Over 698,000 strictly plumbing related posts
Plumbing education, information, advice, help and suggestions are provided by some of the most experienced plumbers who wish to "give back" to society. Since 1996 we have been the best online (strictly) PLUMBING advice site. If you have questions about plumbing, toilets, sinks, faucets, drains, sewers, water filters, venting, water heating, showers, pumps, and other strictly PLUMBING related issues then you've come to the right place. Please refrain from asking or discussing legal questions, or pricing, or where to purchase products, or any business issues, or for contractor referrals, or any other questions or issues not specifically related to plumbing. Keep all posts positive and absolutely no advertising. Our site is completely free, without ads or pop-ups and we don't tract you. We absolutely do not sell your personal information. We are made possible by:
Author:
tjgbrew (NJ)
Hi All,
I’ve been reading the forum for a long time, but I’m a first time poster.
I’m getting set to replace the supply pipes in our home –the system is mostly the original galvanized steel from the 1920s and is terrible. I used a fixture count table (1.5 baths but plans to add another in the future) and easily concluded the house needs 1” copper. We have a ¾” supply from the street and the old pipes are 3/4” with some newer 1/2" copper lines to fixtures. I plan on running mostly copper with maybe some PEX up to the second floor bathroom.
BUT When I spoke with the local plumbing supply house they said most people in the area use ¾” instead of 1” because the water pressure is so high in our area. The pressure is high with a PRV (we have one) but I thought sizing was about volume and not pressure. Any thoughts on whether I can save a bundle of money in avoiding the 1” pipes? I just don’t want to lose hot water in the shower when the dishwasher is running, etc…
Thanks!
Tom
|
Post Reply
|
Author:
KCRoto (MO)
Based on your current size, you would be in the 3/4 range, and with an extra bathroom, if you follow the chart, would be 1". Now, what you need to consider is that the chart is designed for a pressure range of 40-60 psi, and that takes into account that every fixture is running wide open. Realistically, you won't have every shower, toilet, lavatory faucet, kitchen sink, dishwasher, and hose bibb all running at the same time. A more realistic scenario is having 2 showers, the laundry, and dishwasher running all at once. 3/4" should be plenty large to supply your needs. My pressure is about 74 psi and I don't lose pressure with a shower, bathtub, laundry, and dishwasher all running. Your concern about running out of hot water is an entirely separate issue.
Now, while you have the walls open, you can run 3/4 hot and cold everywhere in the house, and go ahead and put a return line in for a recirculation system in, and insulate the hot water lines. If you wanted to add a second hot water tank at the same time, it might be prudent depending on your needs, or if the new bathroom is going to be a car wash.
|
Post Reply
|
Author:
m & m (MD)
You could limit the 1" to the main trunk up to the first branch and downsize from there but with todays' fixture flow rates, I think you'll be fine with 3/4".
|
Post Reply
|
Author:
hj (AZ)
You have no where near the demand that would need a 1" line, unless you also have a large irrigation system for your yard.
|
Post Reply
|
Author:
packy (MA)
1 inch is standard around here. if 3/4 is all they need then the reduction is made inside the house.
|
Post Reply
|
Author:
hj (AZ)
3/4" is the smallest we use, but it is "standard" if that is all they need. We do not "screw" them by charging for a larger pipe than they need, then reducing it in the basement.
Edited 1 times.
|
Post Reply
|
Author:
tjgbrew (NJ)
Thanks for the advice. It is quite confusing to say the least.
Just to be clear on the house – it is 1.5 baths, kitchen sink, dishwasher, clothes washer, utility sink and hose bib (no irrigation!), with plans to add another bathroom up on the third floor eventually. The difference in cost for 1” fittings is pretty surprising but I’m happy to pay it to avoid the risk of another bad system.
I’m thinking of running PEX to the second floor bathroom, probably four ½” lines that will be about 20’ long. One hot line to tub and one to sink – the cold shower line will share with the toilet.
Is this plausible with the ¾” copper lines or should I just go with increasing to the 1” on the main hot and cold water lines in the basements?
Again, thanks for the help!
|
Post Reply
|
Author:
packy (MA)
i like to mount 1 inch copper manifolds in the basement with 1/2 inch pex mini ball valves for each branch.
if you are going to run pex to the new bath, run 2 hot and 3 cold. 20 feet extra of pex will not cost much.
you can get the manifolds that have 3/4 pex crimp inlet and the other end is spun closed to make life easier.
|
Post Reply
|
Author:
hj (AZ)
I, and most other plumbers around here, would ONLY use 3/4" for a house with your water needs. The ONLY way you would need a 1" line is if you had a house full of people who were turning on EVERY faucet at the same time, and even then you might not notice a drop off with a 3/4" line.
|
Post Reply
|
Author:
tjgbrew (NJ)
Cool – Thanks for the help. The consensus seems to be that ¾” will work but 1” won’t hurt. I’m thinking if it isn’t necessary, then I’ll go with the smaller size. I don’t plan on installing a hot tub any time soon.
Packy – just to be clear, I’m thinking of putting in PEX to the second floor bathroom now, but plan to add another bathroom up on the third floor eventually, so that will be 2.5 bathrooms in the end. Will it be an issue to split a ½” PEX line between the shower and toilet? It would tap into the ¾” line in the basement. I have a tight squeeze through the wall so I was trying to cut the number of lines. Because it is only four lines, I wasn’t going to use a manifold - just tees off the main lines.
Edited 1 times.
|
Post Reply
|
Author:
packy (MA)
if you are going to split the lines, split the toilet and the lav. run a dedicated 1/2 inch to the shower.
|
Post Reply
|
Author:
tjgbrew (NJ)
Hmmm - ok. Thanks for the advice.
So are the fixture count charts used by anyone? Because according to them it seems like only the smallest house with one bathroom should be using 3/4" pipe. Obviously it doesn't sound like people here worry about it too much?
|
Post Reply
|
Author:
hj (AZ)
quote; So are the fixture count charts used by anyone?
I used them 60 years ago while I was in apprentice school but haven't even seen one since.
|
Post Reply
|
Author:
packy (MA)
that is why we run 1 inch copper into the house..
|
Post Reply
|
Author:
hj (AZ)
If you are not sure, why not just use 1 1/4" then?
|
Post Reply
|
Author:
packy (MA)
1 1/4 inch is big enough for Pablo Sandoval to use for a bat.
|
Post Reply
|
Author:
tjgbrew (NJ)
Is that sarcasm? The decision was between (still) conflicting advice over 3/4" or 1".
It doesn't sound like you guys will ever agree on that one. I know the cost difference isn't small but is there any downside to oversizing?
|
Post Reply
|
Author:
hj (AZ)
no, it is done all the time when the pipe goes a long distance.
|
Post Reply
|
Author:
KCRoto (MO)
3/4 will provide more than adequate flow for your needs. If you were running a hotel where all the fixtures might be in use at the same time, I would use 1". If you are still unsure, run the line in 1" and just spend the extra money.
|
Post Reply
|
Author:
tjgbrew (NJ)
I saw an earlier debate in this forum about pipe increases.
The conclusion was that increasing pipe size to a size bigger than the main street line won't do anything. Is that true? The fixture unit charts definitely says to do that.
But if volume constrained by the 3/4" line from the street any advice to increase to 1" seems misguided. What am I missing?
|
Post Reply
|
Author:
KCRoto (MO)
Larger pipe sizes have less resistance to flow and therefore create less turbulence inside the pipe. This amounts to less erosion and less noise, and does have some small benefit with pressure drops, but if your pressure is high anyway, you probably won't notice.
|
Post Reply
|
Author:
tjgbrew (NJ)
It seems like the argument for bigger pipes is around volume - but if the bottleneck prevents a volume benefit, then I don't understand the practice or recommendation. I'm obviously missing something.
|
Post Reply
|
Author:
hj (AZ)
IF it is a very long pipe, then water flow through it will generate a friction loss commensurate with the flow's velocity. Therefore, a long larger pipe will lose less dynamic pressure under high flow volumes.
|
Post Reply
|
Author:
tjgbrew (NJ)
Ok. So all my main cold lines that I would boost to 1" in my basement total maybe 40'. That doesn't seem like a "very long pipe".
|
Post Reply
|
Author:
KCRoto (MO)
It really isn't, which is why I would stay with 3/4"
|
Post Reply
|
Author:
hj (AZ)
And it would also probably NOT be a "high volume flow" either.
|
Post Reply
|
Author:
bernabeu (SC)
IMO:
Run 1" into the house to cover ANY future needs.
Once INSIDE the crawl space or basement or other ACCESSIBLE area THEN reduce to 3/4" using a 1x3/4x3/4 Tee with the unused 3/4 'stubbed' and capped. (for a future)
ps. tees are 'called' run-run-bull (bull=side outlet)
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
|
Post Reply
|
Please note:
- Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
- Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
- Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
- Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.
Search for plumbing parts on our sponsor's site:
Special thanks to our sponsor:
|