Sunday, October 2, 2022


Dump your holding tanks in your home septic system?

We often see RVers give advice that dumping holding tanks at home is not a problem – even into septic systems, rather than a city sewer system. Here are a couple of points to keep in mind:

Home systems are generally tasked to handle a relatively low flow of sewage over a period of hours. Dumping a large amount of RV waste at once could lead to disturbing the layer of sludge in a home septic tank – possibly causing it to break up and move out into the leach field. That can lead to an expensive clogged system. If you have both full black and gray water tanks, it might be best to dump one at a time, spacing the dumping out over a couple of days. on

On another note, here’s a comment from the U.S. Environmental Protection Agency. “When chemicals, such as formaldehyde, are added to septic systems, they can cause bacteria in the system to die. When this happens, the septic system cannot treat waste adequately. Solids that are allowed to pass from the septic tank, due to inadequate or incomplete treatment, may clog the leach field. Furthermore, clogged systems may send inadequately or incompletely treated sewage to the surface, threatening the health of people or pets who come into contact with it. Or it may percolate to groundwater, where the chemicals and untreated wastewater could contaminate nearby drinking water wells, rivers and streams. Please read labels carefully to identify any hazardous ingredients.”

What constitutes “hazardous ingredients”? Formaldehyde: an active ingredient in some
deodorizers, also called Formalin. Formaldehyde is an EPA-recognized probable carcinogen (i.e., causes cancer). Paradichlorobenzene: Known carcinogen and drinking water contaminant. A common ingredient in mothballs, urinal cakes and bowl fresheners.

One more thing: Should you decide to “build your own” dump station at home, BE SURE your dump port is installed between your home and the septic tank. Don’t be like the RVer in Washington state who put his between the septic tank and drain field. He learned a very expensive lesson!


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BILLY Bob Thronton
7 months ago

Heres an idea, if your concerned about things going awry.

Since the frequency of an RV dump (at home) episode is extremely low, obtain a plastic barrel (food grade not necessary), drill multiple holes in the lower third, then dig a hole, place stone in the bottom and around the sides up to the holes. Attach a PVC pipe, through the lid with stainless steel screws to grade level (with a cap) and your done.

7 months ago

This sounds like a health dept’s nightmare! Located close to a well? close to a stream? under your bedroom window? Do not invite me to your BBQ.

BILLY Bob Thronton
7 months ago
Reply to  Larry

Oh Larry, now who would do something so stupid as that. A couple of things;

First, if your not that bright (general speak) then you should not ever think outside the envelope.

Second, all ground water is, well just that ground water. So, to explain it would be redundant. Ever wonder where regular effluent goes from said leach fields, yep you guessed it, ground water. You see Larry, the ground is a beautiful thing, it cleans the impurities as it migrates deeper into the ground water. So much so, that wells, in some parts of this great country are on avg., two hundred feet deep. That my boy is a lot of clean goin’ on. And of course you wouldnt put it near your water source, unless your Cousin Eddy!

And, I’ll invite you to my next BBQ, but bring bottled water if it gives you the heebee geebees.

Earnie W
7 months ago

I have a filter on the exit pipe of my septic system that keeps solids out of the leach field. I have not had any issues dumping my RV tanks into my dump station that connects to the inlet pipe.

Steve Hericks
7 months ago

The fear mongering is palpable….just throw out some chemical names and the scene is set.. ‘Formaldehyde is a gas that is dissolved in water to form the compound formalin. Formalin is the saturated solution of formaldehyde in water. A 100% formalin solution is equivalent to 37%–40% formaldehyde.’

‘commonly used as an industrial disinfectant, and as a preservative in funeral homes and medical labs. It can also be used as a preservative in some foods and in products, such as antiseptics, medicines, and cosmetics.’

Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to formic acid, so it does not accumulate in the body.

BILLY Bob Thronton
7 months ago
Reply to  Steve Hericks

And the truth shall set you free!!

I remember way back, Boones’ Farm wine (apricot splash) contained formaldehyde, didnt hurt me none. Maybe a couple guardrails. Good reply Steve.

7 months ago

BBT, you need to be evaluated…..professionally.

BILLY Bob Thronton
7 months ago
Reply to  Larry

Can you suggest who you go too?

Thomas D
7 months ago

I’ve dumped in our whenever the need arose for 35 years without a problem. I don’t use anything in the toilets to kill bacteria and anyway,we are required to pump the septic tank every 2years. I don’t believe that dumping in about 75 gallons of waste water is worse than dumping up to 100 gallons of whirlpool tub water. BTW I use a macerator to dump.

7 months ago

Many years ago I used to dump into our septic tank. While we never had an issue, I did decide that it might not be a good practice to load so much in at one time and stopped.

Chris Mead
7 months ago

I dump into mine too. No issues. With the black, I dump and flush. I also empty my septic tank every 4-5 years.

Anthony King
7 months ago

I’ve been dumping into our Septic System for over 35 years or so. The Toilet Chemicals are safe for your system and they haven’t used Formaldehyde in ages. Right now at my house I use a Sewer Solution and about 80’ of 1” PVC to dump into the 2” Cleanup on the back of my house. I’ve had zero problems over the years.

7 months ago

Very interesting article. We have toyed with the idea of adding a port to our septic tank. Lots to think about. Thank you.

The Lazy Q
7 months ago

I don’t trust the alphabet agencies. And since California thus the rest of the states follow bans pretty much anything that is of good use to help us owners out, I doubt we will see a problem. In the event my septic goes full, well then, I will get it emptied. And I don’t think dumping after an occasional boondock that my little 40 gallon rv tank will be a flow problem. Matter of fact been doing this for four years now.

Tommy Molnar
7 months ago

Many way out RV parks have septic systems. I wonder how they manage.

7 months ago
Reply to  Tommy Molnar

It’s all about engineering and design. The best advice in the article is to low dose your home system and not dump everything at once. At my house the gray water waters the grass. The black goes to the septic system in increments.

7 months ago
Reply to  steve

I like the grey water idea.

7 months ago

Thanks! We installed a separate 800 gallon septic tank, just for our RV, in our pasture. I’ll be sure we never use toxic chemicals in it!

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