Holding tanks

[merlin]

We are currently cruising around the Med in our british registered yacht and want to fit a holding tank for use in anchorages. We are currently in Spain and hope to cruise through Italy and Greece to Turkey. Does anyone know of any regulations for holding tanks, or any guidelines for sizing? We don´t want to fit a convenient size tank and then find that when we arrive in a country we have to supplement it or refit a larger one.

Thanks,

Merlin.

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[MedMan]

There are no regs as to size - that would be up to the Flag State and the UK has no such regs for pleasure yachts. The law in Turkey just says you cannot pump out anything in harbour so it's up to you how many days worth of waste you want to be able to hold. If your tank will only hold enough for 24h and you want to stay a week you will be up at 0300 looking very furtive and hoping you don't have to break into the piggy bank next morning to pay a £1,000 fine. At the end of the day it comes down to how much room can you spare. Make it as big as you can without sacrificing space for fresh water and fuel.

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[Talbot]

I was provided with the following data by "Headmistress" who is the resident guru on marine sanitation. Even the data on Tek Tanks site is derived from her bible on the subject:

<font color=blue>What Size Holding Tank Do I Need?

There really aren’t any hard and fast answers to this question. There have been numerous and sometimes arcane attempts to arrive at one, but what it really comes down to 99% of the time is: how much space there is in the boat to put one--or (more often than not) more than one if the boat has two or more heads. The hose run from either head to the tank shouldn't be longer than 6-8'...10’ is the absolutely maximum. Any longer, and you'll always have waste sitting in the hose to permeate it. So, if the location you’ve picked means it has to be longer, find another location for the tank that's closer to the head. If you have two or more heads, you may need two tanks...or--unless you're in "no discharge" waters--a Type I or II MSD on the head you use the most and a tank on the other one.

Here's MY rule of thumb--and it's based on the size of the boat:

under 30': 12-20 gallons.

30-35': 20-30 gallons.

35-40': at least 30 gallons...

40' plus: at least 40 gallons total, more if you have room.

There are just too many variables to do it any other way, different types of toilets use different amounts of flush water and people are different, but the following information may help you decide. Just remember that no one has EVER complained that his holding tank was too big!

Vacuum toilets and electric macerating toilets that draw off the onboard pressurized freshwater system use the least flush water--1-3 quarts/flush.

Manual toilets use about a gallon/flush if pumped long enough to completely rinse the sewage out of the head discharge line. There are ways to cut down on that--rinse out the line once a day instead of pumping enough water through with every single flush, but the average will still be at least half a gallon, whether the toilet has a piston/cylinder pump or a diaphragm pump.

Electric macerating toilets that have integral raw water intake pumps need 1-3 gallons per flush, because there's no way to switch to "dry bowl" without frying the impeller in the intake pump. A couple of brands/models have separate pumps using separate motors, which cuts the water consumption considerably, but you still have to run enough water through it to clear everything out of the macerator and pump unless you want to deal with clogs.

The further the tank is from the head, the longer ANY toilet has to be flushed to move the bowl contents from the head to the tank.

Those are the parameters for the toilets. Now we need to factor in people: Women go to the bathroom more often than men (women also tend to use about 5x the toilet paper that men do, but that's another issue). Children tend to fall somewhere in between women and men. The average urine "deposit" from an adult is about a cupful (6-8 oz)...somewhat less for children, depending on their ages because their bladders are like the rest of their bodies--they grow as the child grows. Some people drink more liquids than others...some sweat more of it out than they process through their kidneys...and that can vary with the time of year.

Keep track of how many times you have to use the toilet each day...multiply that by the average volume...then by the amount of flush water your toilet needs, add at least one flush/person/day for solids too (double the flush water volume for that) and you'll come out with the same answer I always do: it's totally impossible to find enough space--at least space you're willing to sacrifice for tankage--for a tank on your boat that will last 4 people a week without a pumpout--and it's unlikely that even two people won't fill it in 4-5 days--unless the lee rail gets a LOT more use than the toilet.

So we're back to my "rule of thumb"...or smaller if there isn't even that much room.
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[snowleopard]

out 50 gal tanks last us 3-4 days with 2 on board.

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[Anonymous]

>>out 50 gal tanks last us 3-4 days with 2 on board.<<

Presumably you divert all toilet waste (solid and urine) to the holding tank during those times? Do you find that you can sometimes justify discharging urine direct out to the sea, holding only the solids? After all, from healthy people, urine is almost sterile and certainly shouldn't contain any pathogens. The ancient Romans used it for washing clothes, so I believe,

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[Gunfleet]

The ancient Romans? I think you will find King George's Navy used it in that way too!

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[roly_voya]

Yes but king goerges navy stank to high heven!

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[Metabarca]

There are no regs about holding tanks in Italy or Croatia (except for charter vessels).

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[boatless]

I've no doubt that Peggy (The Headmistress) will turn up soon to confirm this, but the grey waste (soap containing from washing, showering) is far more harmful than any of the stuff that we humans produce. Those of us with a normal diet anyway.

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[Gunfleet]

Just how old are you?

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[Anonymous]

>>but the grey waste (soap containing from washing, showering) is far more harmful than any of the stuff that we humans produce.<<

I read recently, probably in the New Scientist, that raw sewage per se is nowhere near as dangerous as we are led to believe in the West and that it is the creatures that live on the sewage that spread much of the disease we associate with sewage. This is not an issue for sewage discharged direct into the sea. However, we've all swum in the sea and come across a floating turd, pieces of paper or small faecal particles and it is utterly revolting and totally unacceptable. I am not trying to justify dumping raw sewage solids into anchorages or off beaches when bathers might be expected, but why not urine where there is an appropriate current, particularly if people discharge it without much, if any, paper.

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[merlin]

Thanks to everyone for their useful information (and history lessons). Further research (of the semi-anecdotal type i.e. from those who should know, but undocumented), reveals that allegedley the CE requirement is 8 litres for each CE 'registered' berth (CE categories for newish boats). Also allegedly the Spanish version for Spanish flagged boats is 4 litres per person per day with a minimum of 2 days - about the same as the edict from EU Lords and Masters. From the replies though it seems that nobody really checks so as long as we are happy wth the facility and our ability to avoid pollution versus tie knots in anatomy, we´ll install the one that fits best.

Thanks again,

Merlin.

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