We had to learn the HARD way that Polyproplyne is NOT "forever" with Chlorine.
Our John Blues leaked, manifolds cracked, and EVEN the pumps we NOW use finally started biting it.
The Cole Parmer Chemical Compatability Database SHOWS Polyproplyne as having an "A" rating against Chlorine's harmful effects.
But, in practice it does not.
Because every manufacturer uses GLASS Filled Poly, to strengthen it against the Pressure.
What is really need is KYNAR.
Our NEW pump is made out of KYNAR, with Teflon diapraghms and ball valves.
You live, you learn.
IMHO, between a Comet and John Blue, I would take the John Blue hands down.
Because John Blue listened to me what I contacted them in Italy!
I suggested Hastelloy springs, valves, and retainers.
They were scared it would push the price way up, and it would not sell.
Instead, they made the check valves EASY to change!