My brother-in-law 63 had radical throat cancer surgery 7 years ago. The radiation has damaged his esophagus to the point he nee ds a feeding tube in his stomach. No saliva, constant water but this and food goes into his lungs causing pneumonia regularly

See Below. If he has a feeding tube and does not eat or swallow anything by mouth, he may have regurgitation of stomach contents into the esophagus/throat area that are then being aspirated into the lungs. Consult with a physician about this matter. They may need to move the tube to the small intestine instead of the stomach to prevent this from happening.
What . What precisely can be done will depend of the condition of the tissues in the neck. Most academic medical centers in the country will have specialists who could deal with this problem. Perhaps they can interpose a portion of the small intestinebetween the pharynx (just above the vocal cords) and the more normal esophagus further below. It will be important that there is no recurrent cancer in his throat.