Pex run through attic, Central Florida

[FloridaSlabLeakMonster]

I'm going to bypass the slab leaks. Running Pex A through attic. Plan to put a hot manifold and cold manifold in garage. Run branches to each plumbing element. So 3/4 comes into the house. So I will run 3/4 pex from that point to the garage. Into hot water heater then to hot manifold. And also of course the 3/4 pex runs to the cold manifold. Now, the existing copper manifolds out of garage are all 1/2". Is that what I should do for each branch off manifold...make them all 1/2". Currently on far end of house the shower takes forever to receive hot water. If I ran 3/4 to that shower....would it get hot water faster or would it actually make the problem worse because you have to remove more cold water in the line? Hey any advice is appreciated. I did try to research all of this on here. My thinking is that in a bathroom you have a shower, sink, toilet. The toilet pulls water in for what 30 seconds. You flush...walk to sink. You wash hands. Don't see how you need 3/4 there. The shower having its own 1/2"...should be enough. Kitchen is one sink. Sink in garage. Washing Machine....dedicated line 1/2" for washing machine. Should be good. So I'm thinking 1/2 branches off manifolds. Oh and there are 3 outside spigots. Should I run separate 1/2 lines to each one from cold manifold. I appreciate any help. Thank You.

 

[johnjh2o]

The rule of thumb don,t put two fixtures on a 1/2" line.

 

[breplum]

If you ran 3/4 hot to that distant shower you are correct in thinking that you have to dump more water volume before it becomes hot.
I would recommend a 3/4" trunk and then 1/2" branches and bring the fully insulated 3/4" PEX hot back to the WH plus add a recirculating pump with aquastat.
If the outside spigots are just occasional use hose bibbs, then 1/2" is fine.
IF irrigation is anywhere, use 3/4".

 

[FloridaSlabLeakMonster]

I appreciate the feedback. OK, don't put two fixtures on 1/2". Got it. No recirculating pump. Currently...I can see that out of the hot water heater the 3/4 goes to a manifold in back of hot water heater. 3/4 becomes 3....1/2"lines. With only these 3 lines they are running the entire house. I plan to have 8....1/2"off the hot manifold. Hot Manifold will be 1" Copper. That should be a substantial improvement.