Before the crew packs up, the condensate line deserves a walk of its own. On a central cooling system the evaporator coil sits indoors and sheds water as it works. A pan under the coil collects that water and sends it out through a drain line. A high-efficiency furnace makes condensate too, from its secondary heat exchanger, so the same questions apply on the heating side.
Trace the route from start to finish
Start at the pan or the furnace drain port and follow the line to where it ends. Look for a steady fall in the direction of the outlet. The line should not sag into a low point where water can sit. Check that every joint is fully seated and fastened, and that the line is supported so the fittings do not carry its weight. Where the line runs through an unheated space, confirm it has insulation, because a cold run can freeze and push water back toward the pan.
Check the safety float and the termination
Many installs include a float switch in the pan that shuts the system down when water rises past a set level. Ask the installer to show you where it is, how it is wired, and whether it was tested during start-up. Then look at the far end of the line. It should discharge to a visible point such as a floor drain, a utility sink, or an approved outside termination. A line that ends in a dead space, or that ties into a drain that can back up, is a question to settle before the job closes.
Ask about the condensate neutralizer
Condensate from a high-efficiency furnace is acidic. Local codes or the appliance maker often call for a neutralizer cartridge in the line before the water reaches a drain. Ask whether one was installed, where it sits so you can reach it, and what the maker's guide says about how often its filler material should be changed. Write that interval in your file alongside the install year. Who replaces the cartridge is part of the same question. Settle it on the day of the job, not when the cartridge is spent.
Run it and watch the pan
Ask the crew to run the system through a full cooling cycle and a full heating cycle while they are still on site. Watch the outlet and the pan during each run. Clear water should move steadily out of the line. If the installer can pour a small amount of water into the pan at the access point, ask them to do it, so you can see the float respond and the line carry the water away. Do not take a verbal assurance that it drains fine. Ask to see it.
What to compare on paper
Look at the install drawing or the job sheet. It should show the drain route, the termination point, the float switch, and the neutralizer if one applies. If the drawing shows a route that differs from what was built, ask for a corrected sheet. Keep it with your owner's file, along with the model and serial record and the install year, so the next person who opens the cabinet knows where the water goes.
Where the contract fits
Service contracts and warranties usually ask about the condition of the system at the start, and many also ask whether the installer's work followed the maker's instructions. A clear drain route and a written note of the float and the neutralizer make that question easy to answer later. The general rules for reading the terms are covered in the site's contract guides, and the published figures are kept on the site's own tables. For planning the timing of a full replacement, see the central air conditioner page or the gas furnace page for typical service life.