a home photo lab - lots of photo chemicals into the septic system might be a problem at this propertyHow Does use of a home Washing Machine Affect the Septic Tank?

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Clothes washing machines vs. the 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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Homeowner's Guide to WASHING MACHINES Draining into Septic Systems

washing machine and various household chemicals and cleanersDoes 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 system or drywell.

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

The volume of detergent from a residential 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 laundry detergents or soaps should we use in a Clothes Washing Machine connected to a septic tank or to a Graywater System?

washing machine and various household chemicals and cleaners

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.

Dishwasher & laundry detergents: are discussed in detail separately at DETERGENTS in our article at DISHWASHERS vs SEPTICS where we discuss recommended detergents and also the effects of phosphates & detergents on the environment.

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

Apartment building washing machine room (C) Daniel Friedman

A private septic system tank and drainfield can be protected from clogging due to excessive use of detergents.

And even if a building's wastewater is carried to a public sewer there may be concerns with detergent clogging in the drain system. In the laundry room serving a residential apartment building such as shown in our photo (left, Bronx, NY), asking residents to follow these suggestions can help prevent sewer drain clogging.

  • 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 drainage or drainfield clogging.
  • High phosphate laundry detergents may be a factor in reducing drainfield life [more data is needed on this point.]
  • Liquid detergents recommended: 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.

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

photo of a graywater filter for septic systems
  • 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. Details are at FILTERS SEPTIC & GREYWATER
  • 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.

Also see CHEMICALS & CLEANERS into the SEPTIC TANK? & CHEMICALS, KEEP OUT OF SEPTICS-2 - separate articles

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