on, you can have to purge a couple gallons out of the line to feed that distant fixture. That or install recirc. and have its inherant loss and cost of opperation. A branched main has to be sized in the event that multiple fixtures are open at the same time. So the main must be oversized. After you are done purging that line and the demand is met you have flooded that large main with the equivalent two gallons of water which youve paid to heat and now will go cold in the main to just be flushed again next time.

With pex/manifold/home run systems that same fixture may have only .25-.30 gallons of water between it and the hot water source. This meas that you flush 6-8x less water to get your hot water, and you leave 6-8x times less hot water in the line to cool. With the branch system you may have to heat 2 gallons of extra water every time you use water at the farthest fixture in addition to the two gallons of water that went down the drain (water and sewer bill) while you waited for the hot water in the first place. Thats throwing money away. Here in the US we worry about that less, but in Europe where they pay far more that we do (the actual costs I would say) for their utilities, as well as population densities, they are maximizing every step of the way with regards to efficiency. Its just smarter.

Ease of running it and absolutely with regards to the cost of copper now are major bonus' but everything I have ever seen and read since it started being brought here from europe 20+ years ago speaks to efficiency. My beef with it is the plastic and the environmental aspects but that said I have no factual data how it compares to copper environmentally but I will guarantee you its not favorable.

P.S. You wouldnt believe how many times I have seen plumbers running rigid pex just like they would a copper main. Running 1" rigid pex with step down tees, joints everywhere, 90 degree ells instead of using flex, its horrible to see. It looks absolutely terrible (usually plumbers are pretty meticulous about running things level and plumb, right angles to the building, and so on). The worst part is as has already been mentioned, unless your running an expander, the fittings are all a restriction, so I can only imagine at the end of one of these branched mains run with pex you may get a dribble.

I apprenticed in the plumbing trade and the guys I worked for were very nuts about things looking clean and crisp. That can be hard to do with pex but it can still look decent when its done. Most of our customers are in awe when they see the manifold and they absolutely love the fact that if they have an issue with any single side of a fixture they can simply turn that circuit off and not disrupt anything else.

[John Lanciani]

On top of that, with home runs, you could take a hot shower (after waiting for the hot water), then if you went to shave at the sink next to the shower, you'd have to wait all over again. But if you did the plumbing in an more traditional manner, maybe you'd run a 3/4" supply to the bathroom, then 1/2" branches to the fixtures. After the shower was run, the hot water would already be very near the sink in the 3/4" pipe. (You probably wouldn't even need the 3/4", but it would allow use of both the sink and the shower simultaneously without a noticeable pressure drop).


I shower once a day and I never shave but I wash my hands many times in a day (x number of people in the house) so I'm definitely not going to see your expected efficiency. A reasonable length of 1/2" pex purges very quickly compared to 3/4" copper. The other huge benefit to a manifold and homerun system is the ability to isolate one fixture without disrupting the water supply to all of the others.

[Jason Roehl]

I didn't suggest everything branching off one main, just to be clear. Rather, I would suggest a manifold that supplied rooms, not fixtures. If you're working on the bathroom sink, there's generally not a need for the shower and toilet to still work in that bathroom (unless it's the rare bird of a one-hole household, but those aren't typically new and plumbed with PEX).

[Peter Stahl]

I think with PEX you want Home Runs so there are no fittings buried. Failure at a fitting in way more likely than a tubing failure. Also a regulator would be a good idea with PEX to protect you from a pressure surge. I would Home Run smaller lines for sinks & toilets and put larger ones for tubs. I have copper now so I don't see any PEX in my near future. Just my 2 cents, I'm not a plumber & haven't stayed in a Holiday Inn either.