Copper Connections with PEX

I am doing a bathroom in the basement of my house. I have to run 4 cold and 3 hot (tub, sink, shower, and toilet). I am going to be coming from 3/8 ID, 1/2 O.D. Copper. I bought 1/2" PEX to run under the concrete floor, I already have it broken up. I am using PEX because it's seamless (zurn pex). From the copper lines off the water heater (hot) and softener (cold) I am just going to cut out about 12 inches and add reducers to bump it up to 1/2 I.D. 5/8 O.D. copper, because not only is this the same size as the 1/2 PEX but also everything is cheaper in this size, maybe because its standard. So I will cut into the 3/8 copper lines and add reducers to a 1/2 inch line with 4 tees in the cold line and 3 in the hot. Off the tees, I will continue with 1/2" down about 2ft from the ceiling (which is where the copper lines are running off the softener and water heater) to a 1/2 ball valve, continuing in copper again with a zurn pex copper to pex fitting at the end. This is my first project with piping and it's quite a big one. I fill fully confident I am able to do this just fine. My only problem is every time I talk to someone about it, I am told a different way how to do it. Even the guys at the hardware store have told me 3 different ways to do it. The first time I had all threaded fittings with compression for the copper. The second time, I had flare fittings with threaded couplings, the third time, its now all solder fittings, no threads except where the pex connects to the copper, that is some sort of compression fitting, no choice I guess there. I feel this is the best way, soldering everything, rather than compression, flaring, or threading everything together, do you agree? Also, I am teeing into the main 4" sewer line (stack) for all the drains. I have it dug up and ready to cut. From what people have told me so far, I should come off the 4" sewer line which is about a foot below the basement floor with a 4x4x4 Y and then have 4x4x2 tees off of that going to the various drains, reducing to 1 1/2 when needed. And also reducing to a 3" for the toilet. Or someone told me I could just reduce to 3 from right off of the sewer (4x4x3 Y) and go to 1 1/2 right off the 3" line (3x3x1 1/2). Which is better, isn't bigger better? Thanks
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snipped-for-privacy@hotmail.com wrote:

Phew. How odd that the existing lines are 1/2" O.D. Most unusual. Oh, well.
Sounds like all your soldered copper fittings will be above the floor. Then PEX below the slab. Sounds OK.
On the drainage: I think you should be talking to your town/city inspector; you may be headed for trouble.
My take on it: Use the 4X4X4 WYE to enter the existing house drain. (4X4X3 WYE will work too, but that decision rests with the inspector.)
Use an appropriate-sized WYE (or long-turn TEE-WYE) for each fixture branch; never use a SAN TEE in this kind of app.
Now, each fixture trap must be protected by some form of venting arrangement. Here is where is gets sticky, especially working under-slab. I would get a good book at the library or BigBox on DIY plumbing and study it. Then talk to the inspector to see what he will allow/require.
Jim
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ABOUT the 1/2 O.D. everywhere, the water comes in at 1/2 I.D. then off the water heater and off the softener it reduces to 3/8 I.D. lines about 6" from the outs from there. Also why are you saying use long turn tees? Just curious, whats the difference between that and a regular y? For venting I just planned on using "quick" vents, they are about $5 and allow airflow in but not out. Thanks!
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snipped-for-privacy@hotmail.com wrote:

Ok, it's whatever it is.
Also why are you saying use long

Long turn TEE WYE is useful because it gives you a rt angle entrance with a gentle sweep. That or a plain WYE will work if the layout fits.
For venting I just planned on using "quick" vents, they are

Yah, they are handy, but I doubt that they would be accepted. Maybe you're not subject to inspection, so that's your call.
1/4" slope per foot and you'll be fine:-)
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Ok, no tees, just y's, I understand, I will stick with the 4x4x4 and 4x4x2 y's, if permitted, I will use long y's, Thanks for the tips! I dont know if quick vents are permitted either, but it sure is strange how the guys at the lowes can tell you to use this stuff then it not be permitted by the city. Reminds me of the ventless gas fireplace I have in my basement, I was told by my gas meter reader when he checked the meter one time that I wasn't allowed to use it, against code or something, but they still sell them at menards, lowes, etc... You can buy em, just can't use em? I think if your not suppose to have them, they should put restrictions on selling them in the area. I understand the risk of a ventless fireplace but its made that way, and what can you do about it. I never use longer than two hours at a time in the winter.
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