How Many GPD Do You Need? An RO Capacity Guide for Distributors (100–1200 GPD)
By Li-Men Editorial Team · October 23, 2026
What GPD means
GPD stands for gallons per day: the amount of purified water a reverse osmosis (RO) membrane can produce in 24 hours of continuous operation. Many Chinese manufacturers write the same capacity as "100G", "400G" or "800G"; the "G" also means gallons per day.
For the end user, the most useful figure is not gallons per day but litres per minute at the faucet. That number decides whether filling a pot takes seconds or minutes.
From GPD to litres per minute
The rated flow rates on our specification sheets are:
| Capacity | Rated flow | Approx. time to fill 1 litre |
|---|---|---|
| 100 GPD | 0.26 L/min | ~3 min 50 s |
| 400 GPD | 1.05 L/min | ~57 s |
| 600 GPD | 1.57 L/min | ~38 s |
| 800 GPD | 2.1 L/min | ~29 s |
| 1000 GPD | 2.6 L/min | ~23 s |
| 1200 GPD | 3.2 L/min | ~19 s |
Actual flow varies with inlet pressure, temperature and water quality at each installation, so check each model's pressure range; for example, C03, C04 and C05 specify an applicable water pressure of 0–0.4 MPa.
Tank or tankless
At 0.26 L/min, a 100 GPD system usually works with a pressure tank, which stores purified water and releases it faster when the faucet opens. Our 100 GPD models come with 2.5, 2.8 or 3.2-gallon tanks.
From 400 GPD upwards, direct flow is fast enough to go tankless: water is purified on demand and the unit takes less cabinet space. For a deeper comparison, see Tank vs Tankless Water Purifiers.
Pure-to-waste ratio
Reverse osmosis always produces some reject water. On our multi-capacity models (for example M11 and M12), the stated ratios are:
- 100 GPD: 1:1
- 400 GPD: 1.5:1
- 600 and 800 GPD: 2:1
A 2:1 ratio means roughly 1 litre is discharged for every 2 litres of purified water. In markets where water is expensive or scarce, this can be as strong a selling point as flow rate.
Which capacity for which customer
A practical starting point for your range:
- Small homes or drinking water only: 100 GPD with a tank. Entry price and simple maintenance.
- Families who also cook with purified water: 400–600 GPD tankless, at 1.05–1.57 L/min.
- Large families, small offices or customers who value speed: 800–1200 GPD, at 2.1–3.2 L/min.
- Restaurants, offices and high-demand sites: commercial systems from 800G to 3600G, such as D12 and D13.
Most distributors don't need every capacity. A two- or three-tier range, for example 100 GPD with tank, 600 GPD tankless and 800–1200 GPD high-flow, covers most demand and keeps spare-part stock simple.
Ordering and customization
All standard models start from 10 units. Adding your logo to the machine starts from 50 units, and custom front panels, housings and color boxes have their own minimums. Voltage, frequency and plug type are configured for your market. See our FAQ for details.
Models to compare:
- 100 GPD with tank: M29-RO100, C04
- 100–800 GPD multi-capacity: M11, M12
- 800–1200 GPD high-flow: M04
- Commercial: D12
- Full range: Under-Sink RO Water Purifiers
Have a market and quantity in mind? Send us your inquiry with your destination country and the capacities you need.
