5 Reasons Well Water Is Not Good For Washing Cars


If you’re planning on washing your car with well water, you may be wondering if it can be harmful or not. The last thing you need is to damage the car paint, body work or trims. It’s important to know what’s in well water and the signs it may be causing your car damage.

Well water can contain high levels of minerals, iron, sediment, chemicals or solvents and should be avoided when washing your car. Signs well water may be causing damage include mineral deposits, streaks and pits on the car paint, trims or metal work.

Some contaminants found in well water can be harmful to your car. In this post I’ll go into detail on what signs to look out for and I’ll also give you some tips on how you CAN clean your car using well water – so you don’t cause any long-term damage.

Why well water is not good for washing cars?

Around 15% of the U.S. use well water and depending on where you live, well water can contain varying levels of contaminants. Some well water is relatively clean and almost drinkable without doing much to it. Other areas of the U.S. have well water that you wouldn’t even give to your least favorite plant, let along put it on your car, and certainly requires a high level of purification before use.

The 5 biggest concerns with washing your car (or boat) with well water are:

  • Hard water
  • Iron
  • Total dissolved solids (TDS)
  • Total suspended solids (TSS)
  • Chemicals and solvents

Here’s more detail on each:

1. Hard water

Hard water means it has a high mineral content – mainly calcium and magnesium.

  • Hard water is classified as having a mineral content of 121-180 mg/L.
  • Very hard water is anything greater than 180 mg/L.

HARD water can be corrosive!

The main issues associated with washing your car with hard water are:

  • Mineral residue
  • Corrosion
  • Inadequate cleaning
  • Increased soap consumption
  • Low soap foaming qualities

Hard water mineral residue and corrosion

Hard water can give your car a dull luster and coat your windshield making it opaque. However, this can be easily fixed with the right car cleaning products – or a lot of elbow grease!

Over time, these hard water minerals can react with the car paint and metal work. In the beginning they usually just look like chalky-white water spots, but eventually these can form pits.

It’s always a good idea to remove any excess water as you go. Wash a small section, rinse it off and then wipe it down until completely dry. This way you avoid letting any minerals precipitate out of the water droplets as would happen if you let it dry by itself.

If you do end up with a mineral residue on your windshield, side mirrors or windows it can be easily removed using a tough scale residue remover such as Bio-Clean hard water spot remover or Eraser water spot remover which are conveniently available on Amazon.

If you are washing your car with well water, it’s best to give it a final rinse with RO or distilled water. Reverse osmosis systems don’t remove ALL dissolved minerals in well water, but they do remove most of it. If you’re worried, distilled water is best as it will not contain any minerals.

Hard water and soap

Hard water basically counteracts soap and its ability to remove dirt and grime from your car.

Under normal circumstances, soap molecules take up dirt and grease by surrounding them and carrying them away with the water. Unfortunately, when the water is hard there is an abundance of calcium and magnesium and soap preferentially takes up these minerals instead of the dirt or grease.

This means when the water is hard, soap does not tend to work very well. And cleaning your car can be very difficult!

Many people find they have to use A LOT more soap to adequately clean their car or to achieve some level of foaminess.

2. Iron

Iron forms iron oxide when combined with oxygen – aka RUST.

You can’t see dissolved iron in water, but once exposed to air the water can sometimes take on a reddish/orange tinge. If you ever see a red or orange stain on your car, your water likely has a high iron content.

You must be careful if you have high iron in your well water, as it can eat away at the paint and metal body of your car.

3. Total Dissolved Solids (TDS)

Total dissolved solids in well water typically include:

  • Sodium bicarbonate
  • Sulfates
  • Chlorides
  • Potassium
  • Inorganic matter
  • Calcium and magnesium (hard water minerals)
  • Ferrous iron (aka dissolved iron or Fe2+)

For drinking water, TDS is considered safe by the EPA up to 500 PPM (parts per million).

This may surprise you, but for car washing the TDS range should be between 0-50 PPM for a spot-free finish.

So, just because the water is safe to drink does not mean that it’s ok for washing your car!­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

Water spots are only visible on your car because of the impurities left behind from the water. Pure water, especially distilled water, do not leave spots.

Over time, water spots can become permanent as they can etch into the clear coat on your car, which reduces:

  • UV protection
  • Depth and Gloss of the color coat.
  • Protection from other chemicals

4. Total Suspended Solids (TSS)

Total suspended solids are inorganic or organic particulates that are capable of being suspended or carried by the water but are not dissolved in it. These typically include:

  • Chunks of scale
  • Ferric iron (aka insoluble iron or Fe3+)
  • Sand, silt, and clays

The biggest problem with washing your car with water that has high TSS is the particles act like sandpaper. This can quickly and easily damage the paint, windows, windshield and trims on your car.

An easy fix for high TSS is to use a garden hose sediment filter.

5. Chemicals and solvents

Well water can contain various chemicals or solvents that can react with the car paint and can sometimes cause permanent damage. They can also react with the car trims.

Some of these include:

  • Trihalomethanes (TTHMs) – found as a solvent or refrigerant
  • Trichloroethylene (TCE) – type of solvent
  • Heavy metals – such as chromium, copper, lead etc.

These contaminants are generally not found naturally in groundwater and usually originate from a man-made contaminant source.

How to wash your car with well water if you have no choice

It becomes difficult to change your water supply and not too many people want to buy water to clean their car. If you must use well water to clean your car, then there are some things you should keep in mind to minimize any potential and long-term problems.

  • Wash your car in the shade or in the evening as the sun bakes on spots faster.
  • Use high quality car wax on your car to protect it from potential well water contaminant damage.
  • Use detergents like a car shampoo specially formulated for washing cars.
  • Dry off the water quickly with a clean microfiber towel. Don’t leave any part of the car wet, but dry as you wash each section.
  • Finish off with clean chamois and polish.

How to remove water spots from your car?

Water spots on cars can become permanent if they are left too long. So, if you have water spots on your car, it’s best to use a good quality spot remover such as the Eraser (Amazon link).

You could also choose to use a solution of vinegar and distilled water in a 50:50 ratio. Usually this should be enough but try it out on a small area first as soon as you notice any spots and before they cause any long-term damage.

Make sure you use wet microfiber cloth with filtered/purified water and remove any leftover vinegar. Vinegar is acidic after all.

A good (large) microfiber towel will make your life a lot easier, especially if you regularly wash your car.

There are tons of different types, so buy whatever one suits your needs – the Meguiar brand is good (Amazon link). I usually go for a microfiber towel with a bit of texture as I find it sucks up more water than your regular Shammy and can help loosen any mineral residue.

If vinegar is not your thing, then use a clay bar (Amazon link) to pick up any mineral deposits and then finish off with a good car polish.

After using a car polish, it is best to use sealant for a good finish and to prevent any damage to your car paint. Teflon sprays are great at preventing paint damage on new or polished cars. Or you can opt for a ceramic coating, which is longer lasting than Teflon.

My #1 pick for a ceramic coating is the Shine Armor Fortify Quick Coat Ceramic Coating from Amazon – it’s awesome!

What about using soft water?

Soft water may sound contaminant free. However, soft water can still contain minerals, TDS, or other contaminants that can leave spots, stains and damage your car over time.

Best water for car washing

In an ideal situation you should use distilled water or de-ionized water to clean your car. If you do need to use well water, however, follow the instructions above for a spot-free and clean car.

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