PEX vs PVC

[bevans6]

Apparently it's code in some places that you need to use metal for 18" out of a water heater.  It's allowed direct to the water heater here, fwiw.  My house has 3/4" PEX direct to the water heater.

Edit - I can't even find the metal to pex extensions in any supply house here locally, in the on-line catalogs.  I'm going to look into this further, I have found many many discussions where the manufacturers of the PEX require the metallic extensions.  Looking like a project is in my future...   

Brian

[sledhead]

I used the pex heat line ( 200 f ) from the w/h to the manifold

dave

[bevans6]

Well, I am finding out more stuff.  I went to the BOW website, since I have BOW SUPERPEX in everything here.  This is what they said:

• Bow permits the use of Bow SUPERPEX when
connected to instantaneous water heaters or
other hot water producing devices. However,
consult manufacturers recommendations for
use with plastic tubing and ensure temperature
and pressure do not exceed the maximum
ratings of the SUPERPEX tubing.

When connecting to a gas hot water heater, at
least 18 inches of a metal nipple or appliance
connector should be used so that the SUPERPEX
pipe cannot be damaged by the build-up of
excessive radiant heat from the flue.

SUPERPEX can be piped directly to the heater
tapping on an electric hot water heater using
metallic termination fittings.

My hot water heater is a powered vent propane gas heater, so the flue is piped with white ABS plastic and does not get hot to speak of, so apparently the restriction due to excessive radiant heat from the flue pipe does not apply in my installation.  In my bus, the gas heater is obviously outside on the other side of the tank from the water connections.  It is allowable to connect BOW Superpex directly to an electric hot water heater, so the issue is not the heat of the water itself.

My daily dose of education due to the Bus Conversion forum, I would say!   

Brian

[eagle19952]

Well, I am finding out more stuff. 
My daily dose of education due to the Bus Conversion forum, I would say!   

Brian

I would not use PEX or anything but copper or iron there ... Glad I could help ... 

[luvrbus]

HD and Lowes both sell the adapter from the hot water tank to the PEX they are not cheap but required here by the county code even on electric water heaters

[Oonrahnjay]

HD and Lowes both sell the adapter from the hot water tank to the PEX they are not cheap but required here by the county code even on electric water heaters

     Yep, hot and cold sides.   $37 wasted IMO ...

[Fred Mc]

I just made my own 18" extension using copper tube, and a copper to pex adapter. Cheap and easy.Probably cost under $2

[eagle19952]

     Yep, hot and cold sides.   $37 wasted IMO ...

Ah... the code mostly cares about the die-electric/insulating property of the connection.... it is to keep your wife/kid/yourself from getting shockacuted when the element or ground or whatever fails and your hot water heater becomes a shock box....