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SALT OR WATER INTO SEPTIC - Will the Water Softener Salt or Water Volume Damage the Septic System?

At HEALTH RISKS & WATER SOFTENERS we introduced possible health concerns for salt added to drinking water by a water softener. Some septic system experts assert that salt discharged into the leach field is an important factor in shortening the life of the biomat which forms below the leach field (to treat effluent as part of the sanitizing process for septic effluent).

Certainly high levels of salt can kill septic tank or drainfield bacteria.

But a normally-operating water softener is unlikely to harm the septic system.

We start by agreeing that a malfunctioning water softener may damage a septic system in two ways:

1. Water volume in Septic Fields from Water Softeners: The normal water softener backwash cycle is less than 100 gallons and is not a major source of daily water usage at a property (see "Determining Needed Septic Capacity" at "More Reading" below). If the timer or valve gets stuck in the "backwash-on" cycle (which I have seen happen), the system will run continuously and will flood the septic leach field. This is discussed in "Clogged Drain Diagnosis" referenced at "More Reading" below.
   
   
2. Salt dose of Sodium and Chloride in Groundwater from Water Softeners: Part of the water softener backwash water contains no extra salt. During an interval of backwash however, some water may be quite salty, perhaps 5,000 ppm to 10,000 ppm. If the salt dose (which is also adjustable on many water softeners) is set incorrectly high excessive salt may be discharged into the septic system where it may damage the leach field and its biomat.We encountered this condition at a property where the owner had first set the salt dose to the maximum and then set the backwash frequency to a maximum as well, when neither was needed for the level of hardness of the water.
   
   A Michigan DES study of community wastewater treatment systems (not private septic systems) reported that sodium and chloride in the soil at their discharge sites greatly exceeded federal drinking water limits. This point needs more research since it's not clear that groundwater is required to meet drinking water standards - this is a shortcoming of the Michigan article. The article continued to cite 120 m/l for sodium and 250 m/l for chloride as the maximum allowable levels in groundwater. (See "Sodium and Chloride and Water Softeners" at "More Reading".) On further research I will update this section.
   
   
3. Water softener salt at normal levels will not kill septic tank bacteria

Normally the water softener salt and chloride should not be a problem for the septic system: One of my clients is a biochemist who specializes in studying septic bacteria.

His opinion was that in a normally-working home water softener system the level of water softener-produced salt in the septic tank was so diluted by other water flowing into the tank that in his experience it never reached a level that was harmful to septic tank bacteria.

I'm not sure if this same conclusion applies to bacteria in the drainfield biomat. Gayman and others have conducted research on salts in drainfield soils and their role in drainfield life.

Normally water softener water volume should not be a problem for the septic system. See REDUCE IMPACT OF SOFTENER and then be sure to read  SOFTENER ADJUSTMENT & CLEANING to be sure that your water softener is operating properly.

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WHAT CAN GO INTO TOILETS & DRAINS?
  DETECT HARD WATER
  MEASURE WATER HARDNESS
  HOW SOFTENERS WORK
  HEALTH RISKS & WATER SOFTENERS
  SALT OR WATER INTO SEPTIC
  REDUCE IMPACT OF SOFTENER
  SOFTENER ADJUSTMENT & CLEANING
  OTHER SOFTENER METHODS
  Winterize Water Softener & Treatment Equip
  Restoring Water Softener & Treatment Equip

• North Dakota Standards for Water Softeners, North Dakota General Authority Law, Chapter 62-04-08, Water Softener Units http://www.legis.nd.gov/information/acdata/pdf/62-04-08.pdf. "The objective of this chapter is to provide a standard of quality, capacity, and performance for water softener units. Water softener performance is to be based upon referee tests procedures described in section 62-04-08-09."
• Culligan Mark 10 Water Softener 1994-1998 Installation and Operating Instructions (covering models manufactured after 1995) (1-96) 01881948.pdf available from www.culligan.com
• Water Softeners, CMHC, Canadian Mortgage and Housing Corporation, cmhc-schl.gc.ca/en/co/maho/wawa/wawa_005.cfm - October 2008. Canada Mortgage and Housing Corporation acknowledges the contribution of Health Canada to the development of this document. For further questions regarding water treatment and water quality, contact Health Canada at watereau@hc-sc.gc.ca or call 613-957-2991 or 1-866-225-0709.
• "Commercial Water Softener Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia) for commercial, industrial and residential application www.ibcwater.com.au (07) 3219 2233
• "Non electric water softener, Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• "Water Softener Twin Tank Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• Our Water Hardness Table used at originated with but was edited and added to from http://www.bestfish.com/tips/110598.html and also from http://www.water-research.net/hardness.htm

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More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems


• Cesspools Home Buyer's or Owner's Advice
• Drywells Home Buyer's or Owner's Advice
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location


• Additives & Chemicals: Septic System Maintenance - Are they even needed? Are they even legal?
• Biomat Formation in the Septic System Drainfield Absorption System - what leads to drain field clogging and expensive drainfield repairs
• Buyer's Guide Home Buyer's Guide to Septic Systems Inspection & Testing - What to Do, Step by Step.
• Cheating on Water Tests - (Chlorine in Wells and Septics) Testing Water for Real Estate Transactions - Water Test Cheating Warnings for Home Buyers and Home Inspectors
• Clogged Drain Diagnosis - is the problem the septic system or the Building drain system?
• What is a Septic System An Engineer's View & Septic System FAQ's
• Contamination in Buildings how to test buildings for bacterial contamination from Sewage and Septic backup, remediation, & references
• Leach Field Inspection Procedure Septic Leach Fields - how to inspect and diagnose septic drainfield failures - what causes septic field failure?
• Maintenance: Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• Sewage & Septic Backups and what to do about sewage spillage in buildings
• Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Tank Pumping Frequency Guide for Septic Tanks: When, How, What to Watch For when pumping or cleaning septic tanks
• Water Usage: Capacity: Determining Needed Septic Capacity - Typical residential water usage for people, appliances, and activities.

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