A dog-grooming or pet-wash room in a house does not add people. It adds a bath schedule. One person showering each morning is a steady, small draw. A Saturday when you wash two large dogs, rinse the tub, and run a sprayer or hose station can pull a large share of a normal day's water into a few hours. That spike, not the headcount, is what the softener has to be sized for.
Ask for the bath schedule, not the household size
When a company sizes a softener from a headcount, it is guessing about the people. A wash room changes the pattern, and a headcount check will miss it. Write down the real numbers: how many baths you run in a typical week, how many animals go through in one session, whether two sessions ever run back to back, and whether the water passes through a hot line that the water heater has to refill. Give those numbers to the installer and ask them to show the daily volume and the hardness they assumed. If they cannot show the math, the size is a guess.
Check the regeneration trigger against bath day
Ask whether the unit regenerates on a fixed timer or on metered use. A timer can start a regeneration in the middle of a wash afternoon. A metered unit regenerates sooner after a heavy bath day, which is the right behavior, but it means the regeneration time moves around. Ask the company what happens on a day you wash unexpectedly, and whether the regeneration can be set for an overnight hour. Have them write the final setting on the unit's record so the next technician starts from the same place.
Decide which line feeds the wash station
Before you size anything, decide whether the wash station should get softened water at all. Some owners route the wash tap to the softened line so the water matches the rest of the house. Others keep it on the untreated line so the heaviest-use fixture does not draw down the softener's capacity. Neither choice is correct by default. Make the choice on purpose and write it on the plan so the installer does not route by habit. The plan should name every fixture on each line, the same way a whole-house plan does.
Plan for the drain and the hair
If the wash station drains to the same floor drain or line as the softener's brine discharge, ask how the two will share it and whether that line has room for a heavy bath day. Hair, lint, and soap are a drain problem a softener cannot solve, so ask whether the wash room has its own catch basket. That part is a plumbing job, and it belongs on the same quote so nobody argues later about whose fix it is.
What to compare on the quote
Put these items side by side on each quote: the bath-day volume the company assumed, the hardness they measured or accepted, the capacity between regenerations under that volume, the regeneration timing rule, the line each fixture sits on, and whether a water heater check is included. Items missing from one quote and present in another are the real difference, more than the headline price. For how we weigh these details across companies, see How We Rate Water Softener Companies.
Keep the plan honest after install
Keep a simple log of wash days for the first month, then compare it with the sizing the company assumed. Tell the company if your schedule changes, especially if you take on more animals or add a regular client. Ask them to recheck the sizing against that real log rather than the original estimate, and to adjust the regeneration setting if the pattern has shifted.