Specifically, a standpipe for use in the crawlspace, not for use on the floor above. Sorry I wasn't specific.
To be more specific, Id like to drain my backwash from my back washing filters to a dedicated stand pipe in the crawlspace. The units will be located there. The stand pipe will be the highest drain on the vertical soil stack if it matters (no other drain higher than it..thus all vent above it...all other drains tied in below it)
The only other real option is to plumb a drain over an unconditioned closet off the back of the home. It's where the old water heater used to reside.
Since I'm located in the Northeast I don't think that's such a swell design either.
This closet is also on grade compared with the rest of the home so the drain itself still wouldn't be much higher than it would be in the crawl and would still be the lowest drain opening.
804.1 All plumbing fixtures or other receptors
receiving the discharge of indirect waste pipes shall be
approved for the use proposed and shall be of such
shape and capacity as to prevent splashing or flooding
and shall be located where they are readily accessible
for inspection and cleaning. No standpipe receptor for
any clothes washer shall extend more than thirty (30)
inches (762 mm), nor less than eighteen (18) inches
(457 mm) above its trap. No trap for any clothes
washer standpipe receptor shall be installed below the
floor, but shall be roughed in not less than six (6)
inches (152 mm) and not more than eighteen (18)
inches (457 mm) above the floor.
UPC Plumbing Code
A standpipe that is too long can siphon.