Does Hot Water Ruin Water Filters? Sometimes!

I have had customers ask me if I could run hot water through their reverse osmosis drinking water system so they could have filtered hot water whenever they wanted to make hot tea or coffee.

Although this may sound like a great idea, the quality of the water that your reverse osmosis would produce would not be what you might expect, and here’s why.

Does Hot Water Ruin Water Filters? Many water filters including reverse osmosis membranes are made of woven polypropylene or polyester. Exposing polypropylene or polyester water filters to hot water can cause the weave to loosen, reducing the effectiveness of the filter. Wound natural string or cellulose filters are less affected by hot water.

If you have exposed your water filters to hot water, that doesn’t necessarily mean that they are now useless. Most of the time, homes hot water is not hot enough to damage a water filter unless it is exposed to it for a long period of time.

How can you tell if your water filter has been ruined by hot water?

Sometimes you can’t tell right away if your water filter has been damaged due to hot water. A sediment filter that is brand new may still filter out most of the sediment in your water even if it has been damaged from hot water, it just may not last as long.

If you have damaged a reverse osmosis membrane by exposing it to hot water, you may not taste any difference in the water for several days since the system stores several gallons of filtered water in its storage tank.

To get an idea of just how much stored reverse osmosis water you have, see my article How Much Water Does An RO Tank Hold? (Approximately).

Even after a few days, you may not notice that your reverse osmosis membrane has been ruined if you only use your reverse osmosis water for coffee, tea, or drink mixes. See Are Water Filters Necessary For Coffee Makers?

The only safe way to check that your reverse osmosis membrane is working correctly is by testing the reverse osmosis water and comparing it to the unfiltered tap water with a TDS meter.

A TDS meter measures the Total Dissolved Solids in a given sample of water.

The water produced by a reverse osmosis drinking water system should have a TDS reading of about 5% of the TDS reading of the water before going through the system.

As a reverse osmosis membrane gets older, the TDS may rise above 5% which is fine. I generally replace a reverse osmosis membrane once the TDS rises above 10%.

You can get this easy to use TDS meter to check your reverse osmosis water and tap water.

How hot does water have to be to ruin a water filter?

Water would have to be very hot in order to ruin a standard water filter. Most residential water heaters are set to a much lower temperature than would do any damage to a water filter unless it was exposed for a long period of time.

But many homes have their water temperature set higher than average. Water temperatures above 140 degrees may cause damage to a water filter if exposed for more than just a few seconds. But a reverse osmosis membrane is a very different story.

Reverse osmosis membranes are very fragile and delicate. Not only can their ability to filter out unwanted solids from your water be affected by hot water, but even very warm water can cause them not to get damaged, and therefore not filter properly.

A reverse osmosis membrane should not be exposed to water above 95 degrees Fahrenheit. Even short term exposure to this temperature can cause damage to the membrane.

Does hot water ruin a Brita carbon filter?

Running hot water through a Brita carbon filter will not affect the ability of the carbon to remove contaminants from the water. But excessively hot water of 200 degrees or above could affect the housing that contains the carbon.

Brita carbon filters are intended for use in hot or cold water, and their filtering ability will not be affected by average household water temperature. Source