A water treatment installer can only work with what is in front of them when they arrive. If the main shutoff is hard to reach, the drain route is unclear, or the space is full of stored boxes, the crew loses time, and the job can end with a return visit. Most of that can be settled before the appointment, and the questions below are the ones worth asking while you still have time to act on the answers.
Confirm the water shutoff
Find your main shutoff valve and turn it by hand before the installer comes. Note where it is, whether it turns freely, and whether it fully stops the flow when closed. An older valve can stick or leak when it is moved after years of sitting still. If it does not close fully, tell the installer before the day so they can plan for it, and ask whether they will need to add a shutoff or bypass as part of the work. Ask them to show you where the new equipment will sit relative to the shutoff, so you know which valve to use if something goes wrong later.
Settle the drain route
Ask where the system's discharge will go. Common options include a floor drain, a utility sink, or a standpipe, and each has its own requirements. Ask the installer to point to the exact spot they plan to use and to explain how the connection will be made and protected from backflow. If the drain is far from the equipment, ask whether the route will run along a wall, through a finished area, or across the floor, and who is responsible for any patching afterward. Write the answer into the quote or the work order so it is not left to memory.
Check power and placement
Most systems need a nearby outlet, and some controls or pumps need a specific supply. Ask the installer what they need from you on this point and whether they will bring an extension or need a dedicated outlet installed by a licensed electrician. Do not assume an existing outlet is suitable. Also ask what clearance the equipment needs around the tank or cabinet for servicing, since a unit pushed into a tight corner is harder to reach later when a cartridge or resin needs attention.
Clear the path and plan for water downtime
Clear a route from the entry door to the equipment location and the water shutoff. Move furniture, stored items, and anything fragile out of the work area, and secure pets and children. Ask how long the house will be without water during the job and when it will come back on. Ask who will restore the water, who will check for leaks at the connections, and whether they will run a short test with you present before they leave. If someone else is letting the crew in, make sure they know the plan and have the contact information for the installer.
Decide who signs off
Name one adult who will be home for the appointment, can answer questions, and will sign the completion paperwork. That person should walk the work area with the installer before the crew leaves, look at the connections, and confirm the drain route and shutoff are where they were promised. Use the answers you gathered this week as the checklist. If something the installer agreed to is missing at sign-off, it is far easier to address it while they are still on site.