Thetford PortaPotti chemical toilet Chemical Toilets - when can we empty a chemical toilet or RV holding tank into a Septic Tank?
     


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This RV and chemical toilet article describes acceptable ways to empty a chemical toilet, porta-potty, or RV waste holding tank, and answers the question of when these can be emptied into a residential septic tank. Chemical toilets with larger waste reservoirs are used in RV's and campers as well as for full-sized portable toilets or Porta-Johns used at construction sites and at outdoor festivals.

Other common portable toilets include models from Sears, the Coleman, and Reliance toilets who provide a hassock model portable chemical toilet. Our page top photo shows a chemical toilet set atop a septic tank service riser. The chemical toilet's holding tank has been removed so that the toilet empties directly into the septic tank - a perfectly functional emergency toilet setup, but unstable and of course lacking in privacy.

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Is it Acceptable to Ever Dump an RV Holding Tank or Toilet into a Home Septic System Tank?

Chemical toilet being emptied into a septic tank (C) Daniel FriedmanWe would not hesitate to occasionally dump a portajohn or small, portable, chemical toilet into a home septic tank - the volumes are so low, typically two gallons or so total, that the deodorants or disinfectants in that small container would be so dilute as not to harm the tank bacteria.

[Click to enlarge any image]

But not only in view of the typical state standard on dumping chemical toilets into the environment, but further and more serious, an RV is a different matter as the holding tank is much bigger. It depends on what chemicals you're using in your RV holding tank.

I'd contact the manufacturer and ask for their literature on this point - if you get something from the manufacturer of your product, pass it on to me.

Here's one example of one manufacturer's comment about dumping RV chemicals into a septic:: "Yes [you can empty your RV holding tank into your septic system], as long as your septic system is fully functioning, adequately sized and properly maintained. If you do, it's important to use only the recommended amount of deodorant in your holding tank and only empty when the tank is full.

Also, because holding tank waste is very concentrated and breakdown takes longer, we recommend you dump only one RV holding tank in a home septic system per week." --Copyright © 2010 Thetford Corporation.

How Much Holding Tank Deodorant Chemical to Use

Coleman chemical toilet deodorant disinfectant (C) Daniel Friedman

Watch out: don't overdose a small portapotty or chemical toilet with too much RV toilet or RV holding tank deodorant or disinfectant. A typical Coleman™ chemical toilet packet contains enough dry powder to treat a 40-gallon chemical toilet holding tank, such as that found on an RV.

Coleman's portable toilet instruction manual includes advice on using a holding tank deodorant. The toilet instruction manual suggests adding one 2-oz dry powder packet with one pint of water. But that's to treat 40 gallons of waste. If your portapotty only holds a few gallons, perhaps 4 gallons, you can use much less.

A Thetford Aqua Kem™ liquid bottle also contains treatment sufficient for an RV tank. But the little chemical toilet holding tank we show above holds just about two to three gallons of waste. You would want to use about one tenth of the package or container of holding tank deodorant in a little tank like this one.

If you use too much disinfectant it won't damage the toilet, but if you intend to empty your little toilet into a residential septic tank, you don't want to insert more disinfectant or deodorant into the septic tank than is necessary.

These products and their package sizes are intended for RV or marine (boat) septic holding tank use.

Watch out: dumping a chemical toilet or RV waste holding tank into a septic tank might create a problem if users of the chemical or RV toilet are taking antibiotics or other bacteria-killing medicines. See DISABLED or ELDERLY-USE TOILETS for details.

Biodegradable RV Toilet & Holding Tank Fluids?

Aqua Kem Thetford Holding Tank Deoldorant (C) Daniel Friedman

The product literature for some septic holding tank additive and toilet cleaner manufacturers such as Elsan's Organic Toilet Fluid - UK informs us that their products are harmless, biodegradable, and acceptable to empty into septic tanks, drainfields, reed beds, etc. We are researching the topic and will report here.

Thetford Corporation's product literature informs us that their Aqua-Kem products are "100% biodegradable liquid and environmentally safe when disposed of properly." We are researching the topic and will report here.

Note that Thetford also informs us that
WARNING: This product contains a chemical known to the State of California to cause cancer.

Marykate Heads Up MKT-4532 is another RV holding tank deodorant with a detergent base and intended for use in marine or RV holding tanks, recirculating and portable toilets. The company specifes that the pproduct has a
"Non-toxic and non-formaldehyde formulation"

Note that the Marykate Heads Up RV & Marine holding tank deodorant label includes some safety warnings that we could not quite read
"Caution: may be harmful if swallowed, may cause eye irritation"
and other text that we could not read - readers who have one of these bottles and can send us the text are welcome to CONTACT us with that information. Marykate products appear to be produced by CRC Industries, Inc.

Also see Septic & Holding/RV Tank/Toilet Chemicals MSDS

Calculations and Data to Evaluate the Effect of Dumping RV Holding Tanks Into a Septic Tank

RV dumping station sign,  Whangamata, New Zealand (C) Daniel FriedmanComment-DF: What's missing from this is a more scholarly explanation that includes real data such as:

  • the size of the RV tank in gallons
  • the concentration of and chemistry of the disinfectant/deodorant agent used in the RV tank
  • the size of the septic tank in gallons
  • the daily wastewater flow other than from the RV dumping that will be available to dilute the RV chemicals
  • the concentration of the RV disinfectant chemicals in the septic tank
  • the type of septic system - some systems, mound, recirculating sand bed, aerobic, or onsite wastewater treatment mini plants, may have widely varying vulnerabilities to extra chemicals and disinfectants

Photo above: RV dumping station sign near Whangamata, New Zealand.

What are the problems if we empty an RV or other waste holding tank into the septic system?

The concern with dumping RV disinfectants or any chemical into a septic system is that high concentrations of a disinfectant may not only harm the natural bacterial and other actions that occur in the septic tank, worse, it could harm the biomat which forms under and is essential for proper functioning of the drainfield. With some chemicals there is also the risk that the chemical itself is an environmental contaminant. You can understand why New York State and perhaps other states have taken the position quoted just above.

Considering that the chemical manufacturer says they are confident that their chemical won't harm the system if we follow their instructions, then if you want to develop some real test data, after checking with your local health department to discuss doing a mini-study of this kind:

Go ahead and empty your RV tank into the septic system, Once only, making a note of the volume dumped and the other information listed above. If you don't already have one, install a riser port at the septic tank pumping opening so that you can use the same riser port as a dumping station. You'll just pull the cap off of the riser pipe and connect your RV dumping hose to it.

What else should we do to avoid Damaging the Septic System with our RV?

NOW: since you're putting sewage along with deodorant (which probably retards sewage breakdown) into the septic tank, and since we don't have any quantitative data from the manufacturer about how many RV gallons can go how often into a septic tank of any given size (I doubt they know), I would respond by moving up my septic tank pumping schedule to an earlier date.

A Proposed Septic Tank Pumping Schedules if We Empty an Recreational Vehicle Holding Tank into the Septic Tank

The below is ARBITRARY to use as a starting point -

RV gallons put into   Next septic tank Move your tank
tank in one year   pumpout was due  up sooner by

250 gals     1 year     2 months
500 gals     1 year     4 months

250 gals     2 years    0 months
500 gals     2 years    2 months

250 gals     3 years    0 months
500 gals     3 years    0 months
1000 gals    3 years    4 months

FOLLOWUP: IF, when you pump the septic tank+RV-waste and your pumper says that there was no unusually thick floating scum or settled sludge or suspended solid waste, you can begin to push the septic tank pumping schedule back out to the frequency given in my table.

If I can get some more accurate data I will amend this current table (which is completely made-up and speculative) and post it online.

Products - for Alternative Septic System Designs aerobic system pumps, media filters, gravelless systems, other advanced wastewater treatment products including waterless, low water, chemical, and incinerating toilets.

 

Continue reading at CHEMICAL TOILETS or select a topic from the More Reading links shown below.

Or see CAMPING & EMERGENCY USE TOILETS

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RV HOLDING TANK DUMP INTO SEPTIC TANK? at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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