RO water system benefit/consumption

[dodidoki]

I bought one....I am disappointed. I build it as it is wrote in manufacture book. RO water cames drops by drops, unusual "side" water flows out continously....it will be VERY expensive!!!!

 

[Ray]

That does not sound like it is performing correctly, but more details would be needed before that can be judged correctly.

A "standard" residential system, used at the conditions at which they are specified (65 psi [450 kPa], 77°F [25°C] incoming water pressure) should put out 3-4 units of flush water for each unit of pure water produced.

If the temperature is lower, the membrane will be more restricted, so less pure water will be produced, driving up the flush-to-pure ratio. This chart will show you the effects of changes in temperature and pressure.

Decreasing the incoming pressure also tends to increase that ratio, but not to the same degree.

What is the rated capacity of the system, and what size flow restrictor is on the flush water line? They are typically specified in ml/min.

 

[eggshells]

So is it better to tap it in the hot water rather than cold water?

 

[orcoholic]

I think it would be very expensive to tap into the hot as it would waste a lot of heated water.

 

[eggshells]

yeah I was just looking at the chart. So I guess the best way is the colder the water. Increase water pressure.

 

[keithrs]

Check your water pressure.... Make sure you have the restrictor on the right side going the right way.

Let it run for an hour or more.... I have mine outside and when it's cold out I get very little ro water while I wait for the incoming water to "warm" up my membrane.

 

[Ray]

...and for folks interested in being more conservative, you can always increase the restriction on the outlet of the flush side of the membrane. Yes, it will mean the need to replace membranes more often, but if you pay for your water, and especially if you also pay a sewerage fee based upon water consumption, in a few calculations I've done for folks, it ends up being a significant savings anyway.

FWIW, I've been operating a custom-built 200 gpd system, and at design pressure and temperature, it should be a 1.14:1 ratio. In reality, due to the lower pressure and temperature of my GH water supply and the lower output, I measured the ratio coming out at 2.03:1. In almost 4 months, I see no degradation in the output, so the membrane is apparently not fouling very much.

 

[eggshells]

By often.. Do you mean once a year. It says on mine 2-5 years to replace the membrane.

 

[dodidoki]

PURE Pro M500. cca 1 litre/hour soft water versus 20 litres unusual water. Very disappointing.

 

[Justin]

something is not right. the pure water should be coming out at the volume ratio like Ray said.

 

[keithrs]

It's 50 GPD unit...... That's about 189 L per day. At that rate you should have a very fast drip to slow light stream....

 

[Ray]

By often.. Do you mean once a year. It says on mine 2-5 years to replace the membrane.

The standard recommendation level for a system used at its capacity is:

Sediment filters - 6 months
Carbon prefilters - 12 months
Membranes and (if used) carbon postfilters - 24 months.

I'll admit that those are pretty conservative. As I don't produce at capacity, I run about 2x time periods those in my own system.

 

[NYEric]

For a new unit at worst you should be running 6:1. Also, my unit says used cold water.

 

[dodidoki]

I noticed that if I close the way of wasted water, RO water begins flow faster. I thought about: if I close the way of wasted water, preassure will increase backwards to the tap water side of membrane....so I can adjust the system with appropriate closure of wasted water to optimal running. Is it right?

 

[keithrs]

You don't want to close the waste side off completely..... You can add a smaller restrictor but that won't necessarily give you more production.... Your limited by the membrane flow rate.

I would recommend going to a higher GPD membrane with the appropriate restrictor for the ratio you want.

 

[dodidoki]

You don't want to close the waste side off completely..... You can add a smaller restrictor but that won't necessarily give you more production.... Your limited by the membrane flow rate.

I would recommend going to a higher GPD membrane with the appropriate restrictor for the ratio you want.

No I didn't closed waste side completely, I adjust the system into that level, that RO water outflow is equal to wasted water outflow (1/1 ratio). My system can produce with this adjusment about 3 litres /hous RO water.

 

[eggshells]

How about going 100gpd. What size is your holding tank?

 

[Ray]

What size flow restrictor was provided with the system?

 

[keithrs]

Do you know the TDS of your supply water? I ask because if it's high you'll foul the membrane fairly quickly at 1:1. If you're ok with knowing that then no worries.

 

[NYEric]

Unless you pay for water, my taxes take care of that!, you can run 2:1 or 3:1. Plus if you dont have a lot of plants a couple of gallons on the side should do you for a day.