On Sat, 25 May 2013 11:44:42 -0700, DD_BobK wrote:

Get some Buna-N's from McMaster ...

OK. Makes sense. Pool water is practically drinking water.
I'll go with the basic 50-cent Buna-N (aka Nitrile) o-rings then.

For accuracy, the one thing I need to better understand are
what the trade sizes actually indicate.

The trade sizes don't seem to follow any obvious rhyme
or reason.

For example, the tiny drain plug o-ring is a 0-39 but the
much larger basket cover o-ring is a 0-12 while the slightly
larger seal plate housing o-ring is a 0-240 and the hugely
larger filter body o-ring is a 0-486.

They don't follow any order that I can discern.

Is the o-ring trade size merely from an arbitrary lookup table,
or is there a definable logic to the trade-size designation?

- ~1" drain plug o-ring (x2) U9-359; trade size O-39
- ~3" diffuser o-ring, U9-37A; trade size O-83
- ~3" filter union o-ring U9362, trade size unknown
- ~2" pre1998: Insert o-ring U9-376; trade size O-113
- ~10" trap cover o-ring, U9-375; trade size O-12
- ~12" seal plate housing o-ring, U9-228A; trade size O-240
- ~25" filter body o-ring 24850-0009; trade size 0-486