Lots of water and the black tank.

John&Joey wrote:
You see to me that is just normal use. Where does this "use a lot of water come in?"

For some reason people get concerned about the amount of water in the black tank and worry about it getting too full - which is practically impossible, unless your black tank is connected to the shower drain.

Today most folks have 1 gallon per flush toilets in their homes, and I would not be surprised if at least half of them flush twice.

Folks can quickly calculate that a 30 gallon tank gets full in 15 to 25 uses if you use a gallon or two for each flush.

What happens is people end up using only a cup or maybe a cup and 1/2 of water per flush.

That simply isn't enough water to wash the solid waste away from the bottom of the tank right under the toilet. It also isn't enough to help liquefy any of the solid waste or TP. It also isn't enough to make any toilet chemicals or enzyme product you have work correctly.

A full bowl of water in the two RV toilets I've had measures just about 2/3 of one gallon of water. I realize some models are more, some are less - but a full bowl of an RV is less water than you use at home to flush.

A black tank 1/2 full or so is 'healthier' than a black tank near empty. It lets the 'system' work.


Dumping

Just like your home toilet - a decent volume of water is necessary to push waste down the drain and out of the system.

Many people want to dump every day or every other day.

Dumping a 1/4 to 1/3 full black tank just doesn't have enough water to move out all the solid matter. Black and grey water tanks are almost always wide flat tanks under the floor - they have a great surface area and little depth to build pressure. Pressure is what pushes the water out faster. With more pressure, the solid waste and TP moves out faster. With very little pressure - it may not move at all.

A full tank dumps faster and cleaner.

Ideally you should only dump a near full black tank. That isn't always possible. But after dumping, you must rinse the black tank. Either with a flushing system, a wand or a grey/black tank equalization. Maybe even just a couple wastebaskets full of water.

You should have some means of seeing the color of the water being pushed out of the black tank, and rinse until the water is clear.

I used my last trailer for 2 years and 2 months - and the black tank sensors worked perfectly the entire time. I expect the keep the sensors in my new trailer working for years.

Corrosion doesn't kill black tank sensors - dried waste does.


Black tanks should also have enough water in them at all times to 'splash' around when you move to wash the inside of the tank and clean it a bit more.


The whole point behind use plenty of water is to ensure the black tank is a temporary storage place for waste. If a person uses just a bare minimum of water - their black tank will be a permanent home to dried waste that never gets washed.

John&Joey wrote:
Also about always leaving the tank with some water in it, what do you think happens to all the non-FT that put there rigs away for the winter. That tank is dry as a bone, the next season there is never a problem.

Always leaving water in the tank refers to the camping season. Not necessarily the winter storage.

During camping season, leaving some water - a couple gallons in the tank helps keep the tank cleaner and healthier.


Now I personally have never seen a black tank that drained completely and did not have some water in the discharge/ valve area. So for winterizing, I always make sure the valve area is protected by RV antifreeze.

The really vulnerable part of the sewer system is the discharge valves and hard, non-expandable plastic. This is often exposed to more extremes of temperature - and might freeze solid at temperatures what won't make really good ice cubes.

Freezing solid is not the problem. A tank/ valve area frozen solid is not inherently damaged.

What causes damage is the expansion of water as it turns to ice. It can put heavy PSI loads onto the most vulnerable parts of the sewer system.

The way we avoid such loads is by putting RV antifreeze into the black and grey tanks in the winter, enough to ensure the waste valve area is saturated with RV antifreeze.

Yes, it will get slushy below about 25 degrees, and it will freeze - however it will not expand until -50F.

But winterizing is another discussion.


The main thing about lots of water is keeping your black tank as clean as possible, with as little solid waste as possible during the camping season.

For people who have black tank problems - the root cause is almost always that they use very little water and keep their tank dry.

We mostly dry camp and as such we are very conservative in water usage. We use minimal water in the toilet. A few ounces for #1, a pint or so for #2. The two of us can go 5-6 days and sometimes 7 days on our 33 gallon fresh water tank before needing to dump waste and refill fresh water. We never add any amount of water to the black tank to start it off. IMO that is an urban legend and a waste of useable tank volume. In 10 years of RVing we have never had an issue with the black tank not draining. When we get home from a trip we give the black tank a good flushing until it drains clear. After that a check down the toilet drop pipe with a flashlight shows no solids below.

As already mentioned - never leave the black tank valve open when at a full hookup site.

Some manufacturers (like mine) plumb the vanity sink to the black tank to cover that (lots of water)issue. DW washes her face alot!

I reckon we need to define "lots" of water. What is lots to me, might not be much at all to you. I usually use 1.46738 quarts per flush #1 and 2.38749 quarts per flush #2. Now we have a comparison in hard numbers. Silliness if you ask me.

You asked and I think several gave a good explanation behind the theory…

I don’t know of any science or test specifically geared for a RV tank, but it is the same theory used by public sewer systems using the science of hydraulics to keep the effluent moving… but in these systems the toilet uses more water and the rest of the household water flows through the same pipe… no so in the RV holding tank…
it’s generally the lack of liquids in any gravity flow systems that keeps the sewer cleaners busy by using pressure and high volumes of water to keep the pipes from plugging up… actually in tight systems cleaning with water becomes a much more frequent issue, in poorer systems infiltrating ground and rain water keeps things moving…
you can agree or disagree, follow the suggestions or not, but using lots of water works well for me… Rv toilets do not normally need lots of water just to empty the bowl…

If we are going to talk about water waste that would be more on the topic of believing the tank needs to be flushed and cleaned after every use, or using things like the sewer solutions water powered pumps are a good option…

You asked the question. You got some answers. You do not believe it. You seem to want to argue the point. You might be right.

Here is what you should do. Drain your tanks. Leave the black tank drain valve open. So all the water continues to drain. Use very little water.

Come back in a month and let us know how that works out for you.

You are a senior member with more than 5700 posts. Been around here for a while. You know the answer.

No more "if it's yellow let it mellow, if it's brown flush it down"

:B

John&Joey wrote:
Also about always leaving the tank with some water in it, what do you think happens to all the non-FT that put there rigs away for the winter. That tank is dry as a bone, the next season there is never a problem.

When I winterize I do a good flush with the Tornado, and then put about a quart of the pink stuff into the tank. It never gets bone dry.

John&Joey wrote:
Maybe, but you know there is much more human fluid then human waste in a 24 hour period. In addition that human fluid is being flushed down with water. Why go out of your way using a lot of water.

X2. It's just me in the RV and I stand in the commode room a lot more than I sit. I also don't have to worry about a DW using half a roll of TP at one sitting.

Lots of people run into problems by dumping the black tank after only a few days use, not enough liquid in the tank to flush all the solids out.

John&Joey wrote:
.. That threads says use a lot of water, but never gives a reason why just using the toilet in a standard way is not enough.

Standard for a household? There's always a good supply of water in that toilet.

Lots of water to me means a good gallon or so with every BM. Water is the main ingredient in breaking down solids, so, when you dump, stuff comes out of there with a vengeance, not a trickle.

That said, you need to go dry camping and test your theory.