Need critique on residential plumbing layout

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Rossn, Apr 4, 2021.

  1. Jeff H Young

    Jeff H Young In the Trades

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    are you repiping do to poor volume of water? I looked at original post no mention . why all the testing and gauges? just size your pipe according to code would be my advice the 275 foot long water service is too small obviously but that doesn't mean you need to replace it now. you are repiping the house so pipe accordingly and you aren't required to run as small as code allows you can go bigger but it can be waste to go much oversize
     
  2. Rossn

    Rossn Member

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    Hi Jeff, very good question and point well made.

    I'm re-piping due to a deep remodel (pretty much a rebuild) of an original 1960's home; however with the remodel there are a lot of core plumbing changes occurring, which requires me to confirm I will have sufficient pressure@flow. I didn't have any concerns about the supply until I saw the test results from the test a few years back - the pressure drop seemed to be very premature (68psi static, 40 psi@10 GPM, 22 psi@12.5 GPM). I fully agree and will need to size the house appropriately, and if I really find there are issues on the supply side, will have to do an upgrade or work around those at that time. However, knowing if there is going to be a supply issue may help me make some decisions that might otherwise fall one way or the other. Would prefer to put off any water main-supply line change at least a few years, if possible, and still have the new bath usable.

    Here are the plumbing changes from the original, noting that usage patterns will also change with an in-law suite added (90% of the plumbing replaced)
    • Added 3/4 bathroom at 125 from supply entrance (prior furthest fixture at about 80', 9' lower.)
    • Added 2nd washer at 150' (forgot about this being the furthest fixture)
    • Added 2nd kitchen sink
    • Relocated 3/4' bathroom to about 85'
    • Added garage 'laundry sink', about 100'
    • Added D'Mand recirculation for these far fixtures with dedicated recirc line.
    • Added 2 hose bibs @ 95'
    • Added prep sink
    • Added pot filler
    • Moved kitchen sink/dishwasher
    • Added second sink to bath
    • Added second shower head to master bath
    • Added Comfort PM Auto recirc with dedicated line.
    • Adding water filtration (but not looking like whole-house is an option, given pressure drop)
    • Was going to add a PRV, due to seeing some pressures spike to 100psi over-night a few years back, but thinking I will need to ditch (or oversize) that, seeing the pressure drop at volume issue.
    So, I am approaching planning this more like a new build (but with 'remodel limitations').

    I would also add that I haven't much used 2 of the baths since being here (due to being largely unusable due to wait times, cold, backups, etc; now gutted), so I don't have a sense if there were concurrency water pressure@volume issues pre-existing.

    Thanks for chiming in.
     
    Last edited: Apr 7, 2021
  3. Jeff H Young

    Jeff H Young In the Trades

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    seems the biggest limitation is the 1 inch service . I've had some difficulty following your blue print kinda small for me so all the details are not clear. hot water circ a must in my opinion . a major place that might be a problem is large bath tubs can fill slow. 1 inch lines somewhat near the 150 foot run to washing machines to a bathroom nearby then run 3/4 to 5 foot away or as close as you want .
    4800 is a big house , which to me implies a large investment , bigger house bigger investment , I'd say you don't want to scrimp on size of pipe , quality of material or workmanship. of course going way oversize doesn't gain you much either. I'm not being real specific but trying to convey some ideas.
    I'd be coming in house with 1-1/4" or 1-1/2" . and the service to house in future I'd run 1-1/2" I don't think 2 inch be needed but you're not doing that now. upping meter size is a consideration as well but again not dealing with that now
     
  4. Terry

    Terry Administrator Staff Member

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  5. Rossn

    Rossn Member

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    Thanks Jeff, Wayne, Terry, and James - I appreciate all the help working through this! I really need to do something for you guys when I get through this.

    It does sound like the service is the issue, and I'll have to treat it individually. the house is large, which is why I will rent out part of it. Some houses may have a lot of users; in this case usage would be 4 people + 1 renter in the furthest end. Point being, I'm not likely to have have 4 showers running concurrently with a line outside the door.

    The overall project is also big... I'm rebuilding about 50% of the house, and doing about half the work myself, including things like design and install of the radiant heat system, electrical, etc. A bit too much with a 55hr a week job and family, but have to keep shoveling! Multi-year construction living, not much sleep.

    I've had most of the L copper for over a year now, so the main house will be copper, and I am using viega propress. Far-end and radiant with Uponor ProPex. Agreed on sizing, quality materials and getting it right with good design and workmanship.

    To clarify... when you say coming in house with 1-1/4 or 1-1/2, you are saying 1-1/4+ on the interior of the home, to the mechanical room (where it branches)?

    If so, that would match with what I was tallying up as WSFU's.

    For overall house, using the guidelines from 2015 IPC, I get:

    Using 'Bathroom Groups' (supplemented for additional Lav's, etc)
    Hot/Cold/Combined WSFU's
    28/16/36


    Alternate approach of tallying all fixtures individually would be:
    35/18/41

    Sec 201 doesn't reference using E103.3(3) to then find GPM, but it the only way I see to get to GPM. If I use that, it says 36 WSFUs = 25 GPM for the main distribution pipe (hope I am using that term right) in the house. Assuming max copper velocity of 7 ft/s (cold), that would give 18GPM for 1" type L or 26.6 GPM for 1-1/4" type L... so IPC sizing would be for 1-1/4" on the main distribution pipe leading to the mechanical room. Which matches what Jeff suggested.

    Does this sound right and typical for a 4-1/2 bath home with a few extras (2nd washing machine, etc)?

    Terry, thanks. I had been studying your page on that earlier. Something funny is up here, in that 1 WSFU doesn't appear to be universal. In your version, things like water closets, showers, washing machines are dramatically different WSFU's:

    2015 IPC:
    upload_2021-4-7_12-40-30.png
    upload_2021-4-7_12-41-24.png
    upload_2021-4-7_12-42-2.png

    And the water supply line sizing table seems to use different units, too (so it is not just about low-flow fixtures).
    50 - 60 psi, 3/4 meter, 1" Distribution Pipe, 400' = 9.5 fixture units, not the 17 that your chart shows.

    Maybe yours is a different standard, such as UPC, or maybe they changed the definition of a WSFU between the time you took your table, and the 2015 IPC?
     
    Last edited: Apr 7, 2021
  6. Rossn

    Rossn Member

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    For some reason, the site dramatically downsizes all images, and have a very low size limit on uploaded images as well. I posted a larger one here (downloading it shows larger). Upstairs fixtures are red, downstairs fixtures are pink.

    Reason for not tapping directly into the main distribution line for west end cold supply is because I also have a well (pump needing replacement) that I would like to be able to manually cutover for supply, if needed. I didn't show the east end of the house yet, given the west end is the near term priority, but can provide if needed.
     
  7. James Henry

    James Henry In the Trades

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    When you tally up WSFU for the service pipe coming out of the meter to the entrance to the house you use .75 of the WSFU on fixtures that use hot and cold water. When you size individual branches you use 100% of the hot or cold line WSFU running to the fixture.
    I took your total WSFU and applied them to the graph. It sounds like your trying to make caviar out of fish sticks here. Good luck.
     

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  8. Rossn

    Rossn Member

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    Thanks for the education... I had not been digging into the charts yet, but assuming the needed flow is available, as if there is a supply line sizing issue, that would have to be handled independently of the remodel.

    Are you suggesting that it would be silly to run a 1-1/4" as the main distribution pipe (given the bottleneck on supply) and that I should size based on available supply (not calculated demand), or are you saying that I need to first upgrade the supply between the meter and house?

    If I add up all the things I can think might run simultaneously in the house (3 showers, 1 laundry, 1 toilet, 1 dishwasher, 1 lav... but does not account for a hose or irrigation running), I get 15GPM for the main distribution line, which is much less than the code calculation gives. However, it sounds like I am supposed to size according to code, not any limitations I have.
     
  9. James Henry

    James Henry In the Trades

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    Because you house is so far from the meter your kinda in a bind, I feel sorry for ya. Your trying to do this backwards, the building plumbing is always calculated first and that determines the water meter and water service line size. The distribution pipe in the building should never need to be larger than the service pipe. When you size the piping in the building you start at the highest and furthest fixture in the building and work your way towards the service pipe adding up the WSFU,s as you go and comparing the amounts to the WSFU, pipe size charts increasing the pipe as required by the amount of WSFU,s on it.
    If I were in your situation I would size the pipe in the building as normally required and plan on installing a booster pump if needed and eventually run the correct size service line in pex. You can get some info on booster pumps on here on the PUMP forum.
    I seriously think that trying to run larger pipe in the house to try to solve the problem is the wrong way to go.
     
  10. Reach4

    Reach4 Well-Known Member

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    I have not followed the whole thread, but to decide where your pressures drops occur, you want to get one or more pressure gauges. If you put a garden hose thread pressure gauge on an outside hose spigot, the indicated pressure will be that where the tee is that splits off to that spigot. Such a gauge is usually under $20, and often a lot under. A pipe not flowing water does not have a pressure drop.

    You can also attach such a gauge to a laundry spigot or the drain for the water heater. So by checking the gauges, you can tell what the pressure is at the street when the house does not use water. You can see the drop at various points.

    If you are running new plastic pipe from the street, it is OK to go bigger than you need. The price of the pipe is a small part of the project.
     
  11. Rossn

    Rossn Member

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    James - I hear you about the typical order. However, I also didn't think anything was being oversized to compensate - that was not intended. Can you elaborate on those concerns? Also, other than being bad practice/convention, are there technical issues with sizing inside to the 'right size', if that turns out to be larger than the supply (knowing it may later be replaced)?

    To be honest, we may get everything put together to find 10gpm is practically fine... or not, but that could dealt with directly or with workarounds as you have suggested, then.

    Reach - yeah, that will happen... some time frees up tonight. The thing I have to focus on first is putting the house back together (I'm not going to have immediate issues), and then if there is a practical supply issue, I'll have to work through it. For me, new supply line means directional drilling.
     
  12. James Henry

    James Henry In the Trades

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    I was under the impression that you were thinking about increasing the size of the distribution lines, my mistake. Size all your inside pipe appropriately, if it turns out that their bigger than than the service line, that's fine, you don't want to undersize the pipes buried in the wall and you may eventually install the correct size main.
     
  13. Rossn

    Rossn Member

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    No worries. I was not suggesting that. Other than the fact it is a bit backwards to look at the main distribution first, am I following the calculation correctly that at 36 Combined WSFU's (based on 2015 IPC), that expected flow is 25 GPM, which would require 1-1/4? Just making sure that using 'Table E103.3(3) Table for Estimating Demand" to convert from WSFU's to GPM is correct, given Section 201 doesn't mention that. If not, how do I get from WSFU's to GPM (or ultimately copper Type L size)?
     
  14. James Henry

    James Henry In the Trades

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    At 6ft./sec. you are correct. E103.3(3) for WSFU to GPM.
     
  15. Jeff H Young

    Jeff H Young In the Trades

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    1 1/4 minimum to mechanical room I havent actualy sized it but am positive 1 inch would be small. I agree to size it apropriatly but if your one fixture unit under needing to go to next size up it wont hurt to go bigger. not recomending going bigger based on undersized service. with such a long run rounding up on pipe size when its very close might not be a bad thing
     
  16. Rossn

    Rossn Member

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    Thanks James and Jeff. You've been awesome.

    Unfortunately, I was thinking stepping up from 3/4" to 1" main distribution was going to be plenty good and already ordered valves, moen flo, etc, but much better to catch and correct this early. I will get 1-1/4" parts ordered, as I have everything else.

    The only bummer about going this size is how long it will take to get a truly cold drink of water!

    Jeff - I'm at 36 WSFU's. 1-1/4" Type L should have 41 WSFU's@7fps and 53 WSFU's@8fps. If I didn't goof up (which I wouldn't know), it seems I should have a good amount of head room without needing to bump up.

    I'll break down the rest of the branches by fixture units and see where I fall, using E103.3(3) for WSFU to GPM.

    A few summers back, when I randomly checked water pressure during irrigation season, I was seeing pressures go to around 100psi, but only at night. It was odd. Talked to the water utility this week, and they thought that was out of character (and he was thinking I was actually pretty high for this area at 63 psi at the house).

    Based on the history, I had been planning on a PRV, but after talking to him it does not sound expected. PRVs seem to have a healthy minimum pressure drop (and with flow I may be at low pressure until I replace that line), IPC says plan on 20% reduction in calculations, and they seem to have a limited life.

    Should I drop the idea of a PRV?
     
  17. Jeff H Young

    Jeff H Young In the Trades

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    ok then 1 1/4 sounds fine. the pressure going higher at night is typical less demand . if you did need a prv it would be close to the house likley your mechanical room. Actualy I think you shouldnt be too bad with the 1 inch of cource it could have a kink or rock lodged someplace.
    monitor pressure again 100 psi too high
     
  18. Rossn

    Rossn Member

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    Thank you. I have a gauge on it tonight to see if it shows anything. interesting is that the utility mentioned that most of the pressure in my area is generated by head from the 4M gallon storage tank. I'm down a hill from it. He even mentioned trying to recall a maintenance event that could have caused the pressure to spike.

    Another interesting fact in this whole volume/pressure drop situation is that whether the lawn irrigation (near the house) kicks on or a battery timer activated yard hydrant valve turns on 12psi regulated drip tape in the (large) garden (keep in mind, 150+' away from the house), I hear the rushing sound of water through the water line, in the house (no drywall). I'm not sure if that might indicate an obstruction upstream of the yard hydrant. Pressure checks tomorrow.
     
  19. Rossn

    Rossn Member

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    This is where the irrigation ties into the 1" copper line. I'm assuming no one sees an issue with this tee that would lead to the pressure drop. Also saw some small dents in the pipe when I had it dug out, but that was just a 5' section.

    irrigation_to_supply_sm.jpg
     
  20. Reach4

    Reach4 Well-Known Member

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    Just because you run 1-1/4 pipe for the long distance, that doesn't mean that you cannot use 1 inch valves. Pressure drops add, rather than being controlled by the smallest piping, within reason.

    But then your nominal 1 inch valves may not be full port valves.

    Your need for a PRV will be determined by what pressure the water company/city provides. PRVs can be a significant restriction, and sometimes you make them larger than the pipe.
     
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