Why Pool Water on Grass Might Be a Bad Idea?

If, like me, you love a beautiful garden and the pool is part of the overall landscape of trees, lawns, and accent plants, combined with paving, pool decking, and water features, you want to ensure that the green lawn and colorful plantings aren’t affected by pool water that you need to drain during the cleaning process, or if the pool is overfilled, and the level needs to be lowered. Does pool water kill grass?

Pool water will kill grass under extreme circumstances, such as excessive volume, high chemical levels, or too frequent draining of the pool. Everyday exposure to splashing, occasional partial draining, and pool water containing low levels of chlorine and other chemicals won’t cause harm to grass.

In this article, I will look more closely at the possible risks of draining pool water onto the lawn, whether it’s chlorinated or salt water, what techniques can be used to minimize the risk of damaging the grass, and what alternatives there are. If you’re a pool owner, you’ve probably been aware of the problem, so I’m happy to share the solution with you.

Will All Pool Water Kill Grass?

In most cases, taking some commonsense precautions, the water you drain from the pool will not permanently damage your grass, but saltwater needs a different approach to chlorinated water.

Some General Precautions To Prevent Water From Killing Grass

Irrespective of whether you have a saltwater or chlorinated pool, there are some general dos and don’ts when it comes to protecting your grass.

  • Don’t flood the lawn. Experts suggest that one should limit the amount of water drained onto the grass to no more than 1.5 inches per square foot per week.
  • If possible, drain pool water onto slightly sloping rather than completely level ground to prevent pooling.
  • Use a drainage hose that can be moved around to distribute the water over a larger area.
  • Don’t add chemicals to the water for a few days before draining it so that the level of salt or chlorine is as low as possible.
  • Drain water onto grass during the coolest part of the day, either early morning or early evening, to avoid evaporation and allow the water to soak into the soil.
  • The most important rule to protect the grass is to dilute your pool water as much as possible before draining it onto the grass.

Will Saltwater Kill Grass?

Having converted my pool from saltwater to chlorinated, I could directly compare the effect of the two types of water on grass. I learned that the saltwater could be more damaging if insufficient care was taken.

The Effect of Salt On Grass

Salt water won’t kill grass in small quantities, but unlike chlorine, it can build up in the soil over time and, if drained constantly, will contaminate the soil in the long term.

High salt levels: Because salt binds so closely to water (in other words, it’s highly absorbent), it prevents the roots from absorbing the water. High salt levels will also result in nutrients such as calcium, magnesium, and potassium being absorbed by the salt from the soil, which will then be unable tosupport a healthy lawn.

Salt water may burn the grass blades, turning them yellow and causing them to lose chlorophyll, so they can’t utilize the sun’s energy to photosynthesize.

Salt water may result in sodium toxicity in the soil as it breaks down into sodium and chloride ions. The high sodium levels change the structure of the soil, making it less porous and, therefore, less able to absorb water and oxygen.

The Effect Of Saltwater On Grass

Draining salt water onto your lawn not only dumps salt on the grass but also chlorine, stabilizer, and probably algaecide. Nevertheless, on average, the salt level is only one-tenth that found in seawater. While the salt won’t disappear, the water itself is beneficial to the grass, and the other chemicals, as long as they are very diluted, will, in fact, act as weedkillers without damaging the grass itself.

Will Pool Chlorine Kill Grass?

Pure chlorine will kill grass if it’s dumped in sufficient quantities, but diluted chlorinated pool water drained onto grass won’t have any negative impact as long as it’s done in low volume and over a period of time.

High chlorine levels will affect the soil’s pH, negatively affecting grass.

I recommend testing your pool water before draining it onto your grass. If the pH is lower than 7.0 to 7.8, it’s too acidic; otherwise, it’s safe. To ensure the chlorine level is not too high, don’t add any chemicals to the pool for at least two days before you drain any water onto the lawn. A pH of over 8.0 is too alkaline, and that, too, can result in an imbalance in the soil pH and affect the nutrition available to the grass.

Will Pool Shock Kill Grass?

If the chlorine level in your pool is typically between 1 to 3 parts per million, occasional exposure might not severely damage grass, as many have emptied pool water onto lawns without immediate harmful effects.

However, pool owners sometimes use a “shock” treatment to elevate chlorine levels to 10-30 ppm or more to combat algae and other issues. If your pool has these heightened chlorine levels, it’s more than likely toxic for grass. Not only can this shock treatment harm the lawn directly, but it’s also designed to kill algae and bacteria, which means it can severely impact the nitrogen-producing bacteria in the soil.

How Do I Neutralize Pool Water Before Draining?

Before looking at how to neutralize the chemicals in the pool water, I’d like to establish the reasons for having to drain the pool because, in theory, besides these reasons, it shouldn’t be necessary at all.

Reasons To Partially Drain A Pool

  1. Heavy rain may cause your pool to fill to overflow, which causes additional pressure on the structure and makes the skimmer box inoperative so that debris and dirt cannot be removed.
  2. Backwashing is essential if you have a sand or diatomaceous earth filter that needs to be cleaned, and each backwash can drain hundreds of gallons of water from the pool.
  3. Water chemistry: If the pool has been over-stabilized, chlorine is not released, and the sanitizing process becomes ineffective. In this case, the only solution is to drain the pool partially and fill it with fresh water to correct the imbalance.

Reasons To Empty A Pool

  1. Pool maintenance: Experts recommend that the pool be drained every five to seven years, as even if you have treated the water regularly, the level of TDSs (total dissolved solids) becomes difficult to control even with the right chemicals.
  2. Algae Infestation: In extreme cases where algae growth is rampant, there may be a chlorine lock or over-stabilization, and all chemical treatments have failed. In this case, it might be necessary to drain the pool completely to scrub and treat all surfaces before refilling. In the case of a fiberglass pool, a professional should do the emptying to avoid the pool popping out of the ground.
  3. Pool repairs: If you have a bad crack, if the tiles have been damaged, or if the pool surface has become badly stained by a build-up of minerals such as copper or iron, a complete draining might be required to acid wash or treat the pool surface to remove these stains. Again, I recommend getting a pool expert to advise you on the best way to drain the pool and get rid of the water safely.
  4. Switching Water Types: As I have done, some pool owners might decide to switch from a chlorinated to a saltwater system (or vice versa). Although it’s possible to make this changeover without fully draining the pool, it’s a quicker process to do so, having made the plumbing alterations like installing (or removing) the chlorinator.

Neutralizing The Chemicals In Pool Water

If the reason for having to drain pool water is the heavy rain, it is likely that the chemicals have already been diluted sufficiently to allow safe drainage, but I recommend testing the water first to confirm this.

If you’ve planned to do a backwash, I suggest holding back on any chemical application for a few days beforehand, which will reduce chlorine levels. If the water has become over-stabilized, buying a chemical neutralizer from your local pool store might be necessary, and then waiting a few days before draining the pool.

Where Else Can I Drain My Pool?

If you have decided not to drain pool water onto the grass because you don’t want to risk damaging it, or it might, like Kentucky Bluegrass, be particularly sensitive to chemicals, the alternative is to run the drainage pipe into the municipal drain system.

Just a warning – Some municipalities allow pool water to be drained into the stormwater sewer system, but others prohibit it, so check with your local authority first to avoid incurring a penalty.


A complete drainage is seldom needed, except for the reasons mentioned. Whether it’s emptying the pool or just partial drainage, it can be done without killing the grass provided the saltwater or chlorinated water’s chemical levels have been checked, and it’s done gradually and carefully, even over a period of days if necessary, to avoid waterlogging the soil and minimizing the impact of the chemicals.