On 7/13/2011 2:21 PM, Peabody wrote:
I have a pool, and use an ancient Guardex "open" chlorinator that
takes 1-inch trichlor tablets. But I can't get parts for it
anymore, and every now and then the check valves get crud in them,
and overnight when the pump is off I lose prime. So it may be time
to get a new one.

All the modern chlorinators appear to be sealed systems. There are
input and output ports, and there's a screw-on lid that I assume is
air-tight. But I don't understand exactly how these things work.
What determines how high the water level gets inside the
chlorinator? Is there any way to adjust that? I assume it doesn't
fill up completely, but there's some air in the top.

The other issue I'm concerned about is that I only run the pump
about 12 hours a day. And I wonder what happens to the chlorinated
water in the chlorinator when I turn the pump off. Does it stay in
there and continue to dissolve the chlorine? In my old
chlorinator, the water drains out when the pump turns off, and I'd
like to keep that feature if possible.

The sealed systems require a check valve between the filter and the
chlorinator to prevent the concentrated chlorinated water in the
chlorinator from going back into the filter and pump. There is no
benefit to draining the water from the chlorinator, and it's not
possible to do so. Don't forget that the chlorinator needs to be
installed in the proper flow direction!

As someone else pointed out, the first few seconds after the pump starts
you'll get a burst of highly chlorinated water into the pool, but it
doesn't hurt anything.

The Pentair Rainbow filter has another advantage over the Hayward, you
can add extensions to increase the number of tablets it will hold,
http://www.yourpoolhq.com/extension-chlorinator-10in-r172087.html. I
have one extension on mine. If you're going away for more than a few
weeks it's useful. When I go away now I first super-chlorinate the pool
with liquid chlorine than fill the chlorinator with tablets and keep the
level pretty low. As long as the phosphate level is zero, the chlorine
level doesn't have to be maintained very high to prevent algae.

If you really want to automate the sanitizer delivery to the pool then
the solution (no pun intended) is to switch to a salt system. There is a
high initial cost for the salt system, and periodic salt cell
replacement, but additional salt is not needed often. This won't work if
you have any copper plumbing in the pool or in a pool heater.