gpd meaning in water

RO Water filtration play an important role in our daily drinking, and when we choose a RO water filter system, we often see GPD value on product, so what is GPD meaning in water? Is higher GPD membrane better? Let us figure it out in this article.

What Is GPD Meaning in Water?

GPD is the Unit of water flow rate, Gallon Per Day, we usually use on the Reverse Osmosis water filter. A key indicator for measuring the performance of the water purifier. We take 100 GPD membrane as an example:

It means that the reverse osmosis water system could purify 100 gallons of water per day (24H), which is equivalent to 12 liters of water per hour (1 gallon is approximately equal to 3.75 liters).

100 Gallon x 3.75/24H = 15.6 Litre/H = 260ML/Min

We just talk about basic GPD meaning in water, then let us explain the factors affecting GPD water.

The flow rate (Gallon water produced Per Day) is an important facotor to affect the price as well as the quality of the membrane water filter. The higher the water pressure and temperature, the better effectiveness, and productivity of RO water filter(within the standard range). The actual flow rate in reverse osmosis GPD membrane depends on the water pressure and temperature in your home.

Pressure: the flow rate of the membrane is proportional to the pressure: the higher pressure, the large flow rate.

Temperature: The change of the input water temperature has a great and sensitive impact on the flow rate (GPD)of the membrane. With the increase of temperature, the flow rate of water increases at an almost linear rate.

GPD meaning in water

Why Should We Know the GPD Meaning in Water?

GPD is aim at measuring the flow rate of a membrane, that means, the amount of drinking water per day. The GPD membrane specifications and outlet flow rate are consistent, the higher the specification parameters, the faster the effluent flow rate. we can choose reverse osmosis water filters according to our needs, family members, budget cost.

There are 2 general types of under sink reverse osmosis systems on the market: 50 ~100 GPD RO water filter with tank and tankless RO water filter at least 400 GPD,  let's talk about whether the GPD is the higher the better.

50 GPD VS 100 GPD, Is Higher GPD Membrane Better?

50 GPD VS 100 GPD, the difference between them is the length membrane, the longer the length, the more water it purifiy, so the more water input channels can produce more clean water.

Generally, under constant temperature and constant pressure, the water output of 100 GPD RO Membrane is larger than 50 GPD RO Membrane,

  • 100 GPD 100*3.75/24 =15.6L/H, about equal to 260ml/min
  • 50 GPD 50*3.75/24=7.8L/H, about equal to 130ml/min

So the 50 GPD membrane takes about 2 minutes to prepare a glass of water from a 250 ml cup. That's too slow. In order to sovle this problem, we use a pressure storage tank. The water from the water purification mechanism, first stored in the pressure storage tank, when using water, the water is pressed out through the pressure in the tank, and the water output of the faucet can reach about 1 liter per minute. In this way, the waiting time for a glass of water is shortened to less than 8 seconds, which is more convenient for us. So choosing 100 GPD is more convenient for family membre.

There are also some ultra flow rate Reverse osmosis water filters on the market, generally more than 400 GPD, with tankless RO water filter system.

Why Is the Membrane Flow Rate Designed as 400 GPD?

The 400 GPD RO water filter system can produce 1 liter of water per minute, and this can be accepted by customers. The difference between 600G, 800G, or 1200G RO machines is that the water output speed is faster. It could bring a better experience. With faster speed of water through the membane, the RO machine no longer needs a pressure storage tank.

Is Higher GPD Membrane Better?

Not really. Although high GPD membrane improves the performance of reverse osmosis water filter, it also faces some new problems:

We will spend more money buying a higher GPD reverse osmosis water filter. Compared with 50 GPD water purifiers, the cost of 400G water purifiers increases by at least 60%.

The effluent flow is unstable. Due to the high flow rate, the lifespan of the membrane is shorten than before, the effluent flow will become smaller and smaller with the using time.

50 gpd vs 100 gpd

In conclusion, each of GPD membrane water filter has its own advantages, the tankless RO water filter is convenient, fast, and does not occupy too much space; the reverse osmosis water filtration with tank is cheaper, the flow rate and water quality are more stable, and there is no too high TDS value of the first cup of water. 

Knowing well the GPD meaning in water will help you to make a better choice to buying a water filter system, accroding to the needs and budget. And there is other important conception in water filter system: Water filter micron rating. For more information, you could read this article: What micron filter do I need?