ADDING A BLACK TANK

tonyidle

tonyidle

Joined
Aug 6, 2013
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Kendal, Cumbria
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27,352
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Le-Voyageur RX958 Pl
Exp
since 1999
I'm planning to convert my toilet to one that uses a black tank. Installation will be made easier by the fact that the holding tank will be directly below the toilet. My question, to those who already have the system, is how big are your tanks and how long before you need to empty. We normally empty the cassette twice in three days so I can extrapolate from that however your experience might be more informative. Thanks.
 
How big is the factor , also its not just the tank as you need room for plumbing quite large bore , inc a link to grey tank for flushing thru hose , plus hose storage .
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It is also a good idea to carry a macerator https://mobilervmaintenance.co.uk/product/flojet-macerator-waste-pump
as its also not always possible to dump at ground level , so you need a macerator dump hose as well .https://mobilervmaintenance.co.uk/product/flojet-macerator-waste-pump
pump-1.png

My US RV had a 225 litre black tank , 2weeks usually easy .
 
I'm interested in adding a black water tank, though would how does it effect where you can dispose of the contents etc . Would it need to be chemically dosed? Also is it normal / possible to use the original Thetford toilet basin , if so how is it linked to the BW tank ?
 
Interesting, but the installation plus the weight of stored black waste would wipe out a lot of payload, making it non feasible on most European vans
 
We have a black tank on our Hymer , bit of a rarity, but adopts a different take to the RV

our toilet looks more conventional although still plastic, fitted with a macerator pump on the outlet so it delivers poo soup to the black tank that can be discharged by gravity alone

We dump black first then the grey through the discharge pipe (If used) to flush it through

we need a hose most times, including home where we are lucky enough to have a manhole close to where park the MH

We also chose to carry a standard cassette which we can fill by gravity if no low level dump option available, been used three times in 6 years

we only have a small black tank, 45 litres from memory , but can easily do a 3 night weekend away and return home to empty if no dump option as is common on rallies

I would not chose to have another if we change MH’s

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TheBig1 said:
Interesting, but the installation plus the weight of stored black waste would wipe out a lot of payload, making it non feasible on most European vans
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I take your point but a weeks 'worth' would likely be no more than 60 litres and its offset by the fact that you can use the grey water as a source..so true additional weight would maybe be in the order of 20kg...! not a bad price for a whole week or more of sanitary peace!
 
My Thetford tank was about50l & I use to empty whenever I could as rarely used sites. It had the 3" outlet so was easy for ground dump emtying with a slide valve. If no ground dump then I could always use a bucket as the van skirts where high enough from the ground to get one under. The only type of emptying not possibel was if it was in to 1 4"/100mmm soil pipe at a higher level.
 
DavidG58 said:
We have a black tank on our Hymer , bit of a rarity, but adopts a different take to the RV

our toilet looks more conventional although still plastic, fitted with a macerator pump on the outlet so it delivers poo soup to the black tank that can be discharged by gravity alone

We dump black first then the grey through the discharge pipe (If used) to flush it through

we need a hose most times, including home where we are lucky enough to have a manhole close to where park the MH

We also chose to carry a standard cassette which we can fill by gravity if no low level dump option available, been used three times in 6 years

we only have a small black tank, 45 litres from memory , but can easily do a 3 night weekend away and return home to empty if no dump option as is common on rallies

I would not chose to have another if we change MH’s
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Interesting last line...can you expand on the reasons as to why you wouldn't have another?
 
DavidG58 said:
I could achieve virtually the same capacity by carrying an extra cassette , much more convenient to use at a lot of sites 👍
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yes to be fair that is the way my thoughts where originally inclined. 2 cassettes would give about 4-6 days endurance which is similar to or more than that of our fresh water and so would require a replenishment anyway!

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ianp said:
yes to be fair that is the way my thoughts where originally inclined. 2 cassettes would give about 4-6 days endurance which is similar to or more than that of our fresh water and so would require a replenishment anyway!
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And you save yourself a load of work if you try to add one

Plus possible future aggro , our macerator packed up which then meant we couldn’t use the loo till fixed 🤔
 
I’ve been thinking the same for a while, and decided this week with the underlings (20 and 17) with us that I don’t like dumping on a daily basis, especially as we prefer to to wild camp. Finding dumping sites is a pain.

I’m been pondering for a long while. I’m planning a 60l tank, with a 12v macerator pump on the outlet with a 1 to 1.5 inch hose. The pump I’m looking at says it can pump 60l/min max, and upto 3m in height. Which should be fine, if true. It also has a hozelock rinse port. I’m also planning to link to the grey discharge to allow rinsing of the hose.

I’d like the option to still use a cassette too - eg if the pump fails when we are away.

I’m thinking of cutting a hole through the base of the cassette holder and the floor to provide access to the black tank. I will then install a removable tight-fitting pipe (presumably with sealing rubber flanges) to connect the toilet to the tank. Tank will need to be vented to the roof also I guess.

If I want to revert to cassette I will remove the pipe and (somehow) seal top of the tank, before inserting my cassette in the usual way.

Any thoughts? Anyone have advice or see obvious flaws in this setup?
 
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ianp said:
I take your point but a weeks 'worth' would likely be no more than 60 litres and its offset by the fact that you can use the grey water as a source..so true additional weight would maybe be in the order of 20kg...! not a bad price for a whole week or more of sanitary peace!
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Hi ianp, can you explain what to mean by the bold above? Thanks.
 
I wouldn't have though it worth while unless you can at least a 100 Lt tank.
We carry spare cassette and can last at least 6 days with 2 of us with everything going in it, it's a swivel bowl. Last van had a bench one with a spare could last 8 days.

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Our new to us van has a 90ltr black tank but it is not something I will be bothering with. We have a Thetford ceramic loo with a cassette, when the cassette is full the panel has a light that lets you know then press to pump into the main tank and start to fill your cassette again,

It’s just as easy to empty the cassette every day or two, it would not have been an option I would have ordered had I bought the van new.
 
Lenny HB said:
I wouldn't have though it worth while unless you can at least a 100 Lt tank.
We carry spare cassette and can last at least 6 days with 2 of us with everything going in it, it's a swivel bowl. Last van had a bench one with a spare could last 8 days.
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You may be right. 60l would give us 6-ish days when just two of us. I figured this would probably be enough. But there is space for a bigger tank - it’s then a trade off with weight.

Also a second cassette means storage space used.

I’m looking for a solution as “hands off” as American/Canadian RVs I’ve hired, but tailored to UK/European facilities - hence a macerator and pumped narrow-bore pipe seems to cover all eventualities.
 
Steve and Denise said:
Our new to us van has a 90ltr black tank but it is not something I will be bothering with. We have a Thetford ceramic loo with a cassette, when the cassette is full the panel has a light that lets you know then press to pump into the main tank and start to fill your cassette again,

It’s just as easy to empty the cassette every day or two, it would not have been an option I would have ordered had I bought the van new.
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TBH, in Europe and UK, a black tank is a PITA. Almost nowhere has suitable dumping facilities, even with a macerator and a length of flat hose. Unless you exclusively plan to dump at home, I'd stick with a cassette.
 
cmcardle75 said:
TBH, in Europe and UK, a black tank is a PITA. Almost nowhere has suitable dumping facilities, even with a macerator and a length of flat hose. Unless you exclusively plan to dump at home, I'd stick with a cassette.
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And we had a 110 litre black tank. Would have swapped for a 21 litre cassette in a heartbeat.
 
cmcardle75 said:
TBH, in Europe and UK, a black tank is a PITA. Almost nowhere has suitable dumping facilities, even with a macerator and a length of flat hose. Unless you exclusively plan to dump at home, I'd stick with a cassette.
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I was assuming with a pumped hose, I could use pretty much any cassette emptying facility I’m likely to come across?

Or is that a wrong assumption?

Anyway, to be able to dump only every week or two would be ideal, and mean mostly we can cope til home.

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Glas Robin said:
I was assuming with a pumped hose, I could use pretty much any cassette emptying facility I’m likely to come across?

Or is that a wrong assumption?

Anyway, to be able to dump only every week or two would be ideal, and mean mostly we can cope til home.
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The problem comes with parking close enough to the dump station. Frequently, the black dump station does not have parking for a motorhome within reach of your hose. Typically in Europe, the black waste dump point is located as part of the shower block, which is often not near the access roads, and even more rarely somewhere you can stop without blocking the road. Sometimes it can be reached, or there is a dedicated MHS point, but it is hard to know in advance, as it isn't something campsites generally advertise. If you typically do 5 day trips, you can just bring it all home with you.
 
I have a 47 us gallon black tank and two us 47 gallon grey tanks , it was asked how long before empties at a push ten days with the two of us.
We use a tote tank and find a sewer manhole ,usually near the toilets on a site if our hoses cant reach.
It does limit things in one way but in my opinion better than carrying a poo box around every other day.
Everything is a compromise and what works for one dont work for another .There is no right or wrong only what works for you (y)
 
tonyidle said:
I'm planning to convert my toilet to one that uses a black tank. Installation will be made easier by the fact that the holding tank will be directly below the toilet. My question, to those who already have the system, is how big are your tanks and how long before you need to empty. We normally empty the cassette twice in three days so I can extrapolate from that however your experience might be more informative. Thanks.
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65 US Gallons, and we can easily go a couple of weeks before we need to ’dump’

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If we can’t dump easily, we have a 15 gallon wheeled tank, that I can tow using my bike, so can empty like a cassette should I need to, so perso can’t see any disadvantages
 
Larger Black water tanks are common on boats, thus the marine industry maybe the area that you can look too for help & guidance.
I fitted a 200 litre poo tank on our Pedro 33 boat. I used a company called Tek-tanks for the tank & fittings. They have a large selection of standard & custom made tanks & all the fittings you will ever need.
If you go online try the following for a start : Tek-Tanks, Jabsco, Force4 , Leesan. There are many more.
There are many options, the standard Jabsco marine toilet used a 32 mm dia hose, without the need for a macerator. There are vacuum systems available. Thus the loo can be remote from the tank.
There is a lot to consider. You must use the correct odor proof materials for the tank, pipes & fittings, otherwise your van will smell.
The tank will need an empty point. A vent pipe, ideally with a carbon filter. A flush water point, Marine tanks are normally emptied using a vacuum pump system which is not suitable for motor homes. But you could use a gravity emptying pipe or a vacuum hand pump or both.
You will need a access hatch & some form of level gauge & indicator.
All the above are normal on a marine waste tank & there are many manufactures who have standard units or can make a tank to your dimensions. If you are mechanically minded this could be a great project.
Clearly there are good reasons why large black water tanks are not normally used in motor homes. Mainly the weight & space requirement.

I used to design sewage pumping stations in my drawing office days & spent many a happy hour paddling around in my wellies up to my ankles in Poo. We all love a good toilet thread SO GO FOR IT.
 
Laila EcoVip motorhomes always had a black tank system. They could tow three tonnes as well, but I digress🤭
 
If you want to go black tank for a self build MH in the UK (knowing the advantages and disadvantages), I'd buy USA RV style fittings. They're usually pretty cheap and spares availability is good, once you get your head round everything being in inches. Make sure you have a macerating pump for emptying. Anything marine seems to attract a massive premium, just like anything to do with horses.

You should also consider just buying a few extra cassettes and finding somewhere to store them (full), if you just want to extend off grid excursions beyond a couple of days.

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