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Old 12-18-2012, 09:05 AM   #16
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Supply Line Sizing with PEX


I think for this I'd prefer to have the hot go to a PEX manifold then run 1/2" lines to each room. You'll have the least amount of water to displace to get hot water and none of the complexity of having recirc loops/pumps. Our first floor bath takes maybe 20 seconds to get hot water and the kitchen is the same. The upstairs bath still has about 1/2 of the run in 3/4" copper and takes a good 90 seconds to get hot water, but I haven't remodeled it yet---I expect it will take ~40 seconds when complete based on distance.

3/4" pipe has over double the volume of 1/2" pipe.

Both our previous and current houses are like this and have no issues with flow or pressure loss. Our current house's first floor has a fairly high flow shower head in the ceiling and we have no problems taking a shower and flushing the toilet at the same time, not even a hint of a pressure change.

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Old 12-18-2012, 10:03 AM   #17
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Supply Line Sizing with PEX


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Originally Posted by tylernt View Post
Alternatively, you can get a pump with no thermostat and no timer, just a button. When you enter the bathroom, you push the button. About a minute later, you have hot water. This saves more energy and while pipe insulation here still helps, it's not as critical since you're not recirculating very often.

In either case, you waste less water. This could be important if you are in a drought area or on a private well that tends to go dry (like mine).
We have been looking at the D'mand system by Wirsbo/Uponor that works with a push button. Everything is accessbile right now so everything will be insulated while we have the chance.
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Old 12-18-2012, 10:11 AM   #18
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Supply Line Sizing with PEX


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I have the cold trunk on 1", not sure it needs to be that big.
The WSFU calculation will tell you exactly how big it needs to be.

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Maybe hot water needs to be 1" as well? Or should 3/4" work for all?
Depends on what the WSFU calculation tells you.

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I had mentioned the 1" cold trunk to the plumbing inspector and he thought I might have pressure issues,
Yeah, might need to be 1 1/4" or 1 1/2". Bigger pipe = more pressure. The calculation will say for sure.

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he also thought the extra head to the 3rd floor might be better off separated to a different line than the 2nd and 1st floors, I think he said it would cause an excessive pressure drop to the to the other fixtures.
Could be, I have no experience with multistory dwellings.

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This is the first time I'm dealing with the large number of fixtures or anything more than 2 floors but mainly I'm trying to avoid what I've had in other homes we've lived in where multiple fixtures affect each other temperature (i.e. scalding or freezing when someone turns another fixture in the house on) or large pressure differences when another fixture is turned on.
Yep, fortunately, someone else has already done the empirical testing and come up with a formula to ensure that pressure drops and differences are within a small tolerance. They did all the hard work so all you have to do is plug in your fixtures and pipe length and out pops a number that will make you happy with your plumbing system.

Here's those links again:

http://www.engineeringtoolbox.com/Wa...ts-d_1073.html

http://www.engineeringtoolbox.com/wf...es-d_1075.html
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Old 12-18-2012, 11:46 AM   #19
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Supply Line Sizing with PEX


Tylernt -
So if I plug in all the tubs, toilet, sinks, showerheads, etc. I come up with 47 WSFU. Its approx. 120 ft to the 3rd floor fixtures. Based on that table it says I need 1 x 1 1/4, but talks about meters and street. The line from the well to the pressure tank is 1". The line from the tank to water treatment is 1" and the outlet of the water treatment is 1". So where would I step up to 1 1/4"? Stepping up the size will reduce my pressure won't it?

The other thing is that I don't see any accounting for pressure drop due to vertical head. I saw somewhere on line of just under 1/2 psi per foot so at my almost 40 ft to 3rd floor I'm looking at almost 20 PSI drop there I think.
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Old 12-18-2012, 11:49 AM   #20
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Supply Line Sizing with PEX


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Originally Posted by SuperJETT View Post
I think for this I'd prefer to have the hot go to a PEX manifold then run 1/2" lines to each room. You'll have the least amount of water to displace to get hot water and none of the complexity of having recirc loops/pumps. Our first floor bath takes maybe 20 seconds to get hot water and the kitchen is the same. The upstairs bath still has about 1/2 of the run in 3/4" copper and takes a good 90 seconds to get hot water, but I haven't remodeled it yet---I expect it will take ~40 seconds when complete based on distance.

3/4" pipe has over double the volume of 1/2" pipe.

Both our previous and current houses are like this and have no issues with flow or pressure loss. Our current house's first floor has a fairly high flow shower head in the ceiling and we have no problems taking a shower and flushing the toilet at the same time, not even a hint of a pressure change.
What did you do for cold?
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Old 12-18-2012, 11:51 AM   #21
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Supply Line Sizing with PEX


To add to what tylernt said-
You need to deduct 1/2 psi for every foot of rise in the piping- if I remember right its actually .433psi.
You also need to use the lowest pressure reading to the house- which would be 40 psi at your 40/60 switch.
So, you have 40 psi - (35' rise x.5)= 22.5 psi delivered to the 3rd floor.
Now you can begin sizing your supply and branch piping using the previous referenced site or your code book
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Old 12-18-2012, 12:04 PM   #22
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Supply Line Sizing with PEX


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Originally Posted by Rich View Post
What did you do for cold?
3/4" for the main trunk with 1/2" branches to rooms. In our first floor bath, it's fed by a single 1/2" pex line and we have no pressure fluctuations at all from flushes/sink/etc. Our old house had the same results in the second floor bath.

In my experience, pex flows much better than copper/cpvc as long as you minimize the use of fittings which is easy to do.

Our house had all the copper stolen from the basement while we had it under contract (short sale, took 3 months to close) so I ran all new pex. Since it's an unfinished basement and not really suitable for living space, I was able to lay it out for best flow/pressure including the placement of our new tankless water heater.
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Old 12-18-2012, 12:07 PM   #23
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Based on that table it says I need 1 x 1 1/4, but talks about meters and street. The line from the well to the pressure tank is 1". The line from the tank to water treatment is 1" and the outlet of the water treatment is 1". So where would I step up to 1 1/4"?
Yep I ran into a similar situation on my install. I have 3/4" coming in from my well, and the house was piped with 3/4" previously. This was probably code when the house was built, but codes have changed since then. So, I transitioned from 3/4" to bigger pipe where it was most convenient to do so, and used the big pipe from then on.

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Stepping up the size will reduce my pressure won't it?
It may seem counter-intuitive, but just the opposite. Stepping up in size will decrease the "fluid friction" or resistance to flow. This, in turn, will increase the GPM the pipe will deliver. So your 1" well, feeding 1 1/4" distribution, will result in MORE flow at the end of the run than if you ran 1" all the way. A full run of 1" pipe would be more restrictive and will choke down the GPM you get at the distant fixtures.

Case in point: My 3/4" well is feeding a 1" cold distribution (my house is tiny compared to yours ). But my water heater and hot distribution is 3/4". When I turn on a tub faucet and twist it to cold, I get more flow than if I twist the knob to hot. So, my 1" pipe coming off a 3/4" well will deliver more cold water than my 3/4" hot pipe will. So yes, stepping up in size from a smaller to a bigger pipe will increase flow rates. Admittedly, the 1" supply will impose an upper limit on the GPM you will get, but chances are your well can't supply that many GPM anyway.

You should forget about pressure, and think about GPM (Gallons Per Minute). GPM is a better indicator of piping quality.

Note, and TheEPlumber can confirm or deny this, but I don't think you have to run 1 1/4" for the whole house. After you have supplied several fixtures with 1 1/4 such that the remaining fixtures downstream only total 30WSFU, you can step down to 1". And as you go further and have only 14WSFU left to supply the last few fixtures, you can go down to 3/4". Could save you some money.

EDIT: I just read TheEPlumber's post about pressure loss in vertical runs. That really hurts your installation, so you might need 1 1/4" the whole darn way after all.
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Last edited by tylernt; 12-18-2012 at 12:20 PM.
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Old 12-19-2012, 12:15 AM   #24
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Supply Line Sizing with PEX


Quote:
Originally Posted by TheEplumber View Post
To add to what tylernt said-
You need to deduct 1/2 psi for every foot of rise in the piping- if I remember right its actually .433psi.
You also need to use the lowest pressure reading to the house- which would be 40 psi at your 40/60 switch.
So, you have 40 psi - (35' rise x.5)= 22.5 psi delivered to the 3rd floor.
Now you can begin sizing your supply and branch piping using the previous referenced site or your code book
So the problem with this is that the table only goes down to 30 psi. Do I need to raise the pressure out of the tank?

Last edited by Rich; 12-19-2012 at 12:17 AM.
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Old 12-19-2012, 12:38 AM   #25
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Supply Line Sizing with PEX


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Originally Posted by tylernt View Post
Yep I ran into a similar situation on my install. I have 3/4" coming in from my well, and the house was piped with 3/4" previously. This was probably code when the house was built, but codes have changed since then. So, I transitioned from 3/4" to bigger pipe where it was most convenient to do so, and used the big pipe from then on.

It may seem counter-intuitive, but just the opposite. Stepping up in size will decrease the "fluid friction" or resistance to flow. This, in turn, will increase the GPM the pipe will deliver. So your 1" well, feeding 1 1/4" distribution, will result in MORE flow at the end of the run than if you ran 1" all the way. A full run of 1" pipe would be more restrictive and will choke down the GPM you get at the distant fixtures.
Took another look at my pipes and the line from the well is actuallly 1 1/4 or 1 1/2" black plastic (PE I think?). It changes to 1" CPVC just inside the wall then runs about 2 ft to the pressure tank. The tank has a 1 1/4" inlet/outlet that is stepped down to 1" on each side. There is 1" CPVC run about 5 ft to a filter where it is stepped down to 3/4". The outlet of the filter is also 3/4" and is stepped back to 1" and runs about 18" to the softner. The softner has reducing bushings on both the in and out, so that I think I could step up on either or both sides of it as well. Does it make sense to step up after the softner the way it is now or does it make sense to bump up the rest of the piping as well?

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Originally Posted by tylernt View Post
but chances are your well can't supply that many GPM anyway.
I think I need to go through the steps of calculating the GPM both before and after the softner/filter to aid in figuring this out as well.

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Originally Posted by tylernt View Post
Note, and TheEPlumber can confirm or deny this, but I don't think you have to run 1 1/4" for the whole house. After you have supplied several fixtures with 1 1/4 such that the remaining fixtures downstream only total 30WSFU, you can step down to 1". And as you go further and have only 14WSFU left to supply the last few fixtures, you can go down to 3/4". Could save you some money.

EDIT: I just read TheEPlumber's post about pressure loss in vertical runs. That really hurts your installation, so you might need 1 1/4" the whole darn way after all.
Was looking at the IRC and found that they are using WSFU numbers quite a bit lower than the UPC in the charts provided before. In the IRC the combination WSFU comes out to 22 for 4 1/2 bath groups, a laundry and kitchen group. The method of calculation does discuss working the table backward to step down the sizes for each of the cold and hot water distribution lines. Still have the issue of my pressure being lower than the tables so not sure what to do about that yet.
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Old 12-19-2012, 12:55 AM   #26
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There is 1" CPVC run about 5 ft to a filter where it is stepped down to 3/4".

Does it make sense to step up after the softner the way it is now or does it make sense to bump up the rest of the piping as well?
Hm, I don't like that 3/4" in there. If nothing else, I would bump that up to 1". The others, I suppose you could wait and decide to upgrade them later if flow rates suck.

Quote:
Was looking at the IRC and found that they are using WSFU numbers quite a bit lower than the UPC in the charts provided before. In the IRC the combination WSFU comes out to 22
Well that's a bright spot. Do you know which your jurisdiction goes by? Different localities adopt different code standards. You might ask the inspector who will be signing off on your permit... he may just let you use the 30PSI table and call it good.

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