Is It Safe to Drain Hot Tub Water on Grass?


You’ve probably said to yourself that emptying your hot tub onto grass would be highly convenient and an excellent way to recycle water. But is it safe to drain spa water onto your lawn?

A freshly chlorinated hot tub should not be drained onto grass. High levels of sanitizing chemicals will damage and kill grass, plants, and tree roots. However, if you allow the sanitizer level is to fall to 0.1 ppm, it will be safe to empty the spa water onto the lawn and surrounding vegetation.

The type of sanitizer you use makes a huge difference as to the amount of damage it can cause. This guide will show you how to discard water for chlorine, bromine, and saltwater spas.

Why spa water can damage your lawn

If your spa is surrounded by grass, you may have noticed that splashes of water seem to do no harm. This is because most soils can tolerate chlorine or bromine in small quantities.

But while small splashes don’t do any harm, it’s a very different story when it comes to draining an entire hot tub’s worth of water onto your lawn.

Risks of draining chlorine or bromine spas on grass

Chlorine in concentrations above 2 parts per million (ppm) is particularly damaging to plants such as shrubs, trees, and ornamentals.

When chlorine accumulates in the plant tissue too quickly, it “burns” the plants, causing them to die. Highly chlorinated water can also be harmful to the health of the soil, resulting in a pH imbalance.

Concentrations of bromine greater than 2 ppm can also accumulate in plant tissue and root systems, which leads to the death of these plants over time. Bromine is especially harmful to trees.

It’s worth noting that plants such as roses, vegetables, and fruit trees are more susceptible to chlorine and bromine than hardier plants like rosemary, juniper, and olive trees.

However, if you allow the chlorine or bromine levels to lower to almost zero, then it is safe to drain the spa water onto your lawn. More information on how to do so later in this article.

Tip: If you accidentally spill undiluted chlorine onto your lawn, dilute the area immediately by watering thoroughly with fresh water.

Never drain saltwater spas on grass

Never drain a saltwater hot tub onto your lawn or down storm drains. Saltwater spas can only be drained into a sanitary sewer system or removed by an approved waste hauler.

Just like chlorine or bromine, small quantities of salt will not kill your grass. But there may be as much as 13 lbs (6kg) of salt sanitizing your spa water, which could cause irreparable damage if it’s emptied onto a small area of your lawn.

The large doses of salt found in a saltwater spa will alter soil chemistry so greatly that it will no longer be able to support new growth.

This is because salt destroys the natural bacteria found in soil, meaning that grass, weeds, and other plants lack the nutrients they need to survive. What’s more, salt can remain in the soil for years.

You risk flooding your lawn

Another issue with emptying spa water onto grass is that the lawn may quickly reach its saturation level. Hot tubs have to be situated in areas that are flat, and flooding is a lot more likely on level ground.

Flooding can drown the roots of grass and attract unwanted mosquitoes, which will begin to breed within two or three days. The flooding may be so bad that it runs into your neighbor’s yard, too.

It’ll also make the area uncomfortable underfoot for getting in and out of the hot tub once you’ve filled it back up again.

Where should you drain hot tub water?

Rules around the disposal of chemically treated water differ from country to country and from state to state in the US.

As such, it’s best to consult your local municipal Department of Environment Quality for specific guidelines and codes. Use this linkOpens in a new tab. to visit the US Environmental Protect Agency website.

How to drain a chlorine or bromine spa on grass safely

The following advice is for hot tubs that use chlorine or bromine to sanitize the water. Never drain a saltwater spa onto grass.

Most municipalities permit the draining of hot tubs onto the lawn as long as it doesn’t affect the neighbor’s property.

But before you do so, you’re going to have to wait until the sanitizer levels are almost zero. Ideally, you should wait until the chlorine or bromine level reaches 0.1 ppm or lower to avoid causing any damage to your lawn and surrounding plants.

The simplest way to dechlorinate hot tub water is to allow it to decrease naturally over the course of several days.

The process can be sped up by turning on the jets and removing the cover to allow the chemicals to evaporate and be destroyed by the sun’s ultraviolet rays.

If significant amounts of water evaporate from the spa, top it up with fresh water to dilute the sanitizer levels even further.

The other option to dechlorinate hot tub water is to add an additive called neutralizerOpens in a new tab.. Neutralizer contains sodium thiosulphate, which works to rapidly lower chlorine and bromine levels. It’s a handy product to have around in case you accidentally over-chlorinate your hot tub.

The last thing to do before emptying the spa water onto your lawn is to ensure that pH level is neutral as highly acidic water can damage the grass.

On a dry day, use the drain spigot (drain plug) to slowly release the water onto your lawn to be absorbed into the ground.

How to drain spa water into a sanitary sewer system

Disposing of hot tub water into your nearest sanitary sewer is the probably most convenient way to get rid of chemically treated water.

Sanitary sewers channel wastewater into treatment facilities where it is cleaned and tested to make sure it’s safe.

It’s where all the water you use inside your home ends up, whether that be from toilets, showers, dishwashers, or washing machines.

If you own a saltwater sanitizing system for your hot tub, then the salt water must be slowly emptied into the sanitary sewer connected to your home.

Connecting your hot tub to the sewer system may be a job you can undertake yourself, or it may require assistance from a qualified plumber.

If your hot tub is not directly connected to the sanitary sewer, you can attach the spa to other sanitary sewer connections in and around your home for drainage. Never direct spa water discharge to a private septic system.

Can I drain my hot tub into a storm drain?

For the sake of convenience, you might be wondering whether it’s possible to empty your hot tub water into a nearby storm drain.

It’s not safe to drain water from your hot tub into a storm drain. Storm drains flow directly into streams without undergoing wastewater treatment. The high levels of chemicals found in chlorine, bromine, and saltwater spas are toxic to fish, plants, and microorganisms that live in these bodies of water.

Unlike sanitary sewer systems, storm drains (surface water drains) are in place to direct rainwater and snowmelt from our streets into rivers, lakes, reservoirs, canals, or the sea in order to prevent flooding.

Other than catch basins, the piping system features no treatment facilities to treat the water as it heads directly into natural bodies of water.

Spa water contains harmful amounts of chlorine, bromine, salt, algaecides, nonylphenols (cleaning agents), copper, and other contaminants that have a severe impact on the ecosystem. Even at very low concentrations, chlorine is particularly harmful to aquatic life.

Essentially, there is no difference between pouring polluted spa water down a storm drain and dumping it directly into a nearby lake or river.

As well as killing aquatic life and harming other wildlife, there are penalties for anyone caught discarding hot tub water into gutters or storm drains. Fines are usually in the thousands of dollars.

Did I cover everything?

I always try to provide the most relevant and up-to-date information I can in all of my articles. Saying that, feel free to shoot me an email using the contact form if you think this article is lacking in some way, or if you’ve been left with any doubts.

Thanks for reading and happy hot-tubbing!

Recent Posts