What chemicals are bad for septic systems? Here is a list of dangerous septic tank chemicals to avoid to keep your system working fine for a very long time.

A septic tank is an underground on-site sewage chamber commonly made of concrete, used to hold household wastewater for a certain period, usually 2-3 years.

The purpose of a septic tank is to separate solids from liquids in the wastewater, which comes from all sources in the house. They include sinks, baths, toilets, showers, washing machines, and dishwashers.

The size of a septic tank depends on the number of bedrooms.

In case of a backup, septic tank chemicals are used.

Fact Check:

What Are Septic Tank Chemicals?

Septic tank chemicals are chemicals that are either acids or bases used to unclog pipes or in cases back up. These chemicals can also be used on a new system or after repairing an old one.

Recent studies show that there are a lot of useful chemicals and also bad ones, well, they are not so bad, but should never be used as routine maintenance.

Chemicals used in septic tanks usually consist of inorganic compounds, organic solvents, and Biological chemicals.

Uses of Septic Tank Chemicals

Generally, septic tank chemicals are used for the following;

  • Unclogging of pipes
  • Prevent backups that make the house inhabitable
  • Aid easy pumping out of wastewater by the prevent contamination of vacuum truck
  • Biological chemicals also help to break down the solid waste but should be used sparingly, just not to destroy the natural breakdown process.
  • These chemicals also help to adjust the chemical balance so that the tank can function properly

Effects of harmful septic tank chemicals

  • Underground water pollution
  • Destruction of useful septic bacteria, thereby causing clogs that lead to back up
  • Causes Bad odor in the environment
  • The oil-based ones can coat the solid waste making it challenging to break down, for example, bath oils
  • There is a high chance that the chemical will ruin aquatic life if it is located near such a habitat
  • Food poisoning

Septic Tank Chemicals to Avoid


In several other wastewater treatment systems, the system operates by preparing the sewage water to be collected on-site.

The concern comes where this device is employed in a hospital or nursing home; the volume of antibiotics they have poured into the septic tank cannot be handled properly, so the septic tank will have to destroy the bacteria.

Nevertheless, the tiny volume of medication that arrives from someone who uses the antibiotic and spills it from the sweat should not be included in the septic tank at all.

Therefore, it is better to isolate antibiotic waste from other waste.


According to the US EPA, for contaminants to be eliminated in septic tanks, the amount of chlorine required to clean approved drainage effluent varies from 5 to 20 mg / L. Utilization above this amount of chlorine can destroy septic bacteria and flood the septic tank network with wastewater.

A significant volume of chlorine in the septic tank may generate chlorine gas and damage the human respiratory tract, the eyes, and the skin.

To prevent this adverse impact, please always use chlorine tablets under the recommended concentration, and the Occupational Protection and Health Administration has set the appropriate exposure level for elemental chlorine at 1 ppm or 3 mg / m3 in the United States.


There are many dangerous organic compounds in the pesticide, such as DDT, DDE, DDD, Metam sodium, Carbamate, and so much more that can kill and trigger human deaths. Pesticide flowing into the septic tank would be combined with groundwater, which can kill people.

The best way to stop this negative outcome is not to pump the pesticide into the septic tank.


At all costs, you must try to avoid the temptation of flushing this chemical into your toilet; worse still is the act of dumping it into a septic tank. Gasoline can be detrimental to the ecosystem because it disrupts the balance of soil nutrients.

With this disruption, likely, plants will no longer thrive in that area, or worse, will kill an existing plant. And it would be a smart move if you would not spill the dangerous chemical into the toilet to cause adverse consequences.


With the chemical formula (PO3−4), Phosphate is often used as a cleaning agent.

Some Detergent manufacturers use Phosphate as one of the components in producing detergents. It has been proven that Phosphate could cause diseases to humans if it is ingested in significant quantities.

The act of spilling this sort of chemical into your septic tank water treatment system would not be a smart move. This is because it may be combined with the water you drink.

When you have Phosphate on your septic tank network, it may be controlled by the following;

  • treatment of raw/primary wastewater,
  • treatment of final effluent of biological plants (post-precipitation),
  • Treatment of secondary biologic reactions (co-precipitation).

Some phosphate compounds have been forbidden from the international trade market because it has been marked as a hazardous chemical compound restricted for sale.

Magnesium Sulfate

This chemical is primarily used in the manufacturing of toiletries, also known as Epsom salt.

Although it has been deemed safe for use when used at a small amount; however, when used in a large quantity, this form of a chemical may trigger many illnesses of human health. This could go as far as causing problems with the kidneys.

It is also strongly advised to use this chemical in a small quantity and to drain it in a small quantity in the septic tank in the same amount as the bath soak.

Hydrochloric Acid HCL

Many plumbers use this chemical to solve clogging problems.

The chemical, in some cases, does free the pump; however, also Hydrochloric acid HCL is counted for a strong acid and could produce gas from it.

It has been found that using a strong chemical is not recommended because of the harmful effect it could bring, the harm of Hydrochloric acid HCL includes; damage in respiratory organs, eyes, skin, and intestines irreversibly.

Simply substitute any strong acid to be poured into your septic system. It is better and safer to make use of an organic chemical to solve any clogging Challenge.

Caring for Your Septic Tank Without Using Chemicals

  • Check your system and keep correct documentation; check your system periodically for proper management and arrange your system’s documents (diagram, machine repair, etc.).
  • Filter your septic tank frequently; the general practice is to filter the septic tank every one or three years to guarantee that the solids are adequately broken down so that the drain field is not clogged. Routine pumping will help avoid system failure and increasing the reliability of the machine.
  • Do not use excess volumes of household chemicals; you may use regular quantities of household detergents, bleach, drain cleaners, and other household chemicals without preventing the bacterial activity in the septic tank. Ensure that you don’t pour cleaning water meant for plastic paintbrushes and cans in the house sewer.
  • Stop dumping grease into the drain. It will block the sewage pipes or build up in the septic tank and obstruct the inlet. Keep the waste grease jar apart and throw it away with the trash.

Household chemicals to Avoid in Septic Tanks

You may think that household items have nothing to do with backups, but they do. They cause 75% of the damage done.

LIST: Soaps & Shampoos That Are Septic-Safe

Below are examples of what to avoid.

  • Septic tank additives e.g., yeast
  • Gasoline
  • Bath oils
  • Photo chemicals
  • Cooking grease
  • Cat litter
  • Garbage disposal
  • Cigarette stumps
  • Sanitary pads or tampons
  • Plastics
  • Paper towels
  • Coffee grounds

Best Chemicals To Use on Septic Tanks

The following are safe chemicals to use on septic tanks, they include;

Guidelines in the Selection of Products to Use

  • Note that septic tanks do not differentiate between toxic substances and chemical substances, so it is advisable to prevent the addition of harmful chemicals to the environment, biological products are recommended
  • Use only natural products that are made with ingredients that can be broken down in the environment, that’s safer compared to products that contain chemicals that cause a build-up
  • Ensure that whatever product you wish to pass through your septic system has been certified safe by a health agency. This way, you are sure not to contaminate the environment and yourself.
  • Whenever you buy products that contain chemicals, be sure to check for harmful substances in the ingredients section, to be sure no harmful substance is enlisted. This will also save you future troubles.


As humans, we are responsible for any damage caused to/in our environment.

In the case of wastewater, our health would be at risk if we don’t monitor what we send into our septic system, and we may end up creating health challenges for ourselves.

Developing the habit of doing what is right always will pay off in the long haul.

One Comment

  1. Epson Salt? Good or bad? Shows up on both lists.

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