For the five or 6 years that I have been RV'ing, for convenience, I would sometimes dump my tanks into my home septic system upon returning home. While I have felt pretty comfortable doing this, I have also wondered if there was any potential for damage (to my home septic system) from this practice. So, when the tanks were especially full, I would sometimes throttle the flow so as to only allow part of the tank(s) to dump at a time. Give it a moment or two to settle, then dump some more.Today, when I had my septic tank pumped (I do it every 5 years), I took the opportunity to raise this question with the pumper.I learned that IF chemicals are used in the RV holding tank AND this dumping is done frequently (i.e.; > 12 times per year), then over time, these chemicals will build up in the septic tank enough that they start to liquefy its contents. If the contents of the tank liquefy (they are supposed to separate; with solids at the bottom, water in the middle, and a scum layer on top), then this "slurry" makes its way past the outlet sanitary tee (located in the center of the tank and designed for only water to pass) and into the drain field. On the other hand, if this dumping only happens a few times per year (6 to 8), then it was his opinion that it "isn't likely" to cause a problem.When I told the pumper that I don't use chemicals at all, he responded that I "can dump as much, as fast, and as often as I want". The inlet tee will slow down the flow so as not to cause turbulence in the septic tank and the contents will be digested by the natural process in the tank (not liquefied as the RV chemicals "eventually" do). This made sense to me so I wanted to share it with the RV community. Happy dumping.

Hello, folks. Civil engineer here. I design wastewater systems.Conventional septic tanks are an anaerobic environment (i.e. "septic") in which breakdown of solids into soluble substances happens on a glacial speed (SLOW). Solids build up on the bottom and grease scum builds up in a layer on the surface. If you are a low loading user, it may take a LONG time for the solids and grease buildup to get to the point where the tank no longer effectively clarifies the septage before it exits the tank and heads for the leach field. In a properly functioning system, the clearest water is in the middle elevation of the tank where the outlet pipe is. But if that outlet starts receiving greases or solids, the leach field will be destroyed (clogged tight).NOT pumping your tank periodically until/unless there is a problem is similar in strategy to never topping off the oil on an old engine until the low pressure red light comes on on the dash. The damage is irreversible at that point.The guy who has never pumped his tank and grinds up everything leftover on his plates either has an unsafe leach field built in soils innately made of gravel or his field is totally locked up and the flows are getting out on the surface or in a cross connected drain tile (which you'd never see).My advice: Find out the dimensions of your tank and inspect it annually to make sure that the scum layer bottom and sediment layer top are at least a foot away from the opening to the outlet pipe (usually an elbow). Yuck. Or pay to pump it every couple of years and ask the honey wagon guy to measure for you before pumping. Increase pumping interval if its not building up much between pumpouts.

Every five years? Wow. I just had mine pumped after 24 years. Of course, there's only the two of us.I dump my tanks into my septic tank once a year upon getting home from our last trip. However, I usually only have just a small amount in it as I also dump at our last stop. I do use a macerator so that the flow into the tank is no where like the flow from a stinky slinky. I also do not use any chemicals except for laundry soap.We've been doing this for the past 15 years and have not experience any problem. We only had the septic tank pumped because we had a blockage on the main line from the house which didn't affect dumping the mh tanks into the clean out right next to the tank. Figured while we had the line dug up and replaced, might as well and have the tank pumped.Ron

For many many years I have dumped my black and Gray into the clean out of my septic and later the city sewer system. I also do not use chemicals of any kind. Nature takes care of that, if you do not dump tanks too often. I never had to have my septic cleaned, and the city sewer I did not worry about. I did ask the city sewer mgr about dumping into the city system, and his words to me; it does not care where the sewage came from, it is built to handle it.

My general instinct on the subject would agree that the "chemicals" used for keeping the holding tanks smelling rosy can't be beneficial for the processes that are taking place in a normal septic tank. And I never did understand the talk of overloading your tank with a dump from the RV. The tank & leachfield sizing is based on average flows, not peak flows.

Makes sense to me; the stuff that you dump from the RV, particularly if you don't use any tank treatments, is not any different than the stuff that goes from the house into the septic system.A household bathtub will often hold 50 or more gallons, by way of comparison, so dumping the tanks from many RVs would not put a lot more sewage into the system at once than would taking a nice deep bath. Of course, both bathtubs and RV holding tanks come in a variety of sizes.

Dumping RV tanks into home syptic system | Good Sam Community

Dutch_12078
Explorer II
Nov 07, 2015
I have no idea of the cost, but a neighbor near our Adirondack cottage had 200 foot of leach field replaced a couple of years ago. The contractor that did the job was in and out in three days, and when they left about the only way we could tell where they dug was by a slightly different color of the grass in those areas. A few weeks later, even that had blended in. The family had full use of the plumbing while the work was being done.
kenzmad
Explorer
Nov 08, 2015
Turtle n Peeps wrote:
kenzmad wrote:
manualman wrote:
Hello, folks. Civil engineer here. I design wastewater systems.

Conventional septic tanks are an anaerobic environment (i.e. "septic") in which breakdown of solids into soluble substances happens on a glacial speed (SLOW). Solids build up on the bottom and grease scum builds up in a layer on the surface. If you are a low loading user, it may take a LONG time for the solids and grease buildup to get to the point where the tank no longer effectively clarifies the septage before it exits the tank and heads for the leach field. In a properly functioning system, the clearest water is in the middle elevation of the tank where the outlet pipe is. But if that outlet starts receiving greases or solids, the leach field will be destroyed (clogged tight).

NOT pumping your tank periodically until/unless there is a problem is similar in strategy to never topping off the oil on an old engine until the low pressure red light comes on on the dash. The damage is irreversible at that point.

The guy who has never pumped his tank and grinds up everything leftover on his plates either has an unsafe leach field built in soils innately made of gravel or his field is totally locked up and the flows are getting out on the surface or in a cross connected drain tile (which you'd never see).

My advice: Find out the dimensions of your tank and inspect it annually to make sure that the scum layer bottom and sediment layer top are at least a foot away from the opening to the outlet pipe (usually an elbow). Yuck. Or pay to pump it every couple of years and ask the honey wagon guy to measure for you before pumping. Increase pumping interval if its not building up much between pumpouts.

As an owner of a septic tank cleaning company, I am happy to see someone chime in here who has a grasp on how the tanks work. This has been a hard topic to read, knowing all the money these misinformed people will be spending in the future.

Since you brought up money lets talk about that for a moment.

I have no idea what you charge where you live but many, many, many years ago it was $250.00 where I live. It's now $450.00 to pump a tank and has been there for many years.

I haven't pumped my tank for 40 years in one of my houses. Now lets go low and say the average was $250 to pump my tank over the years.

Now $250 a year times 40 years is $10,000 grand!! 10 GRAND! At the other house I saved $7,500!

So total I saved $17,500 dollars!

Now, I concede that in the future I "may" have to replace my leach field. I might even have to do it in my life time. Then again, maybe not? Nobody knows for sure, not even the experts.

I have access to a hoe, and gravel and pipe is cheap. For sure not over a couple of grand and a day labor for me.

Net gain for me? About $15,000 grand! Not to gloat but that's not a bad pay day for me!

Now I don't recommend anybody do what I do, but it works for me and it has for a long time.

I Dont normally get into the back and forth with someone who doesnt have all the information he needs but here goes. Using your numbers, you are correct that you will be losing money, however, the average recommended time between tank cleanings is around 4 years. So, using your numbers, you are saving $2500.00. Damage to your drainfield is no doubt occurring as we speak. Damage to the groundwater supplies as well. You see, a septic tank is simply a water/solid separator that allows water to flow outand the solids to stay put. As time goes on, the concentration of sewage increases in the tank becoming more and more harmful to our groundwater. Times have changed and we now look at septic systems in a different light than before. The science behind it is eye opening.

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