Care and Feeding of Toilet Holding Tank??

As a newcomer to RVing, one of the difficult questions about which to ask and to get reliable information is how to properly use, maintain and flush holding tanks. 

Can the valves be left open while parked?

At what level should the tanks be emptied?

How is the best and most hygienic way to dump holding tanks?

Should chemicals be used?

If you have comments about the issue, or would like to talk about holding tank maintenance, post your question here. 

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Though the valves can be left open when parked... It's best to let the tank fill at least 1/3 and then "Dump" (you can leave the hoses connected while parked)

Dump & flush the black, then dump the gray tank (This flushes out the black from the hose)

If you choose to use chemicals in your tank to controle order... Look at what chemicals are in the package.. If it says "FORMALHIDE" put it back on the shelf and look at something else

Tissue: Scott's, forget the stuff at the RV store, Scott's

One of the manufacturers of tank flush accessories recommends allowing the contents of the grey water water tank to flow into the black tank to allow the soapy water to wash the black tank.

Is this a procedure that would be recommended by seasoned RVers?

Steve said:

One of the manufacturers of tank flush accessories recommends allowing the contents of the grey water water tank to flow into the black tank to allow the soapy water to wash the black tank.

Is this a procedure that would be recommended by seasoned RVers?

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Nope!! Keep them separate. I would be afraid of black water residue backflow into the grey water tank.

Regards,
Liz
Fulltiming for 11 years.

Can the valves be left open while parked?

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Grey tank, yes.? Black tank, no.

At what level should the tanks be emptied?

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Black tank 2/3 full.? If short of that, fill to 2/3s with a hose.  Grey tank, anytime.

How is the best and most hygienic way to dump holding tanks?

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Just before dumping, close the grey water tank and allow it to fill to about 1/3.? ? At that point, if the black tank is 2/3 full, open the black tank's valve and dump.? ?When the black tank is empty, close the valve.? ?Now open the grey tank's valve and let it dump.? That will act to clean the sewage out of the sewer house -- grey water will be soapy but you can urge it along by adding a few squeezes of soap before dumping to aid the cleaning action.? ?Close the grey valve if you are going to move on.? Uncouple the sewer hose at the tank end, keeping it elevated wash it out with water from a hose.? ?Now uncouple it from the sewer coupling, remove the terminal plumbing wash, and stow all away.? ?You should wear heavy rubber gloves for this whole procedure -- I like the ones sold in hardware stores for chemical workers.? ?Keep a gallon of ordinary bleach and a small, 2-gallon bucket handy for cleaning up accidents.

Should chemicals be used?

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Not really.? Your black tank is a septic tank, and septic tanks work by biological action:? gazzillons of liddle bacteria chewing away.? ?Chemistry generally acts to kill bacteria -- that is why most contain formaldehyde.? ?You may want to encourage the little rascals by adding some septic tank bacteria, stuff sold in septic tank country, but I never have.? ?Grey tank stink can be cured with a bit of bleach, or simply dumping.

And as John said about tissue -- fergit the RV store TP, use Scotts or another paper approved for septic tank use.    See also the latest exclusive RVForum TP tests.



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Your black tank is a septic tank, and septic tanks work by biological action

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My understanding of a septic tank is a multi chamber facility where the bacterial action degrades solid matter and separates the water and allows it to flow into the ground.? Wouldn't our black tank just be a holding tank because it is unlikely the contents would remain long enough to break down.? Most of us dump our tanks every few days.

I understand holding tank chemicals are formaldehyde free and their function is to release solid matter from sensors and to lubricate the dump valve.

Many of the Framily have learned that it is not necessary to add chemicals to your holding tank. If you feel you must use something use a enzyme product such as Pure Power or even Ridex but NEVER NEVER NEVER use any product that contains formaldehyde or anything that ends in hyde. Formaldehyde is an excellent preservative.  Why would anybody want to add a preservative to their black water tank and preserve the contents their black water tank??? 
For anybody that has been preserving the contents of their black water tank I would suggest throw that product away, or give it to your worst enemy, and add a 1/4 cup of Dawn to your BWT then drain and rinse several times.  One application of Dawn should do the trick but It will take some time to recover from the damage done by the hyde products.  In this case bacteria and enzymes are your friends don't kill them off.

Jackliz said:

I would be afraid of black water residue backflow into the grey water tank.

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You need to use a check valve that allows flow in only one direction to prevent the black stuff getting into the grey tank..

You need to use a check valve that allows flow in only one direction to prevent.

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A check valve would, of course be required in the fresh water line being used to flush the holding tanks, but I was referring to and I suspect Liz was also alluding to some proponents of leaving the black water dump valve open while the grey water tank is being dumped.  The rationale is that the grey water will wash the black tank as it backflows into the grey tank.

My opinion is this practice allows for contamination of the grey tank, which may not be sealed off if the P traps in the sinks and shower become dry resulting in black tank smell coming into the coach.  Does anyone share my opinion or is this practice of grey water backflushing acceptable?

Steve said:

My opinion is this practice allows for contamination of the grey tank, which may not be sealed off if the P traps in the sinks and shower become dry resulting in black tank smell coming into the coach.? Does anyone share my opinion or is this practice of grey water backflushing acceptable?

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I would not do it.  Just don't think its a good idea.

I put a cup of Arm and Hammer Washing Soda in my BWT right after I drain it. So far this has kept it clean and relatively sweet smelling.

Woody

I put a cup of Arm and Hammer Washing Soda in my BWT right after I drain it.

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Do you dilute it in the toilet bowl before dumping it into the tank?

Steve said:

... I was referring to and I suspect Liz was also alluding to some proponents of leaving the black water dump valve open while the grey water tank is being dumped.

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So was I Steve, although partly in jest. The black pumps on the boat each have 4 duckbill vlaves, which are essentially check valves. However, their marine purpose is, for example, to prevent sea water coming back into the black tank. Their diameter is too small for our black water systems on RVs, but something similar (of the right size) attached to the grey water outlet would do exactly what I suggested, albeit in jest.

Steve said:

My understanding of a septic tank is a multi chamber facility where the bacterial action degrades solid matter and separates the water and allows it to flow into the ground.? Wouldn't our black tank just be a holding tank because it is unlikely the contents would remain long enough to break down.? Most of us dump our tanks every few days.

I understand holding tank chemicals are formaldehyde free and their function is to release solid matter from sensors and to lubricate the dump valve.

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Your black tank is a single chamber septic tank.? ? Wikipedia says about septic tanks:?

An Imhoff tank is a two stage septic system where the sludge is digested in a separate tank. This avoids mixing digested sludge with incoming sewage. Also some septic tank designs have a second stage where the effluent from the anaerobic first stage is aerated, before it drains into the seepage field.  Waste that is not decomposed by the anaerobic digestion eventually has to be removed from the septic tank or else the septic tank fills up and wastewater discharges directly to the drainage field.

In-ground septic tanks have to be pumped every few months.  You do not have worry about sludge in an RV tank since you will dump the whole mess in 3-5 days.  Therefore, only one chamber is needed.  The septic action serves to break up solids and paper tho so it is worth encouraging.

A lot of RV chemicals do contain formaldehyde/formalin or formalin generators.  If any of the listed ingredients have the syllable form-, that's the stuff.

Does anyone share my opinion or is this practice of grey water backflushing acceptable?

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I share your opinion in spades.  If you must backflush a blacktank use a backflushing elbow and flush with fresh water from a hose bib protected by a vacuum breaker/anti-siphon valve.