My husband is in a alcohol/drug rehab facility for his third admission. Can he be served divorce papers there?

Unless there are rehab or hospital rules that differ from the norm, service should be possible. Generally along with being served at home a defendant may be served where he or she is physically found. Many people use this to have a defendant served at their job. I believe that as long as they can put the papers into your husband's hands in the rehab facility, or an appointed agent for him at the facility, then it should be adequate service. Regardless, it sounds like there may be many moving pieces to your divorce and you would likely benefit from talking to a lawyer. Many provide free consultations, so I'd suggest you try the "find a lawyer" tool on this website. Best wishes moving forward.

Yes you should be able to serve him there. Do you have an attorney handling your divorce? If so you need to get an attorney.

Yes he can be served at the rehab facility if they will allow admittance onto their property for service of process as they may not. I would speak to the sheriff's department if you are using them or the private process server you hire and make sure he can be served there before you pay the fee. That is because since this is a private facility, they may not permit entry onto their property for him to be served.

He may be served where ever he is found except that he may not be served while attending court.