What Paul said. In our tank applications (and most applications). Primer isn’t necessary if the pvc is relatively clean. If you’re worried get clear primer like Paul said.Assuming you're using this on your aquarium and not the plumbing in your house.....As Bob @radiata mentioned, the purple is a code requirement to show the inspector that you've used the cleaner/primer. You can still purchase clear primer, but if you simply dope up the pipe and the fitting with the glue, you're good to go. I prefer giving the pipe a quarter turn once it's inserted in the fitting to assure the glue is thoroughly spread around the pipe/fitting.