Impeccable professionalism, very friendly, did a fantastic job! i would highly recommend pat's plumbing! Make sure your boiler is fully serviced and covered by our guarantee by picking from the following options. Len the plumber is a full service plumbing and drain cleaning company serving the entire baltimore, washington d.c., northern virginia, delaware and the philadelphia area as well as. Boilers installed in the uk are required to be condensing boilers these are.