What is whole house reverse osmosis?

Whole House RO Checklist

A whole house reverse osmosis (RO) system filters all water entering your house. This includes bathroom, kitchen and even laundry. A proper whole house RO design starts from a comprehensive water quality test that specifies the contaminant concentrations of microbiologicals, metals, physical factors, inorganics and organics in your water. Next we decide what type of pretreatment is needed before water is properly conditioned to enter a RO system. Too much iron, silica, manganese, chlorine, hardness or low pH can damage a RO system. After filtering through a RO, the water is stored in a pressure tank (only low water use) or an atmospheric tank and disinfected to prevent microbial growth. At the next step, water pressure is raised with the help of a booster pump. Finally, post treatment fine-tunes any tastes, corrosion control issues and pH adjustment.

Whole House Reverse Osmosis Illustration

Do I need whole house reverse osmosis?

City Water

If you’re on municipal water (US), whole house reverse osmosis is almost always over kill. City water is already treated to comply with Environment Protection Agancy (EPA) standards.  You don’t need to have a complete water treatment plant at home. Instead, you’re better off with a smaller undersink type RO system, just for drinking water and a whole house catalytic carbon backwash filter for chlorine/chloramine reduction plus a water softener for water hardness treatment.

Well Water

If you’re on well water, obtaining an informational water quality report is a critical step to ensure that the water treatment is efficient and cost effective to deal with your water issues. Nevertheless, most water issues can be fixed by single treatment or a combination of water treatment technologies such as particulate filtration, aeration, ion exchange, oxidizing agent (chlorine, ozone, peroxide or potassium permanganate), oxidation and/or uv disinfection. Whole House RO should only be attempted when you have multiple challenging water problems such as elevated levels of nitrate, chromium, brackish water tds, arsenic…etc. Test the water through a laboratory certified for drinking water analysis and email us the water report to sales@wecofilters.com.

Sample Water Analysis from National Laboratories


How big should the RO be?

According to EPA, the average American family uses more than 300 gallons of water per day at home. We take a good look at the water temperature, TDS, pH, silica & hardness before determining the size of the RO you need. Since RO membranes lose around 2% of water production for every degree below 77 °F, we sometimes recommend purchasing an RO that is 3 or 4 times the capacity you need.

What are the features of the RO?

Pre-filters - Sediment filter captures particulate matter in water.

                 - Carbon filter reduces organics, chlorine in water.

Booster Pump - Increases water pressure before feeding the reverse osmosis membrane. Typical residential RO membranes are rated at 65 psi. Commercial ultra low pressure membranes such as the AXEON HF5 series used in our ULE systems operate at 80 psi feed pressure. Most other commercial grade membranes operate at 150 - 225 psi pressure.

Low pressure switch - Shuts off the pump when pre-filters are clogged or when water supply does not have enough water to run the system.

Membrane - Removes most of the contaminants in water.

Concentrate Valve - Regulates the amount of waste water sent down the drain. Also used to flush the membrane periodically. 

Recycle Valve - Recirculates a portion of the waste water.

Dual TDS Meter - Measures the feed and permeate (filtered) water streams for the total dissolved solids concentration.

What else do I need?

Depending on the water hardness, iron content, pH, silica and other contaminants listed on your water analysis, you may need additional treatment equiment to go upstream and/or downstream the main RO filter system. 


Membrane is the most delicate part of any RO system. While the performance of the membrane is mostly dependant upon the TDS of feed water, pressure and water temperature, the longevity of the membrane is impacted by feed water hardness, iron, manganese, suspended solids, pH, silica, chlorine & chloramine, organics and bacteria. Water must be pre-treated so that all these are below the thresolds recommended by the RO manufacturer.

Treated water storage

For a very low volume of water (up to around 80 gal - one person house) a simple pressure tank would suffice. However, households run into peak times where showers and multiple faucets are open at the same time. This will exhaust the capacity of a pressure tank very quickly and you will be out of water. Atmospheric tanks can hold a larger amount of water. We carry 100, 300, 500 and even 1000 gal atmospheric water tanks in stock. Water from atmospheric tanks need to be re-pressurized before household use. We prefer having an atmospheric storage tank with a capacity of 4 days of water storage.

Pressure Pump

Water stored in an atmospheric tanks do not hold any pressure. A pressure pump delivers water out of the holding tank and distribute is throughout the house. Constant pressure pumps sense water use at house and increases/decreases pressure.


Reverse Osmosis typically reduces pH by 1 whole pH unit. If your house plumbing is copper, this can lead to corrosion isues. A calcite or magnesium oxide filter will neutralize the water before distribution to the house.

Where do I install?

Atmospheric tanks are quite large and require considerable storage space. RO systems in operation can be loud, specially ones with carbonator pumps. Locate the equipment that has a floor drain to handle leaks or spillage during service or maintenance. Comply with all state and local plumbing codes. Install vacuum breakers at backwash filter/softener drains. Waste line should be able to handle at least twice the household water usage if using a 1:1 RO system.

Chat with us and let us know if you have any other questions about whole house reverse osmosis.