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Who needs a whole house reverse osmosis system and what does it cost?


Whole house reverse osmosis systems are usually used when the water source is really bad. Most municipal sources are not that bad and usually, just filtering, softening (if required) and adding and under sink reverse osmosis system for drinking water is enough to make everybody happy. Where I live the water is very hard and the total dissolved solids is about 600 ppm (parts per million, lake Michigan is 80 ppm, the ocean is about 35,000 ppm). We run a big blue (4.5" x20") filter rated at 20 microns followed by a carbon filter (chlorine makes my wife itch) and an under sink reverse osmosis with a 3 gallon bottle in the kitchen and one in the bedroom that we fill as needed for drinking water. Most of the reverse osmosis water is used for the orchids. If you dechlorinate your water, there will be bacteria growing in your toilets eventually. It is not harmful but you might dump a capful of chlorine in the tank once a month or so to kill the bugs.

To just filter a house and add an under sink reverse osmosis and water bottles should be less than $500.00 (US). The standard reverse osmosis system will remove heavy metals, bacteria, and cysts, the standard problems, down to acceptable levels. Viruses will pass the membrane but so far, in the USA, viruses in the water have not been a health issue and hopefully they never will. If your water source is chlorinated or you have a deep well, pathogens should not be a problem.

People who buy a whole house system are usually on a well and building a new house so the cost can be added to the mortgage. The wells usually have a very high dissolved solids level or other issues that make them undesirable for drinking.

Issues with whole house reverse osmosis systems.

1. Noise - Place them away from the bedroom. After everyone showers in the evening, the system will kick on to fill the tank and the pump will make noise. If you get a 1 gpm system, and you use 120 gallons of water showering, flushing, brushing your teeth, you will have a 2 hour pump run. If you have a teenage daughter like mine, you will have a 4 hr pump run and no hot water for your shower.

2. Cost - You will run 2 pumps, one to feed water to your house when you need it and one high pressure pump to fill the holding tank. If you need a softener, you will have to purchase salt and maintain the softener. You will have to replace the membrane every 3-5 years if it is maintained correctly (more often if you ignore the system).

3. High recovery reverse osmosis systems have a concentrate brine discharge that you will have to deal with. If you have 600 ppm going in and reduce the tds to 10 coming out and get a 50% recovery, the brine will be around 1200 ppm. If it is 66% recovery, you will approach 1800 ppm. This is too high for most irrigation needs and septic system. It is not suitable for stream discharge you you will need a separate leach line for the discharge.

Whole house reverse osmosis systems costs vary with the water quality and your needs. Get a water analysis first!

1. The basic system consists of controls, membrane and housing, high pressure pump and motor, 2 pressure gauges, 3 control valves, 3 flow meters, low pressure switch, conductivity monitor, and mounting skid. We build the high pressure system out of stainless so we never have to worry about leaks or service problems.

2. A whole house reverse osmosis system will have flows lower than the flow rate to the house so you will need a holding tank, pump and bladder (pressure) tank to feed the water to the house.

3. If the water has high calcium or you want to recover a major portion of the well water, you may need to remove the calcium/magnesium (hardness) with a softener. You may also use a polymer or acid feed to minimize hardness problems in the system. Usually, with high hardness, a polymer addition system is much less expensive to run than a softener but it takes more attention than a softener.

4. If you live in an area where there has been volcanic activity, the silica may be high in the water and that may limit the recovery rates. Don't plan on an 80% water recovery rate.

Costs -
1. Reverse Osmosis mounted on skid with recycle loop, prefilter, all kinds of neat stuff to make it work. Approximately 6,000. USD for 1 gpm. Set up to interface to following items.

2. Water storage and repressurization system with pump and bladder tank mounted on RO skid. Includes integrated level control for reverse osmosis system. Costs run $2000-4000 depending on tank size, pressure required and flow rate.

3. Water softener if required. Sized to regenerate after set flow volume. Integrated to RO controller to prevent hardness bypass during regeneration. Available as dual system. Cost base on water analysis, usually runs $800-3000 depending on water quality.

4. Polymer addition system to sequester calcium. Used instead of softener. Costs about $000-1200 per unit.

5. Installation - plumbing and electrical. Depends on local rates but it should run $300-400 total.