Welcome to the Forum, Wendy!

Backwashing to waste is only an option for sand or DE filters with a multiport valve, cart filters don't have them.

There is usually a way to "~ vac to waste" for cart filters, but how to do it depends on which model filter you have and how your plumbing is set up.

If you can tell me a little more about your filter (manufacturer and model) and plumbing, I can probably tell you a way to bypass the carts while vacuuming (a pic of your equipment pad would be optimal, but you aren't allowed to post pics yet)