[VAC] Re: pex size

["Mr. Joy H. Hansen" <joytbrew@xxxxxxxxxxx>]

Hi All,

I've followed the thread for a few days and thought I'd put my two cents in
for consideration.  The '69 Safari had mostly 1/2 inch copper tube for the
main runs and dropped to 3/8 for some sink and 1/4 for others.  Lots of
special reducers, etc. all to what I purpose I think was weight reduction
and flow.

PEX solves the weight consideration as it's feather light as
compared to copper.  Flow is an entirely different consideration.  While the
copper transitioned from 1/2 to 1/4 without restrictions, PEX has a bottle
neck each time a compression fitting is installed.  The actual internal
diameter might be 1/4 inch reduced from 1/2 inch.  Put many of these in the
plumbing and it could drastically reduce the flow in some locations.  This
is a do as I say, not as I did with the Safari or Argosy plumbing.
Especially since I opted to use a ton of "T" and "elbow" fittings rather
than just bend the PEX.  The flow at the galley, toilet, and bathroom sink
are adequate, but not super high volumes.  At the shower head, the amount of
delivery won't win any prizes unless water conservation is the goal. :)

I realize that using 3/4 PEX and reducing it to 1/2 might seem like a bit of
overkill; however, it seems to me that the delivery at any point in the
system would always be adequate.  In my case, it would require the purchase
of a second $100 compression tool to mix 3/4 and 1/2 inch PEX.  Look at the
inside diameter of the ball valves and fittings while you make choices of
plumbing size.  Cheap valves use very small inside diameter.  I try for the
largest available as it varies by brand and country source.  Might be a few
dollars difference to install the larger size.  For a large trailer with
long runs, the size of the PEX might be critical.

It's my opinion that 3/8 PEX is entirely too small when considering valves
and fittings where the inside diameter might be as small as 1/8 inch!  Guess
an engineer could explain the situation with a discussion of fluid dynamics
or something.

Just my opinion and it's worth what it cost.

                                   Cheers, '74 Argosy, 69 Safari, Joy