Brine Tank Water Level

This article addresses the common questions we get about the water level in the brine tank of a water softener. Some of the versions of this question include the following:

How high should the water level in the brine tank be?
I think my water level is too high / too low what should I do?
My water level is above the level of the salt
My water level is below the level of the salt
The water level in my brine tank doesn't ever change

How High Should the Brine Tank Water Level Be?

The answer to this question depends on many factors. The first thing to understand is that the amount of water that is added to the brine tank of a water softener is going to determine the amount of salt that gets dissolved by the water and therefore gets used in the next regeneration. So it is always the amount of water that determines the amount of salt that gets used. So different water softeners, under different conditions, may be programmed by the manufacturer, installer or homeowner to add differing amounts of water so that differing amounts of salt are used. These different salt levels (and corresponding brine volumes) may be selected for several different reasons:

the volume of water softener resin the system is built with (aka "size" of the softener)
the presence of iron or manganese in the water
the desired salt efficiency for the system

A common brine tank configuration is 15" x 15" x 34" high tank. This brine tank could be used on a 1.0 cubic foot softener or a much larger 3.0 cubic foot softener. All things being equal the amount of water that "should" be in the brine tank of the 3.0 cubic foot softener is 3X that of the 1.0 cubic foot softener. And in either of these cases, the presence or absence of iron in the water would change the amount of salt the operator would want to use, and this would change the volume of water added. You can quickly see that there isn't a "normal" water level for this brine tank - it completely depends on the application in which it's being used.

The Water In My Brine Tank is Above/Below the Salt

Is it a problem if the water in your brine tank is above the level of the salt? What about if it's below the salt? Probably not. And it's not a great diagnostic tool for understanding if your water softener is operating properly, and here's why:

As You Use Your Water Softener The Salt Level Drops

If your softener adds the same amount of water to your brine tank every time, and you don't add more salt, the salt level will slowly drop until eventually, it's below the water level in the tank. The same volume of brine will be created each time (which is the important thing) as long as you don't totally run out of salt.

Different Types of Salt Will Alter the Water Level

The type of salt you use will affect how much water the salt displaces. Some salt types have very large pellets and the spaces between the pellets is large too. Other water softener salt is a finer grain and the space between the grains is small. This is called the void space. If you fill your brine tank with salt with a small void space, it will make the water level in the brine tank higher compared to using salt with a large void space. The volume of water in the tank is exactly the same but the height of the water in the tank will be different.

The Water Level in My Brine Tank Never Changes

This observation can mean a couple of different things - one of which is a problem while the other is not. A water softener regeneration is comprised of several stages that follow this typical pattern:

Backwash - water flows up through the media bed to flush it of debris
Brine Draw - brine solution is drawn out of the brine tank and pushed through the media tank
Rapid Rinse - water flows down through the media bed to rinse it and re-pack it
Brine Fill - water is added back to the brine tank for a future regeneration

If you observe a full regeneration cycle (where you carefully watch each stage) and the water is never drawn out of the brine tank then the softener will not be regenerated and you will cease getting soft water from the machine. This is obviously a problem that needs to be resolved.

However, if you only observe the water level at the beginning of the regeneration and at the end of the regeneration you won't know if the water water taken out and replaced, or if it was never drawn out at all. So it's critical that you observe a full regeneration if you wan to know what's going on with the water in your brine tank.

The Water Level in My Brine Tank Rises Over Time

A common observation of residential water softeners is that the water level in the brine tank slowly rises over time until eventually, it gets so high that it triggers the overflow float, or it spills into the overflow drain that many softener brine tanks are equipped with. This observation means you have a problem. To understand how to correct it, it's important to understand how the root cause of the problem.

All water softeners have a single tube that connects the brine tank (aka salt tank) to the softener control valve mechanism. This is usually a 3/8" diameter plastic tube. When the softener is adding water to the brine tank it is the line pressure (household water pressure) that pushes the water into the brine tank. When the softener is drawing water out of the brine tank it accomplishes this by generating a vacuum in the control valve mechanism and this pulls the brine solution out of the brine tank.

There can be several different types of mechanical failures that prevent the formation of this vacuum and the softener is not capable of drawing the brine solution out of the tank. However, these types of failures typically do not stop the flow of water to the brine tank. So if water cannot be pulled out of the brine tank, but it can be added to the brine tank, the water level will rise every time the softener attempts a regeneration.

The common reasons that a softener cannot generate a vacuum and pull the brine solution out of the brine tank are the following:

The brine tank connection points at either the softener control valve or the brine tank are not air/water-tight
The softener "injector" or "injector screen" is clogged and this prevents the formation of a vacuum
The safety float in the brine tank is defective and won't allow water flow out
There's an issue with the softener air-check (in most softeners, this is in the brine tank in Autotrol models and few others it can be in the control valve)