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Road Map to RVing => Full-time RVing => Filtering Water



water Filtering Water Part 1

To stay in good health on the road, it is essential that the water you drink is free of bacteria, virus, and dangerous chemicals. One of the first things to add to your RV is a water filtering system. There are several options available.

For water filters to be effective and not add to health problems, they must be in use all the time. If you store the RV for more than a couple of months, remove all water filters and discard (see  Bacteriostatic Filters below).

If boondocking for long periods of time without being hooked up to city water, the minimum solution for clean water would be to install an inline filter under the sink, then use another filter that hooks up to the water hose when filling up the fresh water tank.

water filter

There are new filter materials on the market that you may want to explore if you are a seasonal traveler or boondock frequently.

For an expert's opinion on water filters and related issues, I visited Rick at the RVWaterFilterStore.com.

New Bacteriostatic Filters

KDF is an alloy containing zinc and copper that can be incorporated into carbon filters to make them bacteriostatic. That means that bacteria cannot grow inside the filter. This is particularly good for people who use their RV intermittently, as KDF will protect the filter while the RV is not being used.

There are several other chemicals that manufacturers use to make their filters bacteriostatic, but many of them affect you as well as the bacteria!  KDF has a very good record as being the safest agent yet found for keeping bacteria from growing in filters, although silver nitrate is common, also.

Reverse Osmosis (RO) Systems

If you primarily stay in RV parks hooked up to utilities, a Reverse Osmosis system may be the best alternative. This system costs about $250, easy to install, and provides the cleanest water you can easily filter on the road. A two-gallon holding tank is all you need, and it can be tucked under the sink or dinette.

The system shown here is the one I use. It has two pre-filters, an RO membrane, a small carbon filter on top to handle any smell from the holding tank, a tall faucet, and a two-gallon stainless holding tank.

Water pressure from the RV park must be at least 40 psi to start the RO process. The higher the water pressure, the better the filter results, less TDS in the water. The system filters the water until the two-gallon tank is full, then switches off until needed again.

Install the long-necked faucet included with the system for drinking water. The shape makes filling jugs and water bottles easy and quick.

RO system

I also have two pre-filters (1 is carbon) installed in an outside cabinet where my water hookups are located. They can also be on the ground (some RVers use a bucket or a special spiked retainer sold at most RV supply stores).


This provides a simple "whole RV " filter system that lowers the TDS for the shower, washer, and dish washing water. Use the 5 Micron-size filters.

Since I travel primarily in the sun belt where the TDS reads high, around 450-600, this helps keep the shower water softer without using a salt-based product.

In order to evaluate the water quality, a small TDS meter is inexpensive and available. The one I use is pretty reliable.

Water Tester

From Rick at the RVWaterFilterStore.com:

RO system recommendations to reduce total dissolved solids (TDS) from the water source:

Formula for Determining When to Replace Filters

Divide the RO water reading by the source water, and subtract that from 100 to determine the water rejection (%) rate.

Water rejection rate: Rejection is the RO term for the percentage of the minerals (or TDS) the RO membrane is removing (rejecting). So this rejection percentage is the amount of water going down the drain or back into the freshwater tank if you have the boondocker option, taking the rejected minerals with it.

Example: 170 (current meter reading of RO water) divided by 600 (current meter reading of non-RO (source) water) = .28 (drop the decimal). Subtract 28 from 100 = 72, meaning you have a 72% TDS rejection rate. The RO unit is removing all but 28 % of the TDS from the water. I like to see a TDS meter reading of 50 (or 92% rejection rate which means all but 8% of TDS is filtered out).

Based on this formula, if your membrane was in really good shape (1 year old or less), you might expect to have about a 15-30 TDS reading if the water supply is in the 200-350 ppm range. As it ages, it wears open to the point of which it can get down to about 75-80% removal of TDS. That is the suggested time to remove and replace the membrane

75% rejection rate is the standard alert to change the filters.

You can go further, if you wish, but it will be continuing to leave more minerals in and that may not be satisfactory for most people.

Now, all that being said, by government standards, anything less than 500 ppm is considered fine.

More About Filters - Part 2

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