Where to discharge water softener backwash?

Last updated on: April 1, 2024.

A common type of water softener uses an ion exchange process to remove hardness minerals in the water. The softener works by pumping water through a resin bed and exchanging hardness minerals like calcium and magnesium ions sodium or potassium ions. This process remains effective because of the regeneration process where the unit is backwashed with concentrations of potassium chloride or sodium solution. 

The volume of the backwash and the frequency of regeneration cycles will depend on the hardness levels, water usage in the household, and the size of the water softener. Water softeners are set to regenerate based on timed intervals or water flow measurements. If the water flow regulates the water softener, it produces less backwash brine than a timer-regulated system. It is critical to ensure that the brine solution is disposed of properly. 

Typically, the brine solution has been directed into septic tanks, discharged into a dry well underground, or pumped out of the house to the ground surface. Unfortunately, the brine solution can harm the groundwater or surface water if you don’t follow certain best practices. 

What is backwash water softener?

Backwash brine solution contains an excessive amount of chloride, sodium, and potassium ions from regeneration salts. The natural removal of hard minerals from the water source is also a contributing factor to this excess. The backwash is when the water flows upward through the resin tank quickly to flush the hard minerals from the resin bed and into the drain. Essentially, backwash takes place to make the water softener ready to start the water softening process once again.

How often should water softener backwash?

Since backwash is an essential stage in the regeneration process, it should happen every two to three days. New models of high-efficient water softeners may regenerate every day or even many times per day. The frequency of regeneration depends on the water consumption, water hardness levels, the amount of iron in the water, and resin tank capacity. The time taken for backwash is usually set at 10 minutes by default. You can adjust based on your need. The gallons of water used during the backwash also depend on water pressure and water flow rate in the water supply.  

What happens after backwash on a water softener?

The backwash is when you direct the water to help remove the accumulated solids in the resin bed. From here, the water flows out of the top of the resin bed and into a drain and flushes the solids out.

The backwash is followed by the brine draw, which involves the highly concentrated brine solution with sodium or potassium ions. This brine solution can be directed to the resin bed for around 20 minutes. Once this stage is completed, water gets pushed through the media for the ion exchange process, further pushing the brine solution into the drain. Finally, you have the fast rinse where you direct the water to the top of the resin bed, helping it to flush the hard miners and the brine into a drain. 

Where should you drain water softener backwash?

City Water Softener SoftPro

The water softener backwash contains high concentrations of sodium and chloride that need a proper drainage option for the unit. Most people find it convenient to get rid of the backwash directly into a local sewage system. But, it is not always possible to have a direct line to the sewage system, or the city municipalities have laid out restrictions. 

Fortunately, there are other options.

1. Draining the backwash outside 

It is fairly simple to drain the water softener backwash onto the ground outside. But, with the high salt levels in the backwash, it becomes harmful to the local wastewater treatment systems and the existing ecosystem. There may also be local regulations restricting such draining as they may be using the groundwater for drinking water. 

You would need to ensure that the drain is located as far as possible from the source of your well to prevent contamination. If you are unsure of the required distance, you may want to look at offsite discharging options.

Into Dry Well 

A dry well is deep and has a porous wall allowing the slow soaking of the backwash into the ground. It is best if the dry well is above the water table, as it can take in a large amount of water and then slowly release it into the surrounding ground over a long time. This is called prolonged dissipation, as it prevents a sudden increase in sodium concentrations in the soil.

French Drain 

A French drain involves a pipe placed horizontally along a ditch. This pipe has interspersed holes, and pebbles cover the ditch. It ensures that the backwash is dispersed horizontally, covering a larger area, and the pebbles help to see that there is enough space without causing an overflow.

Septic Drain Field 

A septic tank is a good way to disperse salt over a large area as long as it has a drain field. This method is a common practice. However, in recent years, there has been much discussion on the impact of water softener discharge. One option is to convert an old septic tank and disconnect it from the outlet pipe, making small holes at the bottom of this tank. Then, you can fill up the tank with some pea stone and attach the drain from the water softener.  

You can reduce the amount of brine discharge by selecting the demand-initiated water softener. It has a regeneration cycle that is regulated by flow instead of a timer. 

2. Discharge to the subsurface 

If the backwash is drained to the subsurface, you must maximize the distance between the point of the brine discharge and the well, keeping in mind the other wells on neighboring properties. The recommended distance is 100 feet or more. Whenever possible, place the brine discharge downhill from the drinking water wells. If you are constructing a subsurface system, make sure that you locate the components of the onsite wastewater systems so that the system is not damaged.

3. Discharge to the surface   

The discharge to the surface is best avoided to prevent freezing of the brine, prevent damage to the vegetation, and prevent exposure of the discharge to people and animals in the area. 

However, if you are using a surface discharge, you need to ensure that discharged brine is contained within your property. You can do this by directing the discharge to a non-paved area so the brine soaks into the ground. The distance from the discharge point to your well and any wells on neighboring properties should be100 feet or more. Additionally, make sure that the discharge is directed away from your well. It is essential that the well’s casing is sealed thoroughly so that the surface water is not ponding at the location of the well.

Keeping the environment in mind, prevent the discharge from entering surface waters or wetlands nearby.  

4. Discharge into your OWTS   

If you are discharging to your onsite wastewater treatment system (OWTS), make sure that it is of the right size so it can handle the volume of water. You may need to install an effluent screen to the septic tank’s outlet pipe to prevent solids from entering the leach field. And it needs to be pumped more frequently. Remember that brine is heavier than water and will settle to the bottom of the tank. This could reduce the tank’s effective volume for solids separation and retention, making grease and minerals mix. 

A detailed guide on how to drain your water softener: 

Scoop or vacuum the water out 

The best way to optimize the water softener’s performance is to ensure proper maintenance. It involves cleaning the brine tank regularly. But, before cleaning the tank, you need to empty it of the water. You can empty it by scooping it out or vacuuming. If you find that the water is clean, it can be reused. 

Regenerate the water softener

You can program your system to start a manual regeneration cycle. It would drain the tank during the brining stage. Select the option to skip the rest of the cycle when the tank is full. It will stop from automatically refilling.

Empty into the drain

If you need to move your tank, you must first bypass the water. You need to also remove the overflow hose and the salt grid if your water softener has one. Then, it can be disconnected from the water plumbing system that goes to the brine tank.

The final step is to remove the brine tank and the float before you tip the tank to empty it into the drain. 

Frequently Asked Questions:

1. Is backwash the same as regeneration?

The backwash is when particulates are removed, allowing the trapped gases to escape. It also relives the resin bed compression. Regeneration is a process that displaces the ions exchanged when the water softener was in the process of softening the water. 

2. Where should a water softener drain line be?

The water softener drain line should be 1 ½” above the opening of a drain standpipe, or the laundry sink rim, or above the floor drain. 

3. Can you discharge a water softener to a sump pump?

Discharging the water softener into a sump pump may clog the pump. Sump pumps above with plastic housing and above the level of the sump pit will work. But, if it is discharged into a sump pit, it can work without clogging.

4. How do you dispose of water softener salt?

You can dispose of the water softener salt by sprinkling them in an area that has overgrown weeds. You can also save the salt for winter months when you need to use it on icy patios or driveways. Another option is to simply put it into the trash bag and throw it out with the rest of your garbage. 

5. How much water is discharged from a water softener during regeneration?

During the regeneration process, a family of four members can discharge anywhere between 50 and 100 gallons of water at a time. 


Water softener backwash needs to be drained with some thought as it affects the surrounding ecosystem and the groundwater. What’s more, it also affects the vegetation. Now with all the above information, you are better prepared to arrange suitable draining systems when you install a water softener to meet your water softening needs. 

About The Author

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Judith— a passionate water treatment specialist — is a waste water management enthusiast, clean drinking water advocate, and someone with deep personal experience and knowledge about various water equipments. Her work was mentioned in countless notable water associations. Previously she was an editor at Water Alliance.