Either 50GPD, 100GPD or 400GPD are RO membrane’s water flow specification, Some people mistakenly believe this is the daily capacity. In fact it is a common mark for distinguish. Here is how we calculate this specification:
- We make the 400GPD RO membranes filter water for 5-10 minutes.
- Measure and calculate the water volume: 0.278 gallon per minute.
- Further Calculation: 0.278 gallon × 60 minutes ×24 hours ≈ 400 G
Another fact is no one can measure and state a precise amount of daily water filtration and lifespan of RO membrane. It’s all depending on your using habit and source water quality. Now you may ask why we reference 18-24 months?
The PG-400-AZ is designed for household drinking water demand, For a 5 people family, normally it is 1-2 gallons a day at most. And we believe the RO membrane will last for 18-24 months under this daily capacity. Of couse, occasionally you still can get 20 even 40 gallons water in hours, But long-term overload using is bad for RO membrane.
Even though we couldn’t announce a guarantee on all 4 filters. But if you are using it only for drinking and the filters somehow went wrong, we will send new filters for free. You can contact us with firstname.lastname@example.org attached your Amazon order ID to get new replacement filters.