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How Does use of a home Washing Machine Affect the Septic Tank?
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• Does a washing machine harm the septic tank or septic drainfield?
• What laundry soaps are best to use when a home is served by a septic tank and drainfield?
• What steps can be taken to minimize the impact of laundry use on a septic system?

Can we use a clothes washer or "washing machine" when a home is connected to a private septic system? What steps should be taken to protect the septic system from excessive water use or clothes lint or detergents? How to extend the life of a septic system.

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This document is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Homeowner's Guide to WASHING MACHINES Draining into Septic Systems

Does a washing machine overload and harm the septic system?

The volume of water from home washing machine use should not be a problem with a normal septic system in good working order. As we discussed at Dishwashers, in some conditions you should avoid emptying washing machine discharge into the septic system:

• Drainfield capacity limits: If the absorption system (leach field, drainfield) has limited capacity to absorb effluent
• Drainfields near failure: If the absorption system is showing evidence of failure, such as effluent coming to the surface of the property or backing up into the building (nonetheless you need septic field investigation and repair)

Below we discuss steps you can take to minimize the possible effects of extra wastewater loads caused by washing machines, and then we discuss the effects of detergents and soaps when operating a clothes washer connected to a septic systerm or dyrwell.

The following measures may relieve the water volume load on septic fields from the washing machine:

• Use liquid laundry detergent rather than a dry soap powder laundry detergent to reduce septic system clogging. Some experts report septic system clogging in pipes, septic tank, and drain field when large amounts of dry laundry soap powders are used.
• Install a lint filter on the washing machine water drain line to avoid sending lint into the septic tank and fields or install a graywater filter ahead of your drywell if you are using one to receive washing machine discharge waters..
• Install a separate drywell to receive water from the washing machine drain, and perhaps dishwasher and other graywater.
• Spread out use of the washing machine over longer intervals - perhaps washing loads in morning and at night rather than running one laundry load right after another. This "dosing" of the septic system or drywell gives the absorption system time to recover between washes.
• Cleaning out the septic tank more often than the minimum schedule will extend the life of your drainfield. In turn, this will permit the drainfield to better absorb the extra volume of wastewater generated by clothes washing. Similarly, any other measures that protect the drainfield's ability to absorb water, such as avoiding flooding the fields with surface runoff, become more important if a family is using their washing machine alot.

Does Washing Machine Detergent Harm the Septic Tank or Septic System Drainfield?

The volume of detergent from a clothes washer entering the septic system is so low as to be very dilute when it enters the septic tank, dilute enough that it is not going to harm the septic tank bacteria at normal levels of residential dishwasher use.

Clothes washing machine detergents do not make a high level of suds inside the machine.They rely on surfactants, high water temperature, and time spent agitating the contents of the clothes washing machine to clean them.

However many if not most washing machine (and dishwasher) detergents contain phosphates or nonylphenol ethoxylate surfactants. Surfactants are what make detergents effective in lifting soil particles off of a surface (a dish in the dishwasher or a shirt in the washing machine). These chemicals may be serious contaminants of ground water and surface water in the environment.

What detergents or soaps should we use in a washing machine connected to a septic tank?

Sometimes we find that dry powder clothes washer soap appears as clots and clogs in the system - usually because the homeowner is pouring in too much detergent and is not following the manufacturer's instructions.

Passing solid clumps of detergent into the septic tank speed clogging of the system and in severe cases can even block a building drain.

See Dishwasher & Laundry Detergents Containing Phosphates & Surfactants for a discussion of the effects of phosphates & detergents on the environment.

To minimize the possible clogging or other effects of laundry soaps on the septic system

• Avoid using more than the necessary amount of powdered laundry or dishwasher detergent. Excessive amounts of powdered laundry detergent often fail to dissolve in the washing machine.
• Liquid laundry detergent: Safer if you are not the one operating the clothes washing machine, use liquid laundry detergent.
• "Budget" powdered laundry detergents contain extra amounts of fillers (in some cases montmorillonite clay) which increase the risk of system clogging.
• High phosphate laundry detergents may be a factor in reducing drainfield life [more data is needed on this point.]

We prefer to use liquid detergents in the recommended amounts or less in clothes washers connected to or draining into any onsite disposal system, septic tank, cesspool, or drywell.

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WHAT CAN GO INTO TOILETS & DRAINS?
NEVER FLUSH INTO SEPTICS
BETTER NOT TO FLUSH
HOUSEHOLD CHEMICALS
OTHER CHEMICALS
CHLORINE IN DRINKING WATER
CHLORINE IN SEPTIC WASTEWATER
DISHWASHERS vs SEPTICS
DRUGS INTO the SEPTIC TANK?
GARBAGE GRINDERS vs SEPTICS
REVERSE OSMOSIS CONCENTRATE DISPOSAL
TOILET TISSUE?
TOILET TISSUE TEST
WASHING MACHINES
WATER SOFTENERS

More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic


• 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 to Septic Systems - what to do when buying a home with a septic tank
• Cesspools Home Buyer's or Owner's Advice
• 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?
• Drywells Home Buyer's or Owner's Advice
• 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
• Septic Systems Inspection, Testing, & Maintenance Book - online textbook: how to inspect, maintain, repair septics
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• 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.
• What is a Septic System An Engineer's View & Septic System FAQ's

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