Reverse osmosis systems and why a home may have one

When looking through looking through listing ads, you might come across a home that features a reverse osmosis or RO system.

Depending on where you've lived, you may not be familiar with this feature. To be sure, it's not something that means there are other issues to be revealed by the home inspection. In fact, RO systems are a benefit to many homeowners. Like a Brita or Pur product, their purpose is to filter impurities from the water in the home. They are more common in properties that use well water, but you might find them in other homes, as well.

How does it work?

RO systems are typically used for filtering lesser amounts of water in a residential property due to their design. In most cases, they are applied to a single tap in a home. There are systems that can filter the water that goes to the entire property, but they are much bigger and more expensive. Additionally, more extensive RO systems can be noticeably loud when they are active.

The process of reverse osmosis is as complex as it sounds, but it can be boiled down to pushing water through a semipermeable membrane. This means that the surface allows some objects through and stops others. Imagine a child-sized door at an arcade. Although parents can try to enter through the door, they are likely too big to fit.

RO systems essentially have the same job. As water reaches the membrane, all particles that are not water molecules are blocked from going any farther. This is because the membrane has tiny holes that only water molecules are small enough to fit through. Although those molecules can get through, the system is still pushing a lot of water through a single membrane at a time, which is why RO systems are typically only used for one tap. Just like a large group of children couldn't get through the kids' door all at once, the water molecules need time pass.

Downsides to using RO for filtration

While RO systems are beneficial and sometimes necessary for having clean water, they have some cons that aren't as appealing.

For instance, not all contaminants are removed. According to resource from the University of Nebraska at Lincoln, there are several contaminants that cannot be excluded via reverse osmosis:

• Some pesticides, solvents and volatile organic chemicals
• Dissolved gases such as hydrogen sulfide

Additionally, the membrane's ability to contain contaminants depends on various factors, including the condition of the membrane, the concentration of the contaminants and chemical properties. The good news is there's a long list of contaminants that can be removed using an RO system:

• Pesticides such as lindane, endrin and pentachlorophenol
• Particles such as cryptosporidium, protozoan cysts and asbestos
• Ions and metals, including arsenic, barium, chloride, lead, sodium and zinc

Do you need an RO system?

Not every home requires this type of filtration system. Most cities have water quality that is suitable for drinking and brushing your teeth. However, if you are looking for a home in an area where many listings have an RO system, you may want to do some homework and discern whether the area you're considering uses well water.

As far as home value is concerned, the system is a significant benefit if the city's water quality isn't good. If there aren't any issues with the water, an RO system could appeal to a few future buyers when you decide to sell the home. Keep in mind, however, that this could be a small group, as some people prefer distilling and carbon filtering to reverse osmosis.