how do you keep sewer tank clear

Another no chemicals in the tank. I also use any toilet paper that I have on hand, usually Kirkland brand because that's what I already have in the house.

I always make sure the tank is at least 3/4 full and use a standard 3" slinky not a macerator or water powered sewer solution which drains down a 1 inch hose.

Never had a problem with clogs and the sensors work more often than not.

Where are these RVers getting this Formaldehyde?

“Formaldehyde is a colorless, flammable, strong-smelling chemical widely used to make home building products. Most formaldehyde produced in the United States is for the manufacture of resins, such as urea-formaldehyde, used to make the adhesives for pressed wood products, such as particleboard, furniture, paneling, cabinets, and other products. Formaldehyde is also commonly used as a preservative in medical laboratories, mortuaries, and consumer products, including some hair smoothing and straightening products. It is also a by-product of automobile combustion and is produced in small amounts by most living organisms, including humans.”

Keep them clean? Not to use them.... to keep the debris free as possible, use LOTS and LOTS of water!

Lwiddis wrote:
Where are these RVers getting this Formaldehyde?

Here is one of many places to get a chemical that actually reduces odor.

Thetford 10801

Dump add 10-15 gallons of water. Drive to next stop, dump before leaving, add 10-15 gallons water, continue repeating and the tanks always clean. No chemicals.

Here is my system for lubricating both sides of the blades and the groove of both of my cable operated drain valves including the toilet flush blade/ball valve. Been doing this for 19 years, still have the original drain valves and seals! I do this at the beginning of each season and occasionally in mid season.

First drain and flush both tanks to flush out all solid matter. Close both dump valves.

I have a 3 inch termination cap that has a garden hose bib, attach a small plastic garden hose ball valve to the hose bib to act as a control valve, install the cap on the end of the RV drain pipe with the hose bib/control valve at the bottom position. Shut the control valve. Attach a short piece of drain hose/bucket if desired. I just let it drain onto the gravel next to my RV concrete parking slab.

Put about 5-8 gal of water in each tank (just make sure that you have more than 3 inches in the black tank and more than 1 1/2 inches in the grey tank). Put a pint of mineral oil in each tank. (about $2.50/pt at Wally World pharmacy) When you put it down the toilet with the water turned off, pour a little amount onto the blade (or ball) open and close it slowly, repeat 2-3 times to completely coat and lubricate the flush valve, when you put it down a sink/shower drain that has a "P" trap use a lot of water to flush it out of the "P trap. (Remember that he oil will be floating on the top of the water)

There are 231 cubic inches/ gal of water. If you know the width and length (even the approximate measurements) you can calculate about how many gals to put 1 1/2" and 3" in your tanks.

Open the black tank drain valve about 1/2 way. This will fill the cavity between the drain valve and the termination cap. Open the control valve a small amount, you want a very slow stream of water SMALLER than pencil diameter. Remember that the oil will float on the top of the water. As the water SLOWLY drains out occasionally cycle the drain valve open/close, leave the drain valve about 1/2 open until the next time to cycle it. As the oil/water interface lowers this will ensure that both sides of the blade and the groove is coated with oil. I have always been been able to feel the ease of blade movement when the oil is coating the blade.
Repeat doing the gray tank drain valve.

To lubricate the cable I just pull out the handle opening the valve, apply a few drops of light weight oil to the exposed shaft, operate the valve a few times, repeat a couple of times every year, after a few cycles capillary action will siphon the oil full length of the cable.

Lwiddis wrote:
Where are these RVers getting this Formaldehyde?

“Formaldehyde is a colorless, flammable, strong-smelling chemical widely used to make home building products. Most formaldehyde produced in the United States is for the manufacture of resins, such as urea-formaldehyde, used to make the adhesives for pressed wood products, such as particleboard, furniture, paneling, cabinets, and other products. Formaldehyde is also commonly used as a preservative in medical laboratories, mortuaries, and consumer products, including some hair smoothing and straightening products. It is also a by-product of automobile combustion and is produced in small amounts by most living organisms, including humans.”

I suspect that people are working off out-of-date knowledge. Wasn't that long ago that all black tank chemical treatments were formaldehyde based. People don't read the contents of what they buy, just assuming that it is what is always been.

Gary Haupt

ScottG wrote:
We camp mostly over weekends and dump as we leave the CG. So checmicals don't have enough time to break down anything.
However, I still use chems. Why? Because I don't want to be "that guy" that stinks up a city block while he's dumping. The few cents it costs is insignificant.

They make almost no difference.

What DOES make a difference?
Well twice I've been that guy you don't want to be
Both times I left a valve open and the "Stink" was coming out of the hole in the ground. Closed the valve and stink gone.

garyhaupt wrote:


I suspect that people are working off out-of-date knowledge. Wasn't that long ago that all black tank chemical treatments were formaldehyde based. People don't read the contents of what they buy, just assuming that it is what is always been.

Gary Haupt

Thetford 10801 still contains formaldehyde, that is why I linked in my previous post. And since it does contain formaldehyde, it does a good job of keeping the stink under control.

rav wrote:
never use chemicals. I drain the tank, use the built in flush, close valve and let fill up for about 8 to minutes (yes I use a timer) then dump, flush and then add about 5 gallons to the tank. We do have a water softener so that helps keep the tank "slick", sometimes I will put some laundry detergent in the tank.

Ditto. Sometimes use a little Dawn dishwashing liquid. Squirt before we head home and dump at our storage area. Very convenient. Slippery right out the tube. Zero stinky. We too use the restrooms for solids when possible so none or very little solids.

We use the anti-stink tabs. For us they worked great. Forgot one time and we could tell, not bad but wafty.

Early on, the 1/3 was always on even when the tank was empty. Filled with 5 gal of hot water, a drop or two of soap and drove 5 miles. No problem since.

To each their own. This is what works for us.