Not sure what you mean by 'what to use to seal'. Rona, Home Depot, Corix, Ocean and Bulk all sell cement.
Home depot/Rona are fine for small quantities of elbows/tees etc.
Bulkreef Supply online or
Corix for schedule 80 unions, Gate Valves and True Union Ball Valves. Also
Ocean Aquatics or
J&L Aquatics for Gate Valves.
Also, Rona has schedule 40 pipe, Home Depot only has 200 which is thinner but stupidly the same price.
Most of these places sell Bulkheads.
Make sure you spend the extra money and use Sch80 Unions as they have a larger ID.