My 11 yr old black lab drinks but won't eat much food he didn't eat today but eat yester day he heats evry other day this started Monday don't know why but it was after he came in from out in our back yard

Ohhhh take Boo boo to the doggie doc if he doesn't eat real real soon. Animals/pets, our "other" children can become sick just like human children. They cannot tell us what is wrong. But you know your kid. You know your pet. You wrote here looking for help or advice and that says a lot . You know your lil' baby might not be feeling okay. Please keep a close eye on him as I know you will but don't wait too long please if he doesn't eat real real soon or seem normal to ya' okay? Best wishes and bless you!

Is he vomiting or having bowel movements?

Not wanting to eat and drinking loads of water in an 11 year old dog is need to be concerned. Your best option is to get him in for a check-up and possibly bloodwork to check for metabolic problems. Older dogs can suffer from kidney and liver issues, diabetes, stomach problems, and the list goes on.
I hope that is not the case with your dog, but don't let this go on too much longer without getting him checked out.
Good Luck