Cat litter should never be flushed down the drain (C) Daniel Friedman Toilet Don't Flush FAQs
Questions & answers about what can be flushed down building drains & into a septic system

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Toilet do not flush list questions & answers:

This article answers common questions about what's ok to flush or not flush down building drains.

This article series explains what items and chemicals are safe and what items are not safe to flush down the toilet and into a private septic system? What may damage the septic tank or leach fields? This document explains how to extend the life of the septic system by being careful about what goes into it.

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Questions & Answers about Flushing Stuff into the Toilet & Drain or Septic System

Toilet tank flush cleaners & deodorizers (C) Daniel Friedman

These questions & answers about what should or should not be flushed down building drains or into toilets and septic systems were posted originally at


Reader Question: Are toilet tank cleaners that clean with every flush bad for the septic system?

How about those toilet tank cleaners that clean with every flush, especially with bleach.

I have a septic system 4 years old now, and since day one i use blue bowel flush cleaners with bleach.

This year for the first time i noticed there is no grass on leach field. Is this my problem and should i stop using toilet tank flush cleaners. Please advise. Thanks - Dave A 4/21/11

Reply: Content, properties, & uses of some common toilet tank cleaners, deodorizers, & treatments


The amount of bleach from a typical toilet tank solid cleaner-insert cake in normal usage should not produce enough bleach in the septic tank to have a noticeable effect on the tank bacteria.

We found that toilet tank deodorant or "cleaner" product ingredients varied by product; some of the typical ingredients listed (not all of these are present in every product) included:

Toilet tank flush cleaners & deodorizers (C) Daniel FriedmanWatch out: most of the toilet tank deodorizer and treatment tablets and products we surveyed (October 2012) include

Watch out: I found in testing about 15 years ago that some toilet tank treatments caused the flush valve to deteriorate, resulting in running toilets that did flood the drainfield.

There is research on the effects of treatments for RV holding tanks and septic systems (a concern for those emptying an RV wastewater holding tank into a residential septic tank) and for toilet and toilet tank deodorants:

I will post some citations above at Chemical Contaminants Found in Residential Wastewater & Their Sources

Question: flushing toys into drains or septic systems?

can you flush toys? - Deepesh

Reply: of course not

No deepesh, I can't imagine any toy that can safely be flushed down a toilet. For example, plastics won't biodegrade in the septic tank and any toys flushed down a drain risk clogging piping. At TOILETS, DON'T FLUSH LIST you will find a more complete list of stuff to keep out of toilets, drains, and septic tanks or sewers.

Question: how much water would be "too much" water to be flushed into a septic system

"Water in large quantities"

What would be a "large quantity"?
1 gallon? 2 gallons? Swimming pool? - Tim

Reply: Water volumes that exceed the design load for septic system - x gallons/day


About "how much water is too much for a septic system to handle?", let's be reasonable. Posed by your question, a gallon of water would hardly be a "large" quantity since that's less than some toilet flushes. And a bath tub or shower use typically consume 30-50 gallons of water. A typical home septic system is designed to accept a daily wastewater load of 100-200 gallons per person in a household.

What can flood a septic drainfield and/or even damage a septic effluent dosing system are water volumes that exceed the anticipated daily design load. Examples of "large quantities of water" that damage septic system are most often found where equipment is malfunctioning:

- a water softener stuck in "regen" cycle can pump water continuously into the septic system, hundreds of gallons a day added to the normal load

- leaky toilets and other fixtures might, depending on flow rate, also flood the system

- putting together a local laundromat and connecting it to a typical residential septic system would flood and overload the system

- failing to keep groundwater away from the septic tank or drainfield flood the system and lead to its failure.

About a swimming pool, I'm doubtful that anyone would try emptying a swimming pool into a septic system, but indeed, I have seen failed drainfields that were saturated when a homeowner repeatedly emptied pool filter backwash waters and annual swimming pool drain-out waters directly onto the septic drainfield or soakaway bed.

Thanks for asking - these are important clarifications.

Question: What's the difference between "never flush" and "better not flush" categories of building drain and septic system care warnings?

Why are some of these items "never" and others "better not". I don't understand the distinction?

Also, why did deepesh ask about flushing toys down the toilet? Deepesh, do you really have no other way of disposing of them?

- Randy

Reply: Definition of "never flush" and "better not flush" drain dumping and septic system protection categories

Randy: good question. Thanks for asking for this clarification on the difference between NEVER FLUSH and BETTER NOT FLUSH things into a septic tank.

What's in the "Never-Flush-into-Septic" category?

Having researched various expert sources on septic tank and system care as well as having investigated septic system failures, in my OPINION some materials are very harmful and likely to cause costly damage if flushed down drains and into septic tanks and drainfields, while others may also contaminate groundwater, nearby wells, and the environment. Those items go into the NEVER FLUSH INTO SEPTICS category of things to keep out of drains and septic systems.

What's in the "Better-Not-to-Flush-into-Septic" category?

Other items, like cigarette butts, do not biodegrade in the septic tank, and can possibly contribute mass to a clog or blockage in a drain, but their individual size and anticipated plausible volume of occurrence in a septic tank is so small as unlikely to actually damage the tank. Rather they add non-biodegradable mass that has to be removed when the tank is pumped.

These are a bad idea - they risk remaining in the waste chain, even being spread in sludge on a field somewhere where they still don't biodegrade - but as their probability of causing rapid or expensive damage to the septic system is much less or even nil, I put these into the BETTER NOT TO FLUSH category.

At TOILETS, DON'T FLUSH LIST our summary page for this topic, and among the links listed at the "More Reading" links at the bottom of this article under that heading, you'll see a series of articles that explain the hazards of dumping or spilling various materials into drains and into septic systems.


Is bleach from a washing machine safe for a septic system? How much? - Alan 10/5/12



Bleach used at normal levels in a home laundry system should be so dilute in the septic tank as not to cause a problem. Follow the manufacturer's instructions;

Watch out: I would agree that dumping bleach wholesale into building drains for any reason is not a good idea and could damage the septic system.

In fact in a separate article on cheating on water quality testing, we report observations including by Steve Vermilye (dec). that property owners who had sanitized a well with high doses of bleach right before a building inspection put enough bleach into the water supply that we could observe the septic dye test colorizing dye fading from red to clear as the dyed water entered the septic tank.

Question: septic tank pranks with coffee?

(Mar 30, 2013) Andres said:
Can you put already made coffee into the septic tank? trying to do a prank.



Liquid coffee at any normal quantity brewed in a home won't hurt the septic tank.

Question: ok to use laundry detergent to unclog drains?

(June 17, 2014) Susan Marie said:
Can I use liquid laundry detergent to unclog bath drains? When Drano fail to unclog I pour liquid detergent down a clogged sink and it worked - unclogged the drain to flow easily. Are there any risks?



Liquid laundry detergent is not likely to be effective as a drain de-clogger. Perhaps there was a delay in the effectiveness of the Drano de-clogger or perhaps it reacted more effectively against a clog when the detergent (perhaps with additional water) gave more volume to the solution.

I don't see a particular risk as long as you are not overdosing a septic tank with de-cloggers or with detergents.

Question: improving the smell of flushed something or other

(June 17, 2014) Royston Watkins said:
Is there a product that will improve the smell of a foss when flushed?


Royston I don't know what a "foss" is.

In my experience additives and cleaners don't produce a lasting effect on drain system odors nearly so much as correcting venting defects or leaks.

Question: does milk harm septic tanks?

(Nov 28, 2014) Anonymous said:
Can milk into the sept tank, and will do any harm.



No not at normal household disposal levels.

Question: ok to flush hair into the septic system? From a dog kennel or a beauty parlor?

7 March 2015 ArticTraveler said:
Can you clog up a leach field with hair from a kennel and or human hair from a Barber/Beauty shop? Should it go through it's own septic system prior to going into the primary (household) and/or secondary leach field?



I think I'd have to say no and yes.

First: if the septic tank is working properly, baffles in the tank, especially the outlet tee, should prevent solids, including floating solids like hair, from exiting the tank and clogging the drainfield. If that's the case, then the volume of hair in the tank would not normally be significant and it'd be emptied at the next scheduled pumpout.

If large volumes of air are entering the building drain system I'd agree that there are drain clog risks, and if that hairy mess, say from a dog kennel or grooming center or a barbershop were entering the septic tank, at the next tank pumpout an inspection of the scum and sludge thickness levels should tell us if more frequent cleaning is needed.

Finally, rather than installing a different drainfield or septic system (very expensive), if you want to minimize the risk of hair clogging in the system, I'd install a septic filter at the tank outlet. That will add a regular maintenance task, perhaps monthly for a kennel, but it'd protect the drainfield.

On 2017-10-24 by (mod) - OK to flush Polident denture cleanser down the drain and into a septic system?


The manufacturer's MSDS for Polident Denture Cleaner [PDF] (Glaxo Smith Kline) in addressing "accidental release" advises

Prevent entry into waterways, sewer, basements or confined areas.

But I think that has to pertain to industrial settings such as where the product is manufactured. It cannot, in any sensible view, mean that spilling out a cup of denture cleansing liquid into the local drain and thence into a septic system can be harmful. By sensible view I consider the following:

The quantity of Polident denture whitening products in normal household use is so tiny compared with the volume of a septic tank as to make it so dilute in the septic system as to be harmless

The principal ingredients are rather mild - sodium bicarbonate (baking soda, 30-40%), citric acid (think lemon juice <= 20%), and similar whitening constituents along with a trace level of peppermint oil.

there are, therefore, warnings on the polident msds from glaxo smith kline that the product can be toxic if eaten or harmful if gotten in the eyes. >

On 2017-10-24 by Ann

Will a polident solution harm the septic tank?

On 2017-09-01 by (mod) - Will liquor hurt the septic tank

That would depend on the quantity of alcohol being disposed of into the septic system.

At nor mal private household usage levels, no.

On 2017-08-30 by Linda

Will liquor hurt the septic tank

On 2017-07-18 by (mod) - flush down a mold infested food item that may help in the break down of buldge in the septic tank?

Sorry but thst won't fix a septic tank sludge problem. Have the tank pumped, cleaned, & inspected.

On 2017-07-17 by will

Can I flush down a mold infested food item that may help in the break down of buldge in my septic tank. My dad (deceased) talked about flushing down moldy liver which would assist in the break down in the tank.

On 2017-06-21 by (mod) - can Vitamin D3 -4000iu harm septic tanks?

Unless you are describing washing large quantities of a vitamin E oil into a septic system, such as vitamin D fabrication plant, no, it's unlikely that individual use levels or household use of us have a vitamin would be measurable in a septic system.

Nursing homes and hospitals on private septic systems do need to be concerned about the larger volume of medical substances flushed down drains, particularly antibiotics.

On 2017-06-21 by rich

can Vitamin D3 -4000iu harm septic tanks?

On 2017-06-06 by (mod) - safe to flush the liquid contents of DampRid down the toilet ? NO!

THanks for asking, Ruth.

DampRid, produced by W.M. Barr in Memphis, is an anhydrous calcium chloride product that consists of three salts: calcium chloride (CaCl), sodium chloride (NaCl), and potassium chloride (KCl). These salts in a container are used to absorb moisture from the surrounding air.

This is classified by OSHA as a hazardous material, according to the company's product MSDS provided by a vendor, Home Depot, at

You should not put the material directly into water nor put water directly into the material.

On 2017-06-06 by Ruth

Is it safe to flush the liquid contents of DampRid down the toilet that is connected to a septic system?

On 2017-05-06 by (mod) - many toilet papers do not completely break down into microscopic particles in the septic tank

Our lab tests (given here at have shown that many toilet papers do not completely break down into microscopic particles in the septic tank.

The rate of breakdown depends in part on the amount of agitation in the septic tank and of course on the composition of the paper.

However the dominant factor seems to be the volume of paper flushed into the septic tank. I wouldn't worry about it as long as your septic tank has intact baffles to prevent solids from flowing out of the tank.

On 2017-05-06 by Anonymous

Why does myseptic tank not desinegrate toilet paper

On 2017-05-01 by Laura

I bought pool salt and have put some in toilet and flushed will it stop my lines up?

On 2016-12-05 by (mod) - stop green growth in rainwater cistern used to flush toilets

You could perhaps best proceed by having the water tested to see what's growing in it - most likely it's an algae. An algecide or probably even a dilute bleach solution might be enough to stop the growth.

On 2016-12-05 by Mazza

We have a tank which gathers rainwater which we use for flushing the toilet.

However sometimes it turns green which is not only unsightly in the toilet, but also puts a nasty lining around the bowl. Is there something that we can put into the tank to keep the water clear, which would not harm the septic tank?

On 2016-07-10 by (mod) - water softener impact on septic


Many homes discharge water softener backwash into the septic tank (and thus into the drainfield or soakbed). You MIGHT be ok with that appraoch, but there are two risks:

1. salt can damage the drainfield and shorten its life.

2. extra water discharge into the system can flood the drainfield and stop it from working - more of a problem if your softener gets stuck in "regen" mode or if it has to run with high frequency.

A better approach is to direct softener drainage into a drywell for separate disposal.

Search Inspectapedia for WATER SOFTENER IMPACT on SEPTIC to read complete details of this topic.

On 2016-07-10 by frank williams

will it hurt my septic tank to let the water from a water softener go to the septic tank? email address is thank you

On 2016-06-14 by (mod) match septic service to wastewater volume?

Let's separate wastewater volume from wastewater solids, Jimmie.

An increase in solid waste, sewage, garbage grinder waste, would mean that a septic tank needs to be cleaned or pumped out more often. Search InspectgApedia for SEPTIC TANK PUMPING SCHEDULE to see details.

An increase in wastewater volume caused by long showers or running toilets would have two different effects from the above:

1. there is a serious risk of flooding the drainfield, preventing proper treatment of discharged effluent in the soil, and leading to a costly septic soakbed replacement. Pumping the septic tank more often will have absoltuely no effect on this problem.

2. there is a possible risk of abnormal levels of agitation of solids in the septic tank due to high wastewater flow volume compared with septic tank volume that could in turn give inadequate settling time to settle out solids and grease.

IF the septic tank baffles are damaged OR if there is significant agitation in a tank that is undersized for the daily wastewater flow, THEN there is increased risk of discharge of small waste particles out of the septic tank and into the absorption system - thus shortening its life by clogging the soil more rapidly than happens normally.

Search InspectApedia for SEPTIC TANK SIZE to read details.
also if you like
Search InspectApedia for SEPTIC TANK EFFLUENT RETENTION TIME to read details about that concern.

On 2016-06-14 by JIMMIE C. DE VANE

Is there a concern that frequent flushing, longer than normal baths, showers, frequency of clothing washer, and dishwasher usage cause increase need to Service / Flush Septic System?
For example, a four bedroom home occupied by two people have pumped out the Septic System Bi annually and sometimes longer spans, for decades.
Household occupancy increased to five adults in the four bedroom home for the last 30 months.

Main Question:
Septic System serviced / pumped out by tanker truck, in last twelve (12) months. Another Sceptic system service provider reported one tank filled to capacity, and sludge / effuse requires immediate pumping service (Friday, June 17, 2016)!
Increased Volume of water usage likely cause of need to shift from biannual pumping to annual service calls?
Other causes possible?
Incomplete pumping service?
Or input into system of chemicals sited?
Your advice on chemicals to avoid, suitable flushable toilet tissue, solids such as small toys and machine (select)chemical discharges from cloth washers, and some dishwasher chemicals may challenge bacterial management, and or aggregate environment pollutants into the soil.
And / Or?

Would excess water usage cause increased frequency flush cycles?
Can increased water usage by 3 adults from two occupants be cause attentuation and shorter need to pump cycles?

On 2015-09-28 by mychaela maine

Will hair dye ruin the trailer showers and septic tanks?

On 2015-08-05 by Andy

If the septic system is working right, the water level is up high (at the bottom of the outlet) which means when you flush toilet paper it is trapped in the baffle at the top of the water surface.

The baffle is supposed to help stop the scum from backing up the inlet but if the toilet paper is trapped in the baffle then as more paper gets flushed it is still going to block the inlet; or should the force of the water coming into the inlet push the paper down and out of the baffle? Thanks.

On 2015-07-09 21:41:45.709490 by (mod)

Super, Frank. Maybe I should add "THIS LIST" to the things we hope people won't flush down the john.

If you have other list suggestions let me know.


On 2015-07-09 by FRANK FITZGERALD


On 2015-07-08 by Mike

Can I use sodium lauryl ether sulfate based toilet cleaners in a septic tank system?

On 2015-06-14 by (mod) don't wash masonry mortar into the septic tank

I would not wash mortar residue into a septic system. The substance is highly alkaline and may be harmful.

On 2015-06-14 by Ann

Have recently had my house reruffcasted and was wondering if its ok to power wash the mortar residue into my septic tank


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