In2toys
Well-known member
the place we are in has 3/4 copper to everything. the tub fills FAST. Ditto on the pex crimper.
Re piping a house in pex
- Thread starter 86k10
- Start date
Beemer533
Well-known member
Is this what you are recommending in this pic? ....
Yes, you would run the 3/4" into a manifold and 1/2" to each fixture from the manifold...
mires
Well-known member
Is this what you are recommending in this pic? Or are you recommending 3/4 just to the first tee at the sink and 1/2 the rest of the way?
Either way would be just fine honestly but I would just take 3/4'' to the first Tee at the sink like you said and then carry on with 1/2''.
volleyball
Well-known member
I'd run 3/4 to the toilet if there is more than 1 person in the house.
sberry
Banned
The toilet has a bitty supply tube. A place for large lines is a tub for fast fill but showers are now usually low flow. In the pic above standard is like you have it, with 3/4 mains and has been for decades. Recently energy saver fixtures have drastically reduced demands, a toilet now takes 1.6 over the same time frame it used to take 5 gpm. In my place cannot feel the flush during a shower. You can run the cold 3/4 in the pic above and 1/2 on the hot, makes for faster to the sink.
Use a hair drier to warm the pipe if it needs to conform to a certain path. Before you start shoving it through holes put a plug in the end to keep **** out of the pipe.
Holes should give room for expansion and not have rough edges/splinters.
Use lots of supports/hangers. Use good cutters and a reaming tool
Sharkbite makes some real nice water heater connection hoses with shutoffs. If you use sharkbites buy the reaming and edging tool.
When I have done houses where it still needed to be occupied I used sharkbites as temporary connections to copper, poly b etc. as well as the sharkbite stopper plug.
Holes should give room for expansion and not have rough edges/splinters.
Use lots of supports/hangers. Use good cutters and a reaming tool
Sharkbite makes some real nice water heater connection hoses with shutoffs. If you use sharkbites buy the reaming and edging tool.
When I have done houses where it still needed to be occupied I used sharkbites as temporary connections to copper, poly b etc. as well as the sharkbite stopper plug.
sberry
Banned
That pes page has a huge amount of info in those charts including drops with 2 fixtures etc. Something to note is a couple sets of info, one is basic numbers for drop at 100 ft and another for 60. If one is basing the figures on the long one a 15 ft is going to be substantial difference, about the same with 1/2 as a 3/4 at 100. Distance is a huge factor.
With hot to fixtures we might want to be somewhere in the center of the velocity chart, pressure drop isn't very noticeable till we get at rates above ft per second or so.
If we are doing hand wash at 2 gpm only 1/2 of it is hot we are only serving a gallon a minute or so. Huge difference in speed with a 3/8 vs a 3/4 and so much less pipe to heat up as well as latent water sitting.
A kitchen sink and some bathrooms depending on occupancy can see a fair frequency rate over a long period of time, decades and 10's of thousands of cycles and sizing could lead to efficiency.
More to be gained from this than increasing to lower pressure drop where you would never see saving.
With hot to fixtures we might want to be somewhere in the center of the velocity chart, pressure drop isn't very noticeable till we get at rates above ft per second or so.
If we are doing hand wash at 2 gpm only 1/2 of it is hot we are only serving a gallon a minute or so. Huge difference in speed with a 3/8 vs a 3/4 and so much less pipe to heat up as well as latent water sitting.
A kitchen sink and some bathrooms depending on occupancy can see a fair frequency rate over a long period of time, decades and 10's of thousands of cycles and sizing could lead to efficiency.
More to be gained from this than increasing to lower pressure drop where you would never see saving.
slip knot
Well-known member
Kinda funny to see everyone recommend 3/4 in feeds but dont take into account the supply cutoffs. Look at the inside of these and most are <1/4 in. You can only fill so fast no matter how big the line is.
All of my rentals are redone in Pex the first time they have plumbing issues.
My plumber runs 1in to the house and the cold water manifold. 3/4 to the WH and back to the HW manifold. everything else gets 1/2in. Every application runs direct to the manifold.
All of my rentals are redone in Pex the first time they have plumbing issues.
My plumber runs 1in to the house and the cold water manifold. 3/4 to the WH and back to the HW manifold. everything else gets 1/2in. Every application runs direct to the manifold.
volleyball
Well-known member
I know what size pipes are standard. It is not for the toilet, it is for the shower.
It reduces the pressure loss at the shower when someone flushes. That is why I asked if there was only one person.
You can run 1/2" to 3 fixtures, so the vertical black line can be 1/2" and it will work fine. People wanting to run 3/4" to fixtures really don't know or understand how this works. The stop on the wall will connect to your 1/2" pex and then be greatly reduced like someone stated above. I would only run 3/4" to a water heater, exterior hydrant and a -multi - head shower system.
csp
Well-known member
Length of that small diameter is what though, less than an inch? It's not just the diameter of the hole, but the length that it is ** diameter as well that affects flow and pressure drop.
Beemer533
Well-known member
Why wouldn't you just use full port ball valves?
http://www.supplyhouse.com/Watts-0555110-LFFBVS-3C-1-2-Full-Port-Sweat-Ball-Valve-Lead-Free
slip knot
Well-known member
Yeah, those look real good sticking out of the wall.
How many supply valves are full flow. get real guys.mires
Well-known member
Yeah, those look real good sticking out of the wall.
gatorgrabber
Well-known member
The 2nd edition of the PEX Design Guide referenced earlier really does a good job explaining all of this if folks would just bother to read it. I spent an hour earlier today going through it for my own project. It answers all of these questions and appears well researched. It's an easy read and even has lots of pretty pictures! 
slip knot
Well-known member
Pictures are important for this bunch!!
gatorgrabber
Well-known member
Lots of tables, too...people don't like tables! 
Last edited:
RegeSullivan
Well-known member
I'm in total agreement with the guys that want to use the smallest size pex as long as you are feeding the a manifold system with 3/4" and use home runs to each point of use. It is also important to be as close as possible to the water heater.
I am not sure what the specs are on most washing machines for home use but I would bet a 3/8 home run would satisfy most manufactures specs at 40 PSI or greater but I am sure 3/4" is overkill. Also with long 3/4" run and a modern HE washer you might not get enough HW to fill the machine to the proper temperature. They use very little water compared to an old top loader. The only place I see the need for 1/2" pex is a bath tub and every hose bib. There may be an advantage to 3/4" for a hose bib if you use full flow valves and bibs.
What surprises me is how hard it is to find 3/8 pex fittings and shutoffs. It really cuts down on the wait time for HW but plumbers don't seem to like to stock it so many supply houses carry a limited number of 3/8" items.
I am not sure what the specs are on most washing machines for home use but I would bet a 3/8 home run would satisfy most manufactures specs at 40 PSI or greater but I am sure 3/4" is overkill. Also with long 3/4" run and a modern HE washer you might not get enough HW to fill the machine to the proper temperature. They use very little water compared to an old top loader. The only place I see the need for 1/2" pex is a bath tub and every hose bib. There may be an advantage to 3/4" for a hose bib if you use full flow valves and bibs.
What surprises me is how hard it is to find 3/8 pex fittings and shutoffs. It really cuts down on the wait time for HW but plumbers don't seem to like to stock it so many supply houses carry a limited number of 3/8" items.
Last edited:
Beemer533
Well-known member
Ahh, ok i wasn't thinking when i made that post that you were referring to the shutoffs at the appliance end for some reason. .. Yeah, that wouldn't look all that greatYeah, those look real good sticking out of the wall.
This post edited by the NSA
sberry
Banned
That pex data manual and charts are super, very simple and some of the best I have seen. Its really worth digesting and I have been looking at it off and on for a couple days now and it goes along with my rambling although states it much better.
It puts some math to the simultenous fixtures etc and at modern flow rates both fixtures running at the same time wouldn't be much of an issue and it couldn't hurt to size up the run of cold past the toilet but what I can say from "real world" if you can call it that is that you wont notice it today, do it or not especially on short runs.
The time temp volume data is on 60 ft and much standardized is on 100, its all still averaging but shorter is even better and the numbers go way up when we have a 1/2 run to a sink of 5 ft and another 5 to a washing machine. Replacing 5 ft of 1/2 to 3/4 wont be noticeable in a domestic system especially one with good static pressure which is a factor and maybe a bit more so on well systems that fluctuate, I eluded to some of this in an earlier ramble but in the sink laundry scenario or laundry sink you don't care so much about speed to laundry but if the sink is hi cycle it adds up.
sberry
Banned
Some of this
Test Summary
A summary of the performance characteristics of each system is shown in Table 8.6. The data indicates:
•
Trunk and branch and remote manifold systems will supply one fixture at a higher pressure
•
Home-run systems will supply a more stable pressure to each fixture when operating simultaneous fixtures
•
Home-run systems will deliver hot water to the outlet quicker, especially when the pipes are at room temperature
•
Trunk and branch and remote manifold systems will deliver hot water quicker during
sequential flows
• All three system designs will supply sufficient flow and pressure to the outlets even when
the base riser pressure is 40 psi and the length to the farthest outlet is 100 feet.
Table 8.6 – Performance Summary, 100’ Maximum Distance
Test Fixture
Test Fixture With
Test Fixture
System
Only
Simultaneous
Only
Flow Rate Hot
Pressure Hot
Flow Rate Hot
Pressure Hot
Time to
Last edited:
sberry
Banned
The test summary is important, it draws some conclusions that all work to 100 ft, some are better but if you shorten the distance the math becomes closer and the difference less if that makes sense.
sberry
Banned
The guys plumbing air should look at the charts. Especially with 2 stage comps where the air is being regulated. What is a regulator but a choke, you can do the same thing with a small whip hose. Or can by pass a 50 ft reel with a 10 ft hose for way more power,,, if you need it. With 2 stage as long as the first is as big as the second its working about as good as it can and is easiest tuned with shorter runs.
The home run data and trunk data differ a bit in that if feeds any one fixture better with trunk especially as volume go up and distance increases.
With water even head pressure may mean a lot especially with low kick in of wells and 2 story buildings.
The home run data and trunk data differ a bit in that if feeds any one fixture better with trunk especially as volume go up and distance increases.
With water even head pressure may mean a lot especially with low kick in of wells and 2 story buildings.