black/grey ratio to freshwater

[bagmaker]

From your experience -what would y'all recommend as sizing of black and greywater tanks compared to the capacity of the freshwater tank?
All the searches (blackwater size only) I have done come up with a capacity which differs wildly due to the user's different needs, many are happy with a cassette, some need more. A considered figure is about 10 litres per day per person for blackwater capacity. I am not sure if that is accurate, a flush is about 5 litres of "product" (?).

So I figure a better idea would be to size it to the flush capacity you have in the fresh tank.
Do most fill with fresh and dump at the same time or do they fill 3 times as much as dump or perhaps vice-versa? This would have average out somehow for an accurate theory I guess.

For example, I have 1000 litres of freshwater onboard for 2 people. At 50 litres per day per person total usage the tank should last 10 days.
In 10 days those 2 people might have produced 200 litres of well macerated stuff so the ratio would be about 5:1 freshwater tank volume to blackwater tank volume.

That gives a ratio regardless of capacities or time or number of people. Your thoughts?

Expanding on that, the grey water tank should hold around 650 litres leaving another 150 litres of our original 1000 to evaporate somewhere.
So the freshwater volume to greywater volume should equate to around 3:2 as a ratio

Thanks for you insights into a murky area

[dapope]

We have a 320l capacity fror fresh, 200 grey and 80 black. Gives us about 5 days with careful use, they grey being the one to quit first. Black will last up to 10.

[Busman]

We have 500 fresh, 250 drinking (can top fresh with some in needed) 250 grey and 250 black
Usually dump fill whenever available.
What we find as Martin has is that grey quits first, once the water don't drain from the shower we transfer some of it into the black that always has room and then get out the books to look for the next dump point.
Toilet is typical domestic one from Bunnings, all the comforts of home so probably uses bit more flush than a typical RV one.
William

[T1 Terry]

Something that came up on the Caravaner forum is worth mentioning here, the water from the kitchen sink is considered black water by the majority of authorities on the subject. With this replumbed so only the shower water was stored as grey water, it could then be a source of flushing water for the toilet, now the ratios would change considerably I would think.
Of course, those that choose to use the cassette system would not have the opportunity to replumb the kitchen sink, so the reuse of shower water would be limited unless separate grey water tanks were used. In the case of the black tank users, a second black tank for the combined kitchen sink and toilet could extend the period before a dump point was required.

T1 Terry

[BruceS]

Pretty strict regulations for craft on the River Murray and ONLY toilet goes to blackwater & everything else goes into grey water.
Every boat has to be checked and certified.... displaying compliant sticker in prominent position.
If all black & grey water needs to be held & emptied in dump points I can't really see why one tank for everything wouldn't be a better option.
I think a lot (most?) grey tanks have a vent/overflow in case of full tank whereas black don't.
I advise everyone to have the grey water tank overflow .......... much better than flooding the shower water back in to the MH!!! (when emptying the sink)

[bagmaker]

only 2 takers for quantities so far, thanks guys, average seems it should be about 20% blackwater capacity compared to fresh.

How did your shakedown trip go William??
Having just purchased a MH that I need to relocate from Rockhampton to southern vic, I am a little nervous.......

[BernieQ2]

I don't think that Carol and myself could possibly fill a 44 gallon drum with shite in 10 days, we can almost go 5 days with the cassette.
Depends on my beer intake as pee is the bulk in any black/cassette tank.
Bernie.

[Dot]

Sorry I am not good at ratios so this is our We have the vac loo and uses very little water (500ml pr flush). We have 2x15lt cassettes. Easy enough to dig a hole if needed or hang ten till dump point, one usually lasts 4 days (depending on diet) I don't pee in the loo every time I like the lemon tree hunt I figure if all the animals can water the ground then so can I (as I am also an animal) Grey tank is 176lits,(empty as often as we can) Fresh is 376 lits. We wash up mostly in a bowl )after scraping 99% of stuff off the plates etc) and try to water trees with the water. Our tank sizes were born from the available space we had.

[brett&kat]

Hadn't thought of getting a second cassette for the toilet. Don't have a grey water tank yet, but the two lean mean pissing machines that Katherine and I have got can fill a cassette in no time

[dapope]

Hadn't thought of getting a second cassette for the toilet. Don't have a grey water tank yet, but the two lean mean pissing machines that Katherine and I have got can fill a cassette in no time

Less beer.