Fitting holding tanks

Becky

Becky

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Now I have the inverter sorted, one of the winter jobs will be to fit holding tanks. So now a question about these things.

The marine Discount Store in Fareham, Percy Seas or some nsuch name, has some 'ordinary' tanks for water and possibly fuel, and suggested I could use one for a holding tank. Obviously it is hugely cheaper than a designated holding tank, which if I undertsand the Headmistress correctly is made of tougher plastic that doesn't easily let the smell seep through.

Then there is size. Jabsco sell a 5-gallon kit with all the taps and things. But I think that 5 gallons is too little. I could fit a bigger tank, high up in the aft loo, but in the forward loo it would be below sea level, so would need a pump to empty.

Anyone done this? If so what problems did you encounter? Is there an easy or cheaper way of doing the job?

I know I am letting myself get ribbed about this, but women do use a bit more paper and water than the guys do, but then generally we are cleaner. But this means that when a woman is on board, the toilet capacities need to be larger. Anyone give SENSIBLE comments on holding tank capacities?

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The following is from the "Headmistress" and is from her book:

<span style="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.
</span>
 
Thank you, Mark. I have read the book; it was leant to me by a Forumite. It is certainly the definitve instruction book on the subject.

Trouble is you are in SUCH a pickle if the installation isn't right. Or blocks up.

Not something I am looking forward to doing. But on the other hand, it will surely become mandatory soon anyway.
 
As large as possible...

There isn't a definitive answer, but you'd be best to get tanks as large as you can sensibly fit in. I have a stainless-steel holding tank of around 50-60 litres, fitted in a locker behind the toilet and emptied by gravity. It seems OK for a couple for 2 or 3 days. The gravity emptying is a very easy solution, with minimal extra plumbing needed, but I'd prefer to also have a deck pumpout facility.

Before you decide, take a look at the Lee Sanitation website, where there's a lot of useful reference material, diagrams and prices.
 
Almost certainly will become mandatory before any facilities are available for pump out!

You might consider the saddle tanks that go round the base of the loo.

If deciding on a proper holding tank, I recommend a look at Tek Tanks, who have all the stuff and knowledge.
 
I fitted one in my last boat. As space was very tight I made a cardboard mock-up which I took to tek-tanks. They made a perfect copy.

Admittedly the tank did not quite fit (my fault) and needed "adjusting" which tek-tanks did whilst I waited.

Incidentally, never used the dammn thing in action anyhow!

Would not compromise on materials or installation unless you want your own personal "melt-down"
 
I was fortunately enough to have a tank that was fitted by the previous owner. It is 40l and custom made for that boat to fit in a special space. All I had to do was to add conversion to empty it at the dock, a trivial task in this case (it became mandatory here by 2005). We find the capacity enough for three people since we only use it underway.
 
Anyone got a link to the saddle tanks mantioned above? SWMBO doesn't like the chemiloo, and nor do I as I'm the poor sod who deals with it. Saddle tank if large enough with deck fitting may be less nasty. Getting a pull Thetford tank up our steep companionway is fraught with peril to foul to contemplate.
 
Holding tanks

are a subject about which yotties appear to have a neurotic fixation.

During 5 years in the Med I've nor yet found an operating pump-out system, despite the 1972 protocol. (There was one at Bonifacio, which never worked for the 4 years I visited and had been tidied away by my last visit).

There are a few countries where stringent reacreational-boat waste regulations are in force, UK Inland Waterways, Intracoastal and Florida Everglades are ones that spring to mind.

In fact the greatest environmental damage is done by the anionic surfectants, which means that grey water tanks need to be fitted.

As Peggy points out it's almost impossible to find sufficient room in your average boat to store all the pump-out for a crew for more than a few hours.

If one does need to pander to ones' anal obsession, caused no doubt by excessively strict potty training, fit a recirculating toilet like a Portapotti.

No point in agonising over, or wasting money on, something ineffectual.

Oh! I've got a 25 l buffer tank (the more correct terminology) which does an overnight stop for 4, to be pumped out at sea.
 
Re: Holding tanks

Tank materials - I think stainless is a dreadful material. A friend of mine had one which perforated after 4 years from new.
The chemistry is pretty obvious. stainless is only corrosion proof because of an oxidising environment. Sewage absorbs oxygen, gives a reducing environment. In addition chloride ions in sea water plus sulphide (bad egg gas pong) leads to hideous crevice corrosion. Use plastic. As already said Tek tanksseem to know what they are talking about and will make tanks to any shape if you send them a mock up.
The piping is so large its a nightmare so good luck.
 
Re: Holding tanks

Since writing my book, I've discovered that there's another--perhaps better--way to calculate holding tank size...and besides, the "rule of thumb" in my book directed to boat owners in the US where holding or treatment is required in ALL waters...direct discharge from the toilet is only legal in open ocean at least 3 miles from the nearest point on the whole US coastline. So more tank capacity is needed on boats in the US than is likely to be needed on boats in the UK or European coastal waters.

Consider the following when calculating the "right" size holding tank for you:

The difference in cost between a 5 gal tank and a 10 gal tank (btw, our gallons are 4 quarts, yours are 4 liters...hence the difference between a US gal and an Imperial gallon)) is only about 15%...plumbing and accesories cost the same. So IMO, anything less than 10 gallons doesn't hold enough to be worth the effort and expense to install it.

The average flush from most marine toilets is about 2 liters. The average adult averages 5 trips to the head in each 24 hours. So each person continuously aboard *in waters where waste must be held* will put 10 liters/day into a tank...2 people will put 20 liters/day into a tank.

So the "right" size tank for your boat depends upon a) where you'll be spending time continuously aboard--mostly at sea or in other waters where you can flush directly overboard, or in a "no discharge" harbor....b) number of people typically aboard and for how long...and c) availability of pumpout facilities and/or easy immediate access to waters where you can dump the tank.

Do you only need a tank to last 2 people for an overnight in a harbor or anchorage? Or do you spend days on the hook?

Keep in mind too, that even in an anchorage, unless there are a zillion people aboard, all "recycling" a LOT of beer, there's no ecological Or aesthetic reason to send urine only to a tank...so why do it? Save your tank capacity for solid waste and flush water.

When you've taken all that into account and done the math you should be able to arrive at the capacity you need now and for the foreseeable future.

I'm not a big fan of saddle tanks...they only hold 5 gals, not enough to be worth the expense, and the make sitting on the throne very uncomfortable. If you don't have space for tank with a marine loo, consider replacing the toilet with one of the 5-6 gal portapotty models designed to be permanently installed and fitted for pumpout...which, with the addition of a y-valve and pump, can also be dumped at sea. No plumbing except a vent and pumpout line...no moving parts to maintain...they use so little flush water that it would require an 18-20 gal (US gallons) holding tank connected to a marine toilet to hold as many flushes...and because they must be vented, odor can be prevented. The only downside: EVERYTHING has to go into the tank to be pumped out or dumped.

Btw, Roger is right--stainless is NOT a good choice for waste holding...aluminum is even worse. And Charles..."pumpable" portapotties do not recirculate. Thetford does make a recirculator, but you wouldn't want one as a a gift!
 
Stainless isn\'t such a bad choice!

Interesting comments about stainless steel being a poor choice for holding tanks, especially as some of the better yachtbuilders specify stainless for their holding tanks. I guess you're right that their life may be shorter than plastic tanks. My stainless tank's only 16 years old, so it's probably too soon to say.
 
Re: Holding tanks

For information, our gallons are not derived from the metric units. 1 imperial gallon = 10lbs of water (and = appr. 4.55litres)
 
Re: Stainless isn\'t such a bad choice!

Waste management is an afterthought for most builders...a necessary evil that adds -0- to the value of the vessel, but adds considerably to its cost. So such things as holding tanks are rarely incorporated into the design. As a result "conventional wisdom" has dictated for decades that "boat toilets stink, holding tanks stink worse." Builders rarely if ever do any research into the nature of sewage either...even after two decades of marine sanitation laws requiring tanks or treatment devices her, most are still surprised to learn that urine is so corrosive that salt is almost benign in comparison. They believe that steel is more durable plastic...with some justification, 'cuz just about anything is more durable than the cheap thin plastic tanks sold by most of the marine retailers here. 10-15 years ago, it wasn't that unusual to find steel--even aluminum--tanks that had been installed 10 years earlier still in good condition, 'cuz the durability of a metal tank is definitely related to how much it's used...and till the late '80s, most weren't...and I'll bet yours sees little use too, pvb...which is why it's still in good condition after 16 years. But a metal tank that's in full time use typically springs its first leak in a weld at a seam or fitting within 2-5 years and becomes a collander in an average of 10 years.

So keep an eye on it...if you don't have to use it much, and always rinse it out very thoroughly before the boat sits, you'll prob'ly get several more good years out of it. But the more you have to use it, the fewer good years it has left. If you have access to inspect the inside of it, I'm pretty sure you'll see some significant pitting already.

And if you want to see what urine does to metal, drop a steel screw into a beaker of urine, close up the beaker and leave it for a year. If there's anything left of the screw, it won't be much.
 
Hmmm...

Maybe you should have a quiet word with some of the leading yachtbuilders who specify stainless holding tanks and whose long-term reputations are hugely valuable, companies such as Hallberg-Rassy, Oyster and Farr.
 
Re: Hmmm...

Since the tank failures always occur well beyond any buildier's warranty period, convincing them they're wrong isn't easy...they made up their minds long ago and so aren't interested in facts that fly in the face of what they think they know.

The same is true of some owners. But fortunately for most owners, I'm the only lone voice crying in the wilderness to try and convince 'em...the sanitation industry agrees.

I've known for years that changing builders' "conventional wisdom" doesn't happen overnight...that it's a game of inches. But some progress has been made...at least MOST builders AND owners have come to realize that aluminum ("aluminium" to y'all) is a bad choice.
 
US vs Imp. Gallon ....

1 imp. gall = 1.20095 US gall
= 4.54596 litres

1 US gall = 0.832674 imp gall
= 3.78541 litres

factors above are for direct conversion at same temp.

Above factors are exact as per ASTM Table 1 - Interrelation of Units of Measurement.

So where does .... "(btw, our gallons are 4 quarts, yours are 4 liters...hence the difference between a US gal and an Imperial gallon))" come from .... when in fact a Quart is the division of Imp gall as well .... the same ratio applies.

Under no circumstance has any imperial measure been derived from any metric.

Just want to clear that little error away ....
 
Re: Hmmm...

There's another holding tank material that nobody has mentioned yet, so I will: GRP. I wanted a custom fit tank to maximise the capacity and minimise the space taken up, but to me the cost of a made to measure polypropylene tank was prohibitive so I made my own out of polyester and CSM, lined with cloth and epoxy resin. It cost very little to make as I had materials going past their use by date anyhow and was a fairly straightforward job.

It has been a success thus far - was only installed this season - and is entirely odour free. We'll see how long it lasts, but I'm pretty confident it will be a good long time.

Here it is before and after installation:
tank1.jpg

tank2.jpg


Oh, and to go back to one of Becky's original questions, it's below the waterline and I pump it out with a manual bilge pump similar to a Henderson Mk.V/Whale Gusher. No problems so far and it empties with little effort.
 
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