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PEXvs copperflowrate chart

Those figures are not what someone heard might be the code someplace, I referenced the ASTM numbers. That testing you qestion is done by the the "American Society of Testing & Materials" they are saying that is what the pipe is rated for to meet that standard. They are not saying you can't get more water out of the pipe under certian conditions only that is what it is rated for, to meet the plumbing code. Contact ASTM with further questions Im sure they can explain better then I.

No, again the maximum Water Supply Fixture Units are based on ASTM standards. If you use the home run method or a variation which is o.k., you still can't exceed the WSFU's as well as the header has to be sized in accordance with ASTM standards. Im taking this time to explain this to you because; I know you are not a licensed plumber and you have a open mind.

Water flow electrical pressure switch pex to pexinstructions

Thanks. I dont understand WSFUs, I deal in gpm in both water treatment and well pumps etc.. So if you will, how do FU counts differ from adding up the gpm needed by the fixtures in a private residence? And all the charts I look at says plastic pipe has a friction loss less than copper or steel pipe of the same size and I believe PEX is as smooth as other plastics. So why would homerun PEX have to be increased to the next larger size? Gary Quality Water Associates

You do not need to use the manifolds--I am not crazy about the plastic premanufacturered ones since I have had two that leaked. If I manifold a system, I make my own manifold, but there is no rule that Pex must be manifolded. It can be run and teed like any other water piping material. On a standard 2 bath, I generally start out with 1", use a 1 x 1 x 3/4 tee to go to the WH, then a 1 x 3/4 x 3/4, with each 3/4 serving half of the house. I run 3/4 with 1/2 brances to the fixtures, up to the last 2 fixtures then branch with 1/2 to each. Pressure balance valves have made pressure flucuations safer and low water consumption fixtures have lowered the water demand. Deb The Pipewench

How much testing is actually done to come up with those figures? BTW, I hear code in WA or OR says if the house has more than 3 bathrooms, the service line must be 1.25". Anyoe know if that's true? I question if both of those requirements are due to actual flow tests; especially if the PEX system is using a manifold and not plumbed as copper is with fittings everywhere. Does anyone know for sure? Gary Quality Water Associates

Water flow electrical pressure switch pex to pexinstallation

Are those figures based on home run or with the use of fittings as copper would be plumbed. Gary Quality Water Associates

3/4pexvs copperflowrate

Water flow electrical pressure switch pex to pexmanual

You don't have less pressure you have less volume, here are some numbers off the water sizing charts. ASTM F876 & F877 Maximum Allowable Load for 3/4" Pex Pipe is 11 WSFU ASTM B88 Type M Copper Max. Load is 18 WSFU Pex 1/2" Max. is 4 Copper 1/2" 7.5 WSFU What this means is you can have 4 full bathrooms with 3/4" copper and some left over to supply other fixtures. However; with 3/4" pex only 2 full bathrooms and some left over for other fixtures.

hj said what I was going to say! Another thing you can do is use a pipe and fitting system that has full port fittings instaed of crimp ring style. Rehau and Wirsbo use these full port fittings. Better joints, larger inside diameters, but expensive tools.

The manufacturers like the manifolds because they can sell you the manifold and more PEX tubing. It also minimizes the pressure/volume loss caused by multiple inserted fittings.

With the new pex pipe with crimp on fittings. Would you have less pressure. 3/4 pex vs copper. With the 3/4 pex the fitting lowers the size to about 1/2" am I misiing something? Also do you have to use the manifolds? Thanks

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Smaller tube size restricts FLOW, so that at a given device with a given flow, your dynamic pressure will be lower. It seems advisable to upsize the PEX. Search this and other forums for info on PEX manifolds. I recall there have been some issues, but manufacturers recommend them.