REVERSE OSMOSIS WHOLE HOUSE

We custom build whole house reverse osmosis systems. We are experienced professionals. 

First, read this article. Then bring us some water from your well and bring photos of any equipment you have. We will work with you to design and build a treatment system that your family can rely on for years to come. 

This article addresses reverse osmosis for rural, single family residential use, where a supply of fresh water is unavailable, and the well produces saltwater.

Purpose

Reverse osmosis, or RO, is the most effective process to remove salt from water. It is used worldwide in water utility installations, mobile military water plants, commercial, industrial, and residential uses. A well designed and properly maintained RO can remove more than 90% of salt, many other contaminants, providing fresh, high quality drinking water. 

Definition

Dictionary.com defines osmosis as follows.

“osmosis

a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane”

Osmosis is the method by which cells control the flow of water and minerals. 

Reverse osmosis is the mechanical application of applying high pressure salt water against an artificial membrane to force the water molecules through the membrane, leaving the salt behind, in a highly concentrated stream of wastewater. 

Dictionary.com defines reverse osmosis as follows,

“reverse osmosis

a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.”

The need for Reverse Osmosis: 

Saltwater can make a property uninhabitable. Depending on the concentration, it can be destructively corrosive to the steel parts of the well, the pump, the plumbing, appliances, and any metal object. It can be unpleasant or even impossible to use in the home. A well designed and properly maintained RO can remove more than 90% of salt, many other contaminants, providing fresh, high quality drinking water. 

It is best to take a sample of the source water to an EPA certified water laboratory and have the water analyzed for Chlorides and Total Dissolved Solids (TDS). The information is needed to select the proper treatment equipment. Other water analyses may be required. We recommend using a qualified laboratory for the initial analyses because accurate information is critical to proper planning. 

Reverse osmosis process

In a typical residential application with a private well containing saltwater the well pump moves the source water to the pressure tank, then to the pretreatment filter that removes hydrogen sulfide gas and small amounts of iron from the water before the water goes to the RO machine. 

The reverse osmosis machine produces water at a slow rate, about 1 to 3 gallons per minute. A large storage tank, usually 500 to 1,000 gallons is required. People use water quickly and the machine refills it slowly. 

The reverse osmosis, or RO, splits the water into two streams. There is a permeate stream of water which is the fresh water. The other stream of water is called concentrate. This water is very salty. The concentrate water flows outdoors to a disposal area. The permeate water flows into the storage tank. The RO water may be low in pH at this point, which may cause corrosion problems in the home. It may require a calcite feeder to increase the pH of the water so that it is neutral and non-corrosive. The water in the storage tank is not the finished product. Liquid chlorine solution is added to the water in the storage tank with a metering pump to disinfect the water and to remove any remaining sulfur odors. The water then flows through a carbon filter to remove the chlorine, and then to the house. The water in the storage tank is not pressurized. A pump and pressure tank system is required to move the water to the home.

Operation Daily use of the water system is like daily use with utility water, except for a few considerations. The water system is designed for normal household use, but it has capacity limits. If the user exceeds the limits, the water will stop flowing until the system has time to refill the storage tanks. Oversights that may be tolerable with a utility water supply must be avoided when using an RO system. Leaks of any kind, no matter how small, must be corrected immediately. Use of water hoses outside must be limited and turned off when not needed. The system is not intended for sprinklers or irrigation. You will run out of water! Do not allow a hose to flow uncontrolled. Toilets must be strictly maintained to avoid loss of water due to a defective flapper or a water flowing down the overflow tube. Topping off a swimming pool must be closely monitored. 

Here is the math. If the storage tank contains 1,000 gallons of water, and the RO refills it a rate of 2 gallons per minute, and someone leaves a hose running outside at 6 gallons per minute, you have a 4 gallon per minute deficit. You are losing water at a rate of 240 gallons per hour. (4 x 60) You will be out of water in 4 hours. Maybe it ran all night at the chicken coop! You discover you have no water and turn off the hose. The RO will take 8 hours and 20 minutes to refill your storage tank.

(1,000 gallons / 2gallons per minute = 500 minutes) (500 minutes / 60 minutes per hour = 8.3 hours)

Life span: The system should be designed for a twenty-year life expectancy with recommended maintenance. Choose a supplier that can provide service for the life of the system. 

Capacity: Industry data indicates a per capita water consumption rate of 75 gallons per person per day. A family of four will consume, on average, 300 gallons per day. 

Pressure: The pressure of water delivered to the home must be at least 20 pounds per square inch (PSI) as per industry standards. Most consumers are accustomed to 30 to 50 PSI. 

Flow rate: Most homes require a peak flow rate of 8 gallons per minute. 

The Building:  We recommend a building with a concrete slab floor at least 6 feet wide and 8 feet long and 4 inches thick, and one or two floor drains because water will be spilled. The building should have a strong roof, 8 feet high inside. The building should be well lighted. Extra electrical receptacles are needed to power tools. Large doors are recommended because access is required to every piece of equipment for service. Some units will need to be removed. 

Location: The building should be located so that it is close the water source, electricity source, the residence, and is accessible by service vehicles. The well should be accessible by well service trucks. Overhead obstructions should be eliminated so that a 30 feet tall pump hoist truck can remove the submersible pump someday. 

Ventilation is absolutely necessary. There will be corrosive fumes from hydrogen sulfide gas emanating from the water, and liquid chlorine. These fumes are heavier than air and will settle near the floor. Hydrogen sulfide gas combined with condensation on the metal parts, and electric motors will result in destructive corrosion and system failure. An exhaust fan in a wall near the floor works best when used in a cross ventilated building to keep the air moving. 

Electrical requirements: CAUTION! Consult with a licensed electrician for any electrical work. Improper electrical work may result in property damage, injury, or death! 

GFCI receptacles in a wet environment are critical for personal safety and protecting the system. 

The well is likely to be a 230-volt circuit with a dedicated circuit breaker. It cannot be used to power other treatment equipment. The RO machine will need its own dedicated power supply. Most units will operate on 115 or 230 volts powered by a 20-amp circuit breaker. The 230-volt circuit will be more efficient with the cost of electricity. The secondary water pump that delivers water to the house will also need its own circuit breaker and power supply. It is better to power this pump with 115 volts on a 20-amp circuit breaker. This is because if you are operating on a generator during a power outage, and if the generator only has 115-volt power, stored water can still be supplied to the home. The average RO water treatment system will operate satisfactorily on a 60-amp subpanel. The chlorine pump, the automatic backwash filers and other devices require 115 volt GFCI protected receptacles on their own 20 amp circuit breakers. 

Scheduled Maintenance: Scheduled maintenance can be relatively simple. The RO machine requires a filter to be replaced monthly. The purpose of the filter is to protect the pump. Liquid chlorine, the same type sold in pool stores, must be added monthly to a solution barrel for disinfection. There are water tests to perform, gauges to read and adjustments to make. It is important to be observant and keep records. 

Cost of ownership: An RO system is expensive to purchase. Proper planning is essential to make an informed decision. It is an investment to be protected with diligent maintenance and care. The electrical cost will be higher than operating a standard well water treatment system. Where a well has one electric motor, usually one horsepower (746) watts and it may run an hour or two per day, and RO system adds 2 electric motors. This gives a total of three electric motors, two of which will operate three to four times the normal amount of time as a one motor system. This is because of the way an RO machine processes water. The waste stream is three to four times the amount of volume as the permeate, or fresh water stream. For every 1,000 gallons of water pumped by the well and processed by the RO machine, about 250 to 330 gallons is available to the home. It is wise to conserve water wherever it is possible. RO water should not be used for irrigation or other high consumption activities.

A well and a water system are like a roof or an HVAC system in that repairs and replacement costs are inevitable, significant, and must be budgeted. 

Resiliency:

Power outages: A storm event, a power outage and other disruptions are inevitable and must be considered when planning. The most likely disruption is a power outage. Some power outages in our area have lasted up to two weeks. Stored water is a critical asset. Experience has shown us that a family of four can make 1,000 gallons of water last one week with careful conservation. The more storage one can get, the better chance of not running out of water. 

A standby generator capable of operating the entire water system would be an ideal way to keep the water on during a power outage. It would only need to run long enough to provide water.  An alternative would plan would be to operate just the delivery pump to supply water from the storage tank to the house. This pump would be 115 volt, ¾ horsepower (560 watts running, 840 watts starting), which would require a 1kw sized generator. The RO system would replenish the storage tank when the power is restored. 

Flooding: If flooding is a possibility, it is best to construct all electrical receptacles and components above the expected high-water line. Electric motors and RO machines should be mounted on pedestals above the high-water line. Spigots, filter drains and other fittings that could allow floodwater to enter the water system should be elevated. Flood water is not usually damaging to plastic or fiberglass water tanks, although an empty tank may float and cause damage. 

Wind Damage: Hurricanes are inevitable. Construct the building or shelter to withstand high winds and to protect the system from damage from wind-driven debris such as tree branches.

Changes in source water: Source water quality and volume may change. It may produce contaminants that were not present when the treatment system was constructed. Upgrades to the treatment system may be necessary. The source may yield less water than it did when first placed into service. Water wells wear out and must be replaced. turn saltwater ointo fresh water

This schematic is for informational purposes only. It does not represent any particular treatment system. 

1- Source water well pump

2-Pressure tank

3-Pre-treatment filter

4-Reverse Osmosis machine

5-Storage tank

6-Chlorine solution barrel and metering pump

7-Post-treatment filter

8-Pressure tank

9-Delivery pump

The average floor space required is 6 feet x 8 feet.