Quote Originally Posted by denanbob
What does vac to waste mean? I've seen this several times and I'm trying to figure out what it means. Can anyone help a newbie? Thanks!
Normally, when you vacuum a pool, you plug the hose into the skimmer or the low drain and the pump sucks all the junk out of the pool while you vacuum. You can either direct that dirty water through the filter and let the filter try to clean it (and if some of the dirt is too small it may not) or you can redirect the water to a drain--to waste. Some filters, like sand filters, have a valve on top that allows you to:
1) filter the water
2) simply circulate the water and bypass the filter
3) backwash the filter (force water through backwards knocking the junk loose and directing it to a drain)
4) go directly to the drain and not filter it.
5) block off the filter and pump.

There's a 6th position but I don't remember what it is.

Some filters, like cartridges, don't have a valve like this and you must either open a port on the bottom or just plan on cleaning it.

You can also vacuum to waste by syphon if you can get the hose end outside the pool lower than the pool bottom. The natural syphon acts like a vacuum and by definition vacuums to waste.