Where the repeat revenue is
A system sells once. The cartridge and the membrane sell for as long as the system runs: the cartridge once a year, the membrane every two.
Two consumables carry the revenue: the combo cartridge and the RO membrane. On the under-sink platform both have fixed part numbers (LXL-A0002 for the cartridge and LXL-A0001 for a 100 GPD 1812 element, one per system), which is what makes stock-holding on that platform simple.
Per installed system that is one cartridge a year and one membrane every two years, and more on hard water, where both wear faster. It is the figure worth modelling before quoting a rollout.
Before you quote a commercial model
Commercial models use different elements: a 100 GPD element does not serve a 600 or 1000 GPD machine. For anything above the under-sink platform, contact us to confirm the correct parts and quantities, and include them in the quote rather than leaving the customer to discover them at the first service.