All of our units are supplied with Stainless Steel high pressure pumps, automatic shut off valves for low pressure, full water tanks and unacceptable product TDS level. Exstar recommends installation by an experienced electrical and plumbing technician. However, boat owners with sufficient experience are capable with the detailed drawings and instructions found in our manuals.
Other Frequently Asked Questions:
- What “size” unit should I have – how many gallons per day (GPD)?
- How do I clean (backflush) the system?
- Can I use the unit in brackish water?
- How much time before fresh water is available?
- What is required for installation?
- How often should I clean the membranes? What is their life expectation?
- How long do the pre-filters last? (5&30 micron filters)
- What are Total Dissolved Solids (TDS)?
- What should the TDS be for my drinking water?
- How does “Percent Recovery” relate to the membranes?
1. What “size” unit should I have – how many gallons per day (GPD)?
If a unit is rated at 400 (GPD) – remember that is based on it running
continuously for 24 hours. This is rarely the case. Typically RO’s operate for
part of a day. To find the volume you will actually use per day:
divide your total gallon usage by the amount of hours the RO will run,
this will give you – Gallons per Hour required.
example – 200 gallons divided by 5 hours = 40 gallons per hour
multiply this X 24 hrs = 960 Gallon per Day(GPD) system is required*.
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2. How do I clean (backflush) the system?
The XP and SW RO’s have a manual FWF (fresh water flush) system built in.The FWF should be performed once per week. This protects and extends the life of the membranes. The membranes’ condition are key to the reverse osmosis process. The FWF is also available automated as an option. NOTE: there is additional information in MEMBRANE FAQ’s
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3. Can I use the unit in brackish water?
Sweetwater units operate in brackish water. It actually takes less pressure and power to run brackish water through the RO process, than it does with saltwater. When running in rivers, harbors and other brackish water areas –
Exstar’s Oil/water separator cartridges are REQUIRED to protect your membranes. UV sterilizers are another option recommended for the product water when running in harbors.
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4. How much time before fresh water is available?
In less than 5 minute after startup.
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5. What is required for installation?
You will need a thru-hull inlet(1/2”-1”), a sea cock valve, over board thru-hull discharge fitting, a product water tank and electrical circuit breaker. The system can be located above the water line, but the feedwater pump/booster pump should be below the water line.
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6. How often should I clean the membranes? What is their life expectation?
RO membranes should be cleaned as needed. You can usually tell it’s time when the product water volume rate drops off. Also, check your TDS meter to monitor the membrane efficiency. Increased TDS readings indicate a need for membrane cleaning or replacement. Membranes last an average of 2-3 years.
They can go as long as 5 years before replacement. The fresh water flush prolongs membrane and pre-filter life.
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7. How long do the pre-filters last? (5&30 micron filters)
You should change these filters once every 6-8 months. It’s time when you notice the holding tank not filling up as quickly by the system slowing down significantly.
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8. What are Total Dissolved Solids (TDS)?
It is the total weight of all solids dissolved in a given volume of water. Usually expressed in mg/L (milligrams per litre) or referred to as ppm (parts per million) These dissolved solids refer to any minerals, salts, metals, cations (positively charged ions ) and anions (negatively charged ions) in the water.
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9. What should the TDS be for my drinking water?
Sea saltwater averages a TDS of appx 36,500. Exstar saltwater marine membranes reduce the TDS to 250 or below (99%+) reduction. Bottled water standards require a TDS of <250 in order to call the product “mineral water”.
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10. How does “Percent Recovery” relate to the membranes?
The percent recovery at which a membrane is operated will affect the quality and quantity of the product water. As recovery rates increase so does the TDS
of the brine(waste). High recovery rates may be attractive, but there are limitations set by membrane manufacturers.
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TERMS
mg/L – An abbreviation for milligrams per liter of measurement to express
concentration of contaminants. Used interchangeably with ppm.
NTU – Nephelometric turbidity unit, an arbitrary unit measuring the turbidity
in water by the light scattering effect of small suspended particles in a light beam.
Permeate - The water that has passed through the membrane stage of treatment.
Product water - The water produced by the reverse osmosis treatment process.
% Recovery – Percentage of feed water that is reclaimed as permeate.
% Rejection – The percentage of the feedwater TDS that is prevented from
passing through the membrane with the permeate.
Feed pump – Pump which supplies water from the source to the RO unit.
Fresh Water Flush (FWF) – Cleaning the membranes, pumps, plumbing and system by back flushing the unit with fresh water. A very important maintenance operation improving membrane life.
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