I am often asked how the water softener effects the septic tank. I am also often told all kinds of things about how the water softener effects the septic tank.
Well I am not, and have never pretended to be a septic tank expert, but since what I do at the beginning seems to always end up at the end, it is hard for me to ignore the septic tank. For that reason I have had to read, study, and discuss with those more informed than myself concerning the septic tank questions. I will now share with you everything I have learned about the question in an attempt to help you better understand all of the angles and thoughts as they relate to connecting your water softener drain to your septic tank so you can decide what you want to do. In order to do this I will have to break the discussion into different parts so I can address the different specific concerns I am most often presented with.
SHOULD I USE POTASSIUM INSTEAD OF SALT BECAUSE OF MY SEPTIC SYSTEM?
While working in the field of water treatment I have found that some people run the water softener drain into the septic tank and use Sodium Chloride (salt) in their softener. Other folks run the water softener drain into the septic tank and use Potassium Chloride (salt). Yes, really. They are both salt. Lets take a look at the definition of salt from Wikipedia which states: In chemistry, a salt is an ionic compound that can be formed by the neutralization reaction of an acid and a base. Salts are composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). Table salt, or sodium chloride, is the ionic product of the combination of lye, or sodium hydroxide, and hydrochloric acid. Potassium chloride is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water and its solutions have a salt-like taste.
Now that we have determined that they are both salt we can come to a few simple conclusions. First, a water softener that is being operated on potassium chloride is not a salt free water softener. Secondly, no matter which one you use you are adding chlorides to the drain water. Thirdly, since you have to program the water softener to use about 25% more potassium chloride than it would use sodium chloride to do the same job, using potassium chloride would obviously add 25% more chlorides to the drain water than using sodium chloride would. So if you are concerned with chlorides in the sewer system that would be something to consider. The potassium and sodium would act the same in relation to the science of settling in the septic tank. The end result would be pretty much the same except that you would be adding more if you are using potassium.
Another thing I hear as a reason for using potassium chloride is that it is better for the septic system because the potassium is good for plants and will help the grass grow on the leech field, where sodium is not good for plants and will kill the bacteria in the septic tank. First of all, let’s get past the idea that the sodium from the softener discharge kills the bacteria in the septic tank. The ocean is much more salty than your water softener discharge and all forms of life seem to do very well there, so I doubt if that is an issue. I would think there are many other things we do that would have thousands of times more deadly effect on the bacteria in our septic tank than some sodium diluted into the water. How about using bleach in the laundry? What about all the anti-bacterial soap? Not to mention such things as drain cleaners, toilet bowl cleaners, and the list could go on and on. Plus, if one was going to pay up to five times the price of sodium chloride, to use potassium chloride, because it is good for plants, wouldn’t one capture the discharge and use it to water plants?
DOES THE WATER SOFTENER DISCHARGE TOO MUCH WATER INTO MY SEPTIC TANK AND CAUSE IT TO FAIL?
In most cases the water softener will discharge no more than 50 gallons of water during a complete regeneration cycle. It does this over an approximate 2 hour period. 2 hours is 120 minutes. 50 gallons divided by 120 = 0.42 . This means the water out put of the water softener during regeneration averages less than 1/2 gallon per minute. That is less than almost any faucet or appliance in your home.
I know you will find people who believe differently but facts are facts. According to what we have just discovered above you should be much more concerned about pulling the stopper on your bath tub than your water softener discharge.
DOES THE WATER SOFTENER DISCHARGE DESTROY THE LEECH FIELDS ABILITY TO ABSORB WATER?
This is a very good question. In fact this is one of the biggest questions that fueled the controversy in the beginning. It seems that some septic tank professionals had discovered some problems with leech fields and had come to the conclusion that because those houses had a water softener, that must have been the cause. I think this was the result of a misunderstanding of how the water softener operates. They thought the water softener was putting large amounts of salt into the system, but that is not exactly how it works.
The water softener uses the principle of ion exchange to remove hardness minerals from the water such as calcium, magnesium, and iron from the water. It does this by exchanging them for a softer mineral like sodium or potassium. As the water softener is operating it is catching the calcium and other hardness minerals on the resin beads and releasing the softer mineral ion into the water stream. When the softener regenerates it bombards the resin bed with the soft mineral ions and knocks off the hard mineral ions. This means that a large part of the regeneration discharge of your water softener is actually the hardness minerals such as calcium, which happen to be very good at increasing the water absorbency of the soil, thereby improving the function of the leech field.
DOES THE SALT FROM THE WATER SOFTENER DISRUPT THE SETTLING PROCESS IN MY SEPTIC TANK?
Actually no. Not if it is done correctly.
This is one of those mysterious type chemistry questions that can be argued in so many different directions that it can make you set your hair on fire. I have heard people say that the sodium in the regeneration discharge does this, but as we just discussed the regeneration discharge contains much more than sodium. I have also heard people say that the use of potassium chloride keeps this from happening, but the potassium and sodium ion are so similar in ionic form that they would have exactly the same effect.
What is true is that if you put too much sodium or potassium into the septic tank you could disrupt the ionic composition of the liquid, it can have the effect of causing the solids to settle slower than normal. The key words here are “TOO MUCH”. Too much of anything is not good for your septic tank. Too much bleach. Too much soap. Even too much water. So you can see how it can be very hard to reason with someone who just wants to say that the sodium and extra water “COULD” hurt the septic system so they don’t want it in there. However, the truth is that a properly designed and maintained water treatment system does not put too much of anything into your anaerobic septic system. It does not harm your septic system. It actually improves the operation of your septic system.
Now that you have seen what I have heard and what I think about it all. I imagine you would feel a lot better about it if you could see what someone who really knows what they are talking about has to say. Some really smart people from both sides of the table wanted to get to the bottom of this and find the answers to these questions. They got together and commissioned a scientific study to the tune of $100,000. They studied the results and came to the conclusions outlined in this document.
2013_NOWRA_WQA_GuidanceDocument
This document is the result of a joint study carried out and funded by the Water Quality Association (the water treatment professionals) and the National Onsite Wastewater Recycling Association (the septic system professionals). In other words, this is what both sides of the question agree is the advise you should follow as it pertains to your water softener and your anaerobic septic tank and leech field.
If you would like a little more information from another source you can read this fact sheet put out by the United States Environmental Protection Agency.
epa_wastewater_softeners_factsheet
Of course I understand that no matter how many studies are done, no matter how much money is spent, no matter how many scientists agree and tell us that the water softener does not harm the septic tank. No matter if they even go as far as telling us that it makes the septic tank work better (which, of course, they did). There will always be “that guy” who has “seen something” or “heard about” some evidence that proves them all wrong, and will throw all kinds of fog into the discussion. After all, there are still people who believe the world is flat. I personally think it’s a good thing to have vigorous debate, even if it seems ridiculous. We should always be questioning everything. It keeps us looking and learning. But right now my mission is to clear up the fog so you can decide what to do with your water softener discharge.
So, let me summarize for you, not what I say, but what the experts (both on the water treatment and septic system side) and scientists said, after they had spent $100,000 studying the situation.
- The water softener will not harm your anaerobic septic system if it is a new DIR type efficient water softener that is programmed properly.
- They do not differentiate between sodium chloride and potassium chloride.
- It is better to put the regeneration drain water from your water softener into your septic tank than to put the drain water going somewhere else.
I hope this helps you decide what is right for you. I know there is a lot of confusing information out there and it is very hard to know what to do.
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