I’d very much endorse what JimD said. In particular, think hard about ‘what level of detail do you want to work in’?
Some pre-made components, either from manufacturers, or on the 3D warehouse, use grossly excessive numbers of segments in circles, and far too much other detail in their models. When incorporated into assembly diagrams, they bloat the model, especially if they are not made from components or groups.
Remember at what degree of close up you will be viewing your final drawings, and limit the details in pipefittings and pipework accordingly. For the pipes, you probably don’t need to model the wall thickness (simple cylinders may do the trick) and you will probably not need the default 24-segment circles for your pipes - try 12 or even 8. Make sure that the segment number is the same for all pipes and all fittings (if you draw them yourself) - it’s a nightmare to try to join, in 3D, a 16 segment pipe to a 24 segment fitting, and even if you manage to align it centrally, the junction will look wrong. Put construction points at key locations like pipe end centres, flange centres, etc.
For an example of simplification applied to standard scaffolding fittings (drawn with minimalist 8-segment circles) see my drawings at Scaffolding clamps - dynamic components | 3D Warehouse
And try TIG’s plugins PipeAlongPath or TubeAlongPath to draw the pipes more easily than just using the native FollowMe tool, as well as a Points plugin (e.g., PointTool) to make drawing construction points easy. You can get them at no cost (after free registration) from the SkectchUcation plugin store.