How to Size Your Water Lines (PEX & Copper)

[@willplumb]

This is our first video that uses so many charts and diagrams - did you find our illustrations helpful? What can we do better for future videos? Thanks for watching!

[@willplumb]

@Christ Lucca Good! Appreciate the feedback.

[@joelprestamo9074]

Very helpful thank you! What about if you are using a manifold, I've been looking to buy one and they are pretty much 3/4" or 1" inlet for hot and cold and then 1/2" going to all fixtures...

[@willplumb]

@@joelprestamo9074 Joel, what you are describing is called a parallel water distribution system that uses a manifold. There are two types of manifold systems: + The “home run” system utilizes a centrally located manifold to individually distribute supply lines to each fixture. + The “remote manifold” system utilizes a trunk or main, which services several small manifolds that in turn service a group of individual fixtures. Which system are you thinking about?

[@joelprestamo9074]

@@willplumb I am thinking about the home run system.

[@willplumb]

@@joelprestamo9074 Joel, you would pivot to size based on GPM for the demand of all outlets supplied. Check with your local code but it will be somewhere around: 1/2" - GPM: Velocity at 4 ft./sec. = 2. Velocity at 8 ft./sec. = 5 3/4" - GPM: Velocity at 4 ft./sec. = 6. Velocity at 8 ft./sec. = 11 1" - GPM: Velocity at 4 ft./sec. = 10. Velocity at 8 ft./sec. = 20 1 1/4" - GPM: Velocity at 4 ft./sec. = 15. Velocity at 8 ft./sec. = 31 1 1/2" - GPM: Velocity at 4 ft./sec. = 22. Velocity at 8 ft./sec. = 44 Pros of a Home Run system: + Being able to turn off one circuit to make repairs without shutting down water to the whole house + Leaks are usually located at the manifold rather than out in the distribution piping. Cons: +Really hard to have a hot water recirc. This causes you to wait for hot water. +Wayyyyy more pex piping you need to buy. In summary, it's good for small houses with a centrally-located access to the manifold, bad for large houses that want instant hot water. I usually recommend trunk and branch systems as opposed to a manifold system. Hope that helps!

[@tomrufo3103]

Hey- this is like the most beautifully put together and well produced educational/informative home improvement video Ive ever seen in KZbin or otherwise. Someone get this guy a full time job doing this.

[@willplumb]

Thanks, Tom! I appreciate the high praise!

[@user-zo8tu3rl4i]

Can’t say less what a master..

[@beglitchery]

planning on replumbing my 130 yr old home. This is immensely helpful thank you

[@donp2474]

So am I. 135yr old house.

[@nobodynobody6216]

Wow, you are a life saver. Taking a plumbing class on line and your explanation is pure GOLD. You explain so thoroughly. It has helped me a lot. You are a master teacher. Thank you, thank you!!!!

[@chrisboyd4433]

Remember that this is finding the "minimum" allowed size. You can definitely upsize for more flow. I run at least 3/4" automatically from the water heater all the way to the end of the line and branch off to each fixture with 1/2" .

[@SP30305ATL]

You can definitely upsize for more flow, but for hot water you also want to consider that the larger the pipe, the longer you have to run the tap to get hot water which is both a daily (or more) annoyance and a waste of water. You could reduce this issue with a recirculating pump setup, but then it still increases your water heater load. A length of 3/4" pipe contains more than twice the water of the same length of 1/2", so you'll stand around approximately twice as long to get hot water to come out and you'll waste twice as much water. For cold water it doesn't really matter other than material costs.

[@ryankramer]

Wouldn’t oversizing it make you more prone to pressure drops elsewhere when both run at the same time? “Hey, look at this awesome water pressure when only one is running!” (Add three running at once) “Oh… this is not as cool.”

[@Knewman7777]

@Ryan Kramer this is just a guess, but the larger pipe should maintain higher pressure because the water can flow slower through it and still maintain the volume of water being poured from the various openings. If it follows Bernoulli's Principle, then a faster flowing liquid will produce less outward pressure on its container, while a slower moving fluid produces more. That should make a smaller line more prone to reduced pressure when multiple valves are open.

[@Bound4Earth]

​@@ryankramer I helped replace all of the water lines in my parents house from galvanized to 3/4 -1 inch cooper all the way through the basement, changing near where it heads up to fixtures. They recently had to install a new bathroom and I wasn't available so they called a plumber to do it, he chose poorly and used 1/2 inch for the cold water lines. Now they cannot use that shower and any other water fixture in the house or they get burned if someone uses any cold water. The 1/2 inch water lines shouldn't be that bad, so maybe he fucked up the soldering to much and partially obstructed the pipes or connected it farther away then he should have and flow is extra poor? I haven't had time to check on it so I can try to unfuck his disaster, but either way you have to size your pipes properly.

[@crystalburnham9757]

@@Bound4Earth THIS this is what I'm worried about-- scalding my future tenant if they happen to be showering when I decide to water the gardens. Any advice for me-- I want to put in 2 sillcocks-- there is no exisiting way to water the gardens I am starting in my (new to me) 1890's duplex. Should I tee in before the first fixture lines (1st floor shower) or just after? I'm guessing after (distal to). And do I keep same size-- 3/4 before splitting it to 1/2 and 1/2 for the north side and south side sillcocks?

[@alwoolhouse6255]

What a superb, clear, professional presentation. I am just about to plumb an entire off-grid farmhouse with three kitchens & two bathrooms. This was extremely helpful. Thanks.

[@djanes302]

I love the video and it came at a perfect time for me. I'm sure a lot of people would like to see more videos like this. There really isn't a lot out there explaining how people go about sizing stuff up for their house if they're doing it themselves.

[@willplumb]

This comment is music to my ears. Real happy that this helped you out!

[@grovesville]

I'm an old San Francisco local 38 plumber. Cast iron and copper was the norm there. I did a 4" copper waste (Exposed below) and vent system for the telephone company. Priceless. Nice video and I'm sure you're a top notch plumber. I was! ;-))

[@TerriCull]

Best explanation ever! Thank you so much. I have probably just gotten "lucky" sizing plumbing on rehabs in the past. Now I know I'll be doing the right way!

[@gypsetsalon2585]

Awesome as a remodeler I’ve been doing plumbing for yrs and used standard configuration I run the mains as 3/4 then to 1/2. This really opened my eyes to the calculations really needed. Thanx very helpful video

[@samwilliams1024]

Super Helpful THANKS!! As a DIYer it's nice to have a comprehensive how to video and Sweet diagrams!

[@robertjackson7590]

Excellent video on the whole house plumbing.... Someone installed PEX B at this main coming into the house in a repair but bc you'll never see all the fixtures on at the same time the customer never knew it was done. 99.9% of the time it'll never move 22.25GPM through that point. Copper crimp with no tape/protection buried in the ground. Thanks again for taking the time and the videographers effort. subbed.

[@gecko2345]

A great description of the process. The repetition just illustrates the detail needed to get an accurate need. Thank you for this video.

[@garytabasco17]

These videos are excellent. I am a property maintenance supervisor, and pretty good at it, but I am a Jack of all trades, master of none. It is great to find informational videos that will grow my skill set, and yet are also very entertaining.

[@MrPerrisin91]

I am now a subscriber bro! I’m new to rough in plumbing about a month in and I just about got about all the 3rd&4th guy stuff down backings, scabs, setting tubs, drilling backings, ford fittings for service etc. today when I was in the crawl I had to help the 2nd guy (water piper) tee in some lines and I’m laughing because I think I had that ah ha moment like “oh shit I know how this goes now” anyways dude your video confirmed it and explained so much to me that I felt like I already knew and I’m gonna re watch this video over and over, I’m soooo excited. Love from Seattle!! 💪🏾

[@wyleaziz5050]

I know now why you said "your favorite plumber". I can not thank you enough for removing such a huuuuge burden regarding pipe sizing and pressure drop. Could you please make a video on how to select the size of the Water heater ( heating element selection) & Water storage tank.. God Bless!

[@cju4300]

Very well presented. It takes a lot of work to create videos like this. Thank you.

[@willplumb]

Yes, it does! Thank you for watching, and I hope this helped!

[@easeyyy1800]

I’m a second year student at PHCC and HOLY SHIT this video took a huuuuuge burden off my back. Thank you, keep up the great work and god bless man 🙏🏽

[@willplumb]

That’s awesome to hear. Happy to help!

[@jamiedyercville]

As a Harry Homeowner, this is very helpful information presented in a clear manner. Just what I needed. I'll pass it around. PS - Your artwork is perfect for the task. You should sign it. :)

[@richardhy6931]

A lot goes into these choices. Code is a minimum as you stated, but local codes will also come into play as well as manufacturers recommendations for their faucets (ie.. Grohe brand calls for 3/4” feed on most of their products) which is why you want to have your fixtures picked out before mechanicals are installed so tradesmen know what to prepare for.

[@FiliAinuu]

that was one of the easiest lesson i've had online great lesson thanks guys

[@willplumb]

Great to hear! Happy to help.

[@philipsanders5911]

Nice video. I would suggest adding to the total developed length based on the number of fittings in the system as required by code. The simple method is to add 1.2 feet per fitting. The ICC Codes also require the distance from water main to the meter be add to total developed length. Friction loss through the water meter or any special fixture such as backflow preventer, water softener or pressure reducing valve.

[@jackt6112]

Tremendously useful. I have galvanized that I'm replacing. Using your information I learned that it is sized well so I can just repeat what I have.

[@willplumb]

That’s great to hear, Jack. Good luck on your plumbing project!

[@Vincerama]

I'm thinking of doing the same thing, but probably using Pex B so I wonder if simply duplicating the galvanized without upscaling would work. On the other hand, the inside of my ancient galvanized pipes is probably clogged to the point that anything is better and even the pex b fixtures would be an improvement!

[@rnrjunkie724]

"Awesome" presentation! So easy to understand that an accountant can get it! Thank you

[@RayNewland]

Thank you! This was enormously helpful. I really appreciate you walking through the math with us.

[@jtkilroy]

Very helpful, and timely, thanks for putting in that effort

[@tomparrish6707]

Informative illustrations which clearly showed the calculation and fixture stack-up process when sizing water lines. I feel compelled to verify what is in my home before I start two bathroom renovations. Helpful explanation at the end of your video regarding Pex B flow restriction and when to consider sizing up. Would be curious to see some content on the potential issues of not having the lines sized properly. Great work!

[@willplumb]

Glad it was helpful!

[@madarain]

Very useful for me. About to run pex in a new house and had not considered this much. Glad I watched this particlular video.

[@Sean-tc7jm]

Great video! I wish you would have described how to measure the water pressure though. Total novice to that element and your explanations are amazing.

[@OneYulaw]

This is absolutely brilliant and so well put together. Thank you!

[@nobodynobody6216]

Thank you. Love your pictorial diagrams. Really helps the mind to internalize visual with your word description.

[@tsuyoikuma1400]

As an industry pro I found this video so helpful. Sometimes I forget why I do things that are just by memory. I would love to have this diagram as a poster in my home office. If I can’t get one screen shots will have to do

[@sail1999]

Best presentation I've seen no far.

[@Bound4Earth]

When I checked out my brother's rental properly I was shocked to see it was all individual 1/4 inch pex tubing. One big line into 20 in the basement branching off in every direction. It looked terrible and the main ran up an outside wall right before it split, so all of the lines would freeze in the winter. More plumbers need to watch this video, especially with Pex being much easier to work with and not having to think as much. Some just turn off the brain completely. To be fair this was nearly a decade ago, so it might be better researched now.

[@raakmore4443]

3/4 to the last branch for residential homes is a good rule of thumb to pass inspection

[@dmgsky5592]

Thank you for posting this - I am/will use to size my house repiping job.

[@PlumbingExplained]

great video buddy, was just explaining this to a young up and comer, gonna just share your video next time.

[@willplumb]

Awesome thank you!

[@Ayjayefff]

I’d be incredibly interested in how to plan for a water filter or multiple types of filters after your main and it’s impact on the math/flow here. Planning on replumbing my 70’s house and this info has been amazing. Thank you!

[@wadp7741]

Love your video. Please do a sample of sizing water supply for public restroom.

[@cmsgtluna]

Nice video and very informative for the average DIYer. You should do one more complicated, one that includes multiple hose bibs and lawn sprinklers and 3/4” fill valves, multiple shower heads etc.

[@willplumb]

Thanks for the idea!

[@econcep]

Quinn, this is fantastic! As a DIYer this information is invaluable, much thanks for putting this out!

[@marcoliviercaron5932]

This has to be among the best, most informative and useful video I have seen, like ever. Nice work!

[@donnaclayton8644]

Fascinating. My house has been size wrong in multiple places.

[@balloney2175]

A must for DIYers and of course, plumbers.

[@greasezert2228]

I ran 3/4" pex every where. No need to buy 1/2 when I all ready have 3/4". No different fittings. Worked great.

[@ridkwngridken3863]

ofc it did you, but its more expensive , use ur brain

[@greasezert2228]

@@ridkwngridken3863 not when you buy bulk and all ready have them. use your brain. i was going to run for president against joe and they said I was WAY overqualified.

[@ridkwngridken3863]

@@greasezert2228 thats special case, 99 percent people dont have then and dont hva bulk

[@prohomeworks1]

Very helpful. I am starting a diy repipe and I needed to learn about pipe sizing. I am making my own plumbing out line and using you guide. Thanks man!

[@willplumb]

Hey, good luck on the repipe project! Glad this helped!

[@westonwaterson960]

This is awesome. Through and explained very well. Thanks

[@user-dx7ky6qc4v]

Here in Mich a 2 family flat has a 3 quarter water meter.we run 3quarter then half at each fixture.if running pex with the insert fittings I just run 3quarter to the fixture and use a 3quarter to half adapter at the fixtures.good video taking the time to teach and share

[@Deep_Divers]

Exactly what I was looking for. Thanks!

[@spaceapproval6823]

That was really a great video and explanation amazing work. It wasn't what i was looking for as my problem was going from copper to pex but this did explain how increasing water pressure can help get adequate amount of pressure in a different way as well explain why homes are starting to get 1" lines.

[@ironmatic1]

Also interesting to note, 1" pipe, along with a 3/4" or preferably 1" meter is absolutely necessary to allow for a fire sprinkler system. Preferably at time of construction but also just to allow retrofit without digging up the yard. Pretty much impossible to make a 2 head NFPA 13D calc work with a 3/4" private main and 5/8" meter.

[@slippinslidewayz]

I'm installing a manifold system. Starting at the meter 3/4" runs to the hot water heater, back to the manifold, then branches off with 1/2" lines running for each appliance. Since I'm not replumbing the one bathroom yet, that system all runs on a single 1/2" branch as it did before, but that will be upgraded in due time.

[@IsraelUgarte1990]

Love the info and videos, I am not a plumber but these videos intrigue me and provide great info on the way installations work. I love DIY projects and learning about all trades so this info is GREAT! I do have one question...How is the pressure increased in a home. Reason is my parents are looking to build a home out in the country and I am curious on how water pressure is maintained at city supplied water pressure, if they getting water from a well? Is there a pump inside the home that regulates water pressure received upon use of each fixture? how does that work? the home will be a ranch one story home on a hill, where the garage and pressure tank will be on below the home. Should the Pressure tank be installed on the roof to have gravity assist with pressure?

[@KD-mz5xv]

i wish you were my teacher. great work.

[@SawtoothWild]

Extremely informative video!! But I have a ton of questions now.... Please make a separate video maybe? First, why is sizing to this level of detail so important? What would happen good/bad if not sized this way? What is the pros/cons to, say, run 1/2" from your meter and end up with 1" at your fixtures? What is water hammer and how to size pipe to prevent it? How to size pipe to prevent being scalded if someone flushes a toilet? Ad lastly, how to size pipe if you're using a manifold system(s)? Thanks alot Quinn!!

[@AWAjakeoliver9]

So helpful! I'm currently in trade school and this refresher was amazing! Could you do a video on sizing Waste and vent also? I always struggle with DWV more. Especially doing the Cross secionals. Thanks!

[@willplumb]

That's awesome to hear! Thanks for the thought on sizing waste and vent - we're planning a bunch of videos, so we'll keep this topic in mind. Best of luck in trade school. It's a great career.

[@drmyers56]

Great video. Nice drawings. Just the hot (red) on the right, cold (blue) on the left makes me itchy. 😉

[@willplumb]

Ahhh you're right! We spotted it too late. We just made a new drainage system video, and hopefully avoided any itchy mistakes. 😂

[@macrapidito1]

Great put together video. Easy to understand 😎😬

[@willplumb]

Thanks! Glad we could help.

[@jimlofaro5695]

great explanation and video. Bravo. great Teacher.

[@Doc_GME]

GME to the Moon! Nice job.

[@coreyaldridge1753]

What a very good video and presentation. Very informative and knowledgeable.

[@willplumb]

Thank you. I'm glad we could help!

[@jacksprat7087]

New house. 1700 sq ft, 1 story, 32” crawl space under floor, no basement,4 water fixture zones. I’m putting in a master manifold with 1” from street and 3/4” out to 4 sub-manifolds then 1/2” from them to each fixture. The master will have shutoff valves for each zone. Because of this no individual fixture will have a shutoff valve. There will be no lines in the attic nor the walls and no connections below the floor.

[@Gamblor2000]

This is such a great explanation. I found it very useful. Thank you!

[@Bran-to-the-doh]

This. Is. AWESOME. Thanks!

[@prestonmiller9552]

Excellent! Answered a lot of questions I have been wondering about.

[@flafichi]

WOW!!! Wonderful explanation. The best ever. Just subscribed. Thanks!

[@Z-add]

In gravity fed plumbing where you have a water tank on your roof. The distances will be from the tank and not the water meter. Plus will their be other differences

[@bryanhunter1927]

I feel a little bit smarter thank you

[@ADRIAN-gb5mi]

THANKS IM LEARNING A LOT FROM YOU.

[@joanmanuelist]

Your video is so perfect and well explained. Keep up the excellent work

[@readmore3634]

I almost always run a dedicated 1/2" hot water line to the kitchen sink. Hot water arrives in seconds instead of minutes. Saves heating costs and saves water. The wife will love you for it. Water travels much faster through 1/2". I almost always over size my cold system...it doesn't cost that much more and you can add fixtures later if you want. I almost always under size my hot water system....(slightly)....people use less hot water than cold. You save on heating costs and saves water.... and it gets there faster.

[@eddylee587]

Excellent demo! Great information! Thanks

[@AlexSherm]

Great timing going to install a filtration system for my well and was wondering of sizing the pex pipe after it. I'm just running 1inch through the system and will switch to 3/4 to feed the branches.

[@tcthetford]

Thank you for not Telling a lie!

[@Creeder991]

Another very helpful video. Thank you

[@willplumb]

Thanks! Happy to help.

[@michaelphillips7973]

great video but I had a question about the sizing connecting to the water heater. I ran through my calcs using the provided method and found the last stretch of pipe connecting to my water heater should be 1". Unfortunately I dont think they make water heaters with this inlet size. I know I can just step it down, but the whole point of all this is to not impede the flow rates or restrict the lines, right? I'm also planning on adding a hot water recirculating pump and a home water filter system as well.

[@chrisosti]

Great video! Very good approach, easy to understand!

[@willplumb]

Good! Thanks for watching.

[@camb565]

That was exactly what I needed! Thank you man!

[@danlewis4886]

Actually having dealt with both pex a and pex b I can honestly say that the decrease is mínimal even Viega has a video on that. Dan Lewis MA. Plumber since 2003

[@JimmyVern1]

Thank you for excellent education!

[@willplumb]

Of course! Thanks for watching, and I hope this helped your project!

[@jeffbostic1490]

Very informative. thank you.

[@viviangirard5075]

While this is some good book interpretation, I use much simpler rules. Since I care a good deal about the environment, using less water and particularly less hot water is a priority. I only use low flow fixtures (1.5 GPM max for all faucets and showers). That saves money too! I’ve done a good amount of DYI plumbing repairs and pipe replacement on my properties. In a typical household -up to 4-5 people- I rarely expect more than 2 fixtures to be used simultaneously, a ½ pipe is plenty for the entire house. It’s much better when it comes to hot water since a ¾ pipe holds a lot of water that ends up being wasted each time the hot water gets turned on. One can install a recirculating pump, but that’s more money, more trouble and still plenty of wasted energy. Five years ago, I tried a ¼ pex line (not a typo) on my bathroom that has a 90’ long water run from the water heater to the shower. I have about 60 PSI at the water meter. Even with that size pipe, the pressure at the shower head is sufficient so I just left it that way. Running such a small water line saves a good amount of plastic, wait time and more importantly a lot of hot water each time I turn on the hot water (a ¼” pipe reduce hot water waste by 75% vs a 1/2 “ pipe and 90% vs a ¾” pipe). It probably wouldn’t work as well if one was trying to fill up a bathtub regularly but there is no bathtub in this situation. Worse thing that can happen if you undersize your water pipes? On some rare occasions the water pressure may feel a little low. That’s hardly a life-threatening situation!

[@darylschnur5044]

I loved your video, I decided just to watch it out of curiosity. And ended up finding that a few of the runs in my house were actually undersized. But I am curious about fridge water dispenser and ice maker? What would the WSFU be for those? I couldn't even find it in the 2024 book.

[@matthewpullen9549]

Hey William! Fantastic video. Very informative. Not sure how quickly you’ll see this, but I have a half bath that I’m converting into a full bath. And also I’m adding a washer dryer on the opposite side of the wall that hosts the vanity. It’s slab on grade… What do I do in order to make sure everything is up to code? Specifically, 1) how would I vent the new washer (tie into vanity or separate? And which drain needs to be higher if they can join?) 2) Based on your video, if the supply line to the half bath is only 1/2” for the toilet and vanity, I will have to upgrade that supply line to 3/4”, correct? Since im adding 4 unit shower and “x”unit washer **To help clarify, water heater is about 10’ away vertically from 1/2 bath. Anything helps. Thanks man

[@sebperkins5654]

When you are working out the furthest appliance from the entry point, you don't mix the cold line with the hot lines. You do it from the cold line all the way to the furthest appliances cold feed.

[@saulcaravantes6438]

Great video ! Very helpful

[@Kingloki13]

Awesome video and very informative!

[@johanbronte]

Many thanks

[@curtiscox6469]

A lot of great info here. Thanks.

[@rougesunset]

Wish I could show you my pretty diagram, it's crazy how simple it is compared to actually looking at the mess of galvanized and copper pipes in my basement 😅

[@cindypajer2458]

Great video - The only thing that I was unclear on was how to determine the system/static pressure. How do I determine that?

[@AngelofOntario]

I’d like to learn how to hook up a whole house water filter system for this too & if that increases pipe sizing needs. Also, why does most whole house filter systems have 1” pipe inlet/outlets, but my pressure tank (well water) has a 3/4” outlet? Makes it confusing & I’m not sure which size to have for my Main Line! From this, I’m confident all my fixtures I can run 1/2” branches to & be fine, though!

[@davidcook5987]

You the best thaks for you info

[@willplumb]

No problem! Glad to help!

[@tsparks4110]

Great video! The illustrations are AWESOME!!! I’m about to repipe my whole house as it currently has about 4 different type of piping, it was built in the 50’s! This has come at a perfect time. I’m working off a .5hp sub pump sitting at about 60ft deep in a 75ft 4” well with 60psi and 10-11gpm. The main line from the pump into the house is 3/4” and about 15ft distance before reaching the 20gal diaphragm tank. In your example water begins at the meter, as I don’t have a meter, where do I begin sizing from? Would it be from the well head, or would it be from the diaphragm tank? The reason for my question is I’m at 15 wsfu for my cold (including 2 hose bibs =3.5wsfu).

[@onemomsdrm]

Great info! Very clearly explained...excited to map out my plumbing tomorrow!!

[@JohnThomas-30571]

My water line is 3/4" pex from the shutoff valve coming in from the street and runs to the tankless water heater (in the basement. Then it is 3/4 to each end of the house for the basement, main floor and then up to the 2nd floor. Each fixture is supplied via a "T" to 1/2" pex. When someone is in the shower and someone else flushes a toilet and/or turns on the kitchen sink the pressure in the shower drops significantly. Then if the washing machine get turned on, forget about the shower. I've never experienced this before. What can I do? Thanks, John T.

[@GeorgesCanadianVentures]

Excellent! 🇨🇦👊

[@scottfeatherstone7156]

Great video very informative thanks

[@willplumb]

Thank you, happy to help!

[@peterman8058]

Very informative! Thank you!

[@willplumb]

Glad you found this helpful!

[@Will7981]

I didn’t know plumbing required so much brain power. Lol

[@eyadnazer6936]

thank you for your explanation. but how to determine the size of the make cold water line that supplies the storage tank ?