I was at a building supply store yesterday, and had time to spare. I
grabbed a roll of 1/2" PEX and a stick of 1/2" copper pipe. I held them
end to end. The OD is about the same, but the ID of the PEX is about
15% or 20% smaller, because the walls of the PEX are thicker. This
means that there will be less water available at the fixture, when using
PEX. For most fixtures, such as a sink or toilet this is likely not a
problem, becuase those fixtures usually have a 1/4" supply tube feeding
that fixture anyhow.
But for a bathtub. washing machine faucet, or an outdoor spigot, that
would make the flow slightly less than with copper or steel pipe.
(Probably 15 or 20% less, since the pipe is that same amount)
But it gets MUCH worse. The fittings for copper or steel pipe are
always LARGER than the pipe itself. The fittings for PEX are SMALLER,
since they fit inside the pipe. I grabbed a 1/2" brass PEX fitting from
the shelf and looked at the ID of the hole inside this fitting. The ID
of the fitting is just a tad over 1/4". Thus, about 50% of the ID of
rigid copper. That is a significant difference.
While feeding a toilet or sink from 1/2" PEX may be acceptable, I'd find
the amount of water at a bathtub, washing machine and particularly an
outdoor spigot to be less than desirable.
I dont think any of you PEX lovers can argue with this. Facts are facts
and a 1/4" hole inside of a PEX fitting is only going to allow 50% of
the water flow that a 1/2" copper pipe will allow, (which is just a tad
less than 1/2".)
I think this explains the reason that PEX pipe is supposed to be
installed using a manifold, whereas each fixture has it's own pipe.
This manifold system may be perfect for new construction, where there is
a basement and easy access inside walls to install everything. But to
daisy-chain pipes, from room to room, seems like the result would be
completely unacceptable. And in places that have no basement, and the
plumbing is being replaced in an existing building, running a huge
bundle of pipes to distribute to all the fixtures in the home would be
I guess the only way to use PEX, still have adaquate water, and daisy
chain the pipes would be to use 1' or larger PEX as the "feed pipe" and
use 3/4" for everything else. (This would allow about the same flow as
using 3/4" and 1/2" copper or steel pipe, which is common in homes).
This fact alone is what made my final decision to NOT use PEX in my
home. I MUST daisy-chain my pipes, since there is no basemnt and some
pipes will be exposed. Having two exposed pipes (hot andd cold) is one
thing, but if I used a manifold system, I'd have 14 pipes exposed at one
location. (NO THANKS)!
I did check into using 1" PEX but those fittings are even more costly
and would require buying TWO crimping tools, since most of those tools
are either ONE SIZE ONLY, or fit 1/2" and 3/4" combined, but not 1".
Plus, I will have several outdoor spigots attached and I need adaquate
Even if PEX is great pipe (as some people seem to believe), you can not
deny that the fittings are TOO SMALL for some uses. Why they do not
make fittings that fit over the OUTSIDE of the PEX (to eliminate the
restrictions), I will never know...... I suppose there is just no way
to attach them.....