Can you use a reverse osmosis filters and tankless heaters together?

Depending on where you live, you might have a less than ideal source of water. If you have poor water quality where you live, you might turn to a system like a countertop water filtration system or a reverse osmosis filter system to provide clean and pure water to your whole house.

You may ask yourself, does it make sense to use RO water in your tankless water heater?

Impact of Reverse Osmosis

A few things to consider with reverse osmosis – first of all it lowers the pH value of the water. This will impact the taste of the water, but not how it will interact with the tankless water heater. The most important factor is that reverse osmosis removes up to 99% of all the sediments in your water, with the innovative membrane the filter uses.

That means the most dreaded part of owning a tankless water heater — performing annual maintenance — will virtually be gone if the water has been treated with reverse osmosis. The majority of the maintenance required with a tankless water heater is because the water has too much sediment which builds up around the heat exchanger, such as calcium and limescale. However, these sediments will be filtered out by the reverse osmosis membrane and never actually make it into the tankless water heater. Therefore, you will have to do significantly less, if not any, maintenance on your tankless water heater.

Water waste – don’t let it in your system!

The one problem you may run into is that reverse osmosis, as it currently stands, tends to waste water in order to filter it. This is because a significant amount of water is required to flush all that sediment out of the RO membrane. That means you might need a more advanced setup to ensure that the flush water doesn’t get into the tankless water heater; which could cause significant damage.

Installation – don’t do it yourself!

Make sure you contact a local plumbing professional to install an RO / Tankless water heater setup. Because you are either working with live electricity lines, or even more dangerous, natural gas lines, you should definitely be working with a certified professional. We do not recommend a do it yourself (DIY) approach to tankless water heating, it can be quite dangerous, and expensive if you make a mistake. It’s worth noting that most of the brands will void the warranty if you cannot prove that it was installed by a certified professional in your area.

Bottom Line – it can be done

Yes, you can use an RO system together with a tankless water heater and expect that you will have significantly less maintenance to perform on your heating unit. That said, be prepared for increased water costs, as the RO membrane will require significant amounts of water to flush out all the sediments that aren’t making their way into your tankless water heater.