[Buckeye Field Supply]

You may have noticed your RO or RO/DI system produces less purified water during the winter when tap water temperatures decline. Feed water temperature, and feed water pressure (usually expressed in pounds per square inch, or psi) are the two variables that most affect this production. The concentration of impurities in the feed water also affects production.

FILMTEC® rates the production from their 50, 75, and 100 gallons per day (gpd) membranes (± 20 %) under controlled conditions, with 250 ppm TDS softened feed water at 77 degrees Fahrenheit and 50 psi, with 15% recovery (or about a 5:1 waste to permeate ratio).

Colder water, water under less pressure, or harder water (higher TDS) will reduce the amount of water purified by the membrane. Because reef hobbyists typically don’t have means to modify the amount of dissolved solids in feed water, discussion of system production often focuses on the variables we can control: temperature and pressure. There are various means to modify feed water temperature, and feed water pressure can be enhanced with a booster pump.

To answer the question “How much permeate should my system be producing?” Buckeye Field Supply announces the availability of a new calculator to estimate the production of purified water from systems utilizing 50, 75, and 100 gallon per day (gpd) Filmtec reverse osmosis membranes. The calculator allows input for water temperature in Celsius or Fahrenheit, and water pressure in psi (with an assumed feed water dissolved solids concentration of 250 ppm), and provides an estimate of the expected production of purified water expressed in gpd. If the production from your system is substantially lower than values produced by the calculator, the membrane may need to be replaced.

To maximize your control and facilitate use of the calculator, Buckeye Field Supply Premium Series and Reef/Residential Series system include a pressure gauge and liquid crystal thermometer. These combined features are available nowhere else in the point-of-use RO/DI market.

Russ @ BFS

[Reefland]

Russ,

I am curious, if the saddle valves are commonly used by aquarists, and they only work on cold water lines, what are we to do to get the best production from our unit?

[Buckeye Field Supply]

Originally Posted by Reefland

Russ,

I am curious, if the saddle valves are commonly used by aquarists, and they only work on cold water lines, what are we to do to get the best production from our unit?

It is true that almost all RO systems used in this hobby use feed water from a cold water pipe (self-piercing needle vales are not the best way to do this, but they are used).

As you are aware, that water is often below 77 degrees F. This is one of the reasons that you may hear us advise that its unlikely you'll get (for example), 75 gpd from a 75 gpd membrane. One thing you can do is buy a membrane with this in mind - if you think you'd like a 50 gpd, get a 75 gpd membrane.

You can also boost pressure to compensate for low temperature. You can do this with an adjustable flow restrictor (cheap, but requires you understand what you're adjusting and why), or better yet, with a booster pump. There are a number of DIY designs to boost the feed water temperature as well.

Russ @ BFS

[Reefland]

Russ,

It sounds like the best option is to find a way to get hot water through the system then. Would using one of the hard plumbed valves like a refridgerator uses work ok? Is using straight hot water a bad thing for the unit or membrane?

[Buckeye Field Supply]

Hot water will damage the membrane. Warm water, if kept under about 85 degree F would be great. The trouble is that when people set up DIY systems to mix hot and cold water, too often mistakes cause straight hot water to be delivered to the membrane. Mixing valves are available but are really too expensive for this application.

Self-piercing neees are ok, but other connection options should be explored first.

Russ

[Reefland]

Well, so cold water is no good, nor is hot water. Guess I should install a sink and just use the faucet adapter to control the temp better...

[Buckeye Field Supply]

Originally Posted by Reefland

Well, so cold water is no good, nor is hot water. Guess I should install a sink and just use the faucet adapter to control the temp better...

Sorry there's not a easy solution to this one.

Your suggestions is one of the techniques that gets people into trouble - when the temp of the water coming out of the faucet changes without any change in the position of the faucet handle (when the sprinkler cames on and someone flushes a toilet - placing extra demand on the cold water for instance). If you go this route, leave yourself a healthy margin of error. Adjust your faucet to 70 for instance, to make sure you avoid doses of hot water to the membrane.

The typical way to deal with cold water is to understand the demand, understand the effect of temperature and pressure on production, and select the membrane capacity you buy accordingly.

Russ