Congratulations, Lois1, way to go, and I am sure he really enjoys being a big boy and being able to communicate! It boosts their self esteem tremendously!
Both of my kids used signs for communicating ( including potty) before they were able to talk.
My both kids had their own sign or motion invented for communicating the need to go potty. With the first one it was because I did not hear of baby signing at the time she was born ( and did not know anything about that), but she really wanted to communicate, and by 2 weeks was so clear in showing the need to go potty. At first 2 weeks till about 4 months, she was just using a certain body language to communicate her need - squirming, fussing and waiting till we put her on the potty, then being instantly happy. Then around 4 months she invented her own potty sign, that she used ever since till she started talking.
With our second child ( boy) -- we also used sign language. However, because we were travelling in Europe ( where ASL sign for potty is offensive hand motion
we also invented our own sign). At about 14 month he stopped signing it though and preferred to just say "potty".
But all in all, I think sign language is great asset in Elimination Communication.