How much weight and space (and trouble) does a holding tank account for?

Greenheart

Greenheart

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I read recently that boats below about 28ft aren't suitable for accommodating holding tanks. Is that fair comment? Are they more substantial than fuel/water tanks?

Presumably a holding tank is just an area between the pipe from the loo and the hull-outlet, with valves that allow bypass of the tank when it isn't being used?

I'm definitely not toilet-trained, as far as boats go. The prices for expensive systems seems to be jaw-dropping, and the plans for their plumbing look alarming too.

I daresay there's a comprehensive sea-toilet bible, understanding of which prevents anyone in any boat, ever going wrong?
 
Typically you would aim for a minimum of 50 litres capacity to be useful. It is difficult to find that amount of space in a small boat and if you can it is almost certainly not a simple shape and often not in a convenient (forgive the term) place in relation to the toilet. Common places to use are under forward bunks which means they have to be triangular shaped in 3 dimensions and utilise pumps to empty as they will also be below the level of the toilet and waterline. Add up the pumps, valves, change over valves and piping plus a pumpout and it is not difficult to see why it is both complicated and expensive.

Lot easier if you are designing in before the boat is built as you can then use a much simpler gravity based system using regular shaped tanks which can be moulded as opposed to fabricated. There is still a problem of space, but the loo compartment can be laid out to use some dead space behind lockers. Suggest you look at the later Bavarias (and other AWBs) to see how neatly it can be done and it will also help understand how difficult it is to retrofit without major surgery.

At a guess I would think the factory Bavaria system has a material cost of less than £100 over a straight through. My custom made gravity tank in my Bavaria (built before they designed them in) cost over 5 times that and a pumped system would near double that again - and the only sensible place for the tank would be the other side of the boat nearly 4m away, so 4m of sewage pipe running through the bilge and an extra seacock. Not a good solution!
 
You're really bored today, aren't you? :)

I've seen some very small holding tanks - Plastimo used to make one that fitted round the base of a Jabsco loo! I guess the question is "are they large enough to do anything useful?" If you are in a marina, you'll use the facilities block and if you are in open water, you'll just flush directly out. Few marinas have facilities to empty holding tanks, so you really need sufficient storage to hold all the crew's waste products until you get into open water - for most of us, that would imply several days of storage.
 
Tranona said:
the only sensible place for the tank would be the other side of the boat nearly 4m away, so 4m of sewage pipe running through the bilge and an extra seacock. Not a good solution!
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And while lengthy pipe runs should always be avoided, they're particularly undesirable in a holding tank system because you have to pump extra water through to clear them and thus fill up the tank more rapidly. Or you skimp on the pumping to avoid filling the tank, the pipe stays full of sewage most of the time, and you get smells.

The leaky old holding tank in Ariam got ripped out and left in a litter bin (sorry!) shortly before our purchase was finalised. We didn't replace it.

Pete
 
What is the craic with holding tanks anyway. I am of the 28 foot variety and do not have one. My heads simply has a pipe to outside and that is all. When I am ashore I simply use the available facilities and even when not ashore I rarely need the loo as I will be ashore soon. Certainly, not to go into too much detail and being a bloke, off the side of the boat offers a large receptical for number 1s. A holding tank looks like a disaster waiting to happen in an already complicated toilet system. With my simple toilet people still get it wrong and break the bloody valve preventing pump out. I do not fancy dealing with a tank full of carp. I have now taken the principle, bearing in mind the low cost of Jabscos value selection, that if it breaks get a new one! Not worth the hassle and should be considered for emergency use like flares and liferaft! :)
 
The most inconvenient (!) aspect is often the positioning of the control mechanism. It will typically be down at the discharge skin fitting at the bottom (!) of a locker that you want to use to store things. In the marina, we will generally use the facilities block, but I have painful memories of a couple of occasions waking up in the middle of a stormy night desparate for the loo and having to scrabble in the bottom of the saloon lockers to close the valve.
 
pmagowan said:
What is the craic with holding tanks anyway. I am of the 28 foot variety and do not have one. My heads simply has a pipe to outside and that is all. When I am ashore I simply use the available facilities and even when not ashore I rarely need the loo as I will be ashore soon. Certainly, not to go into too much detail and being a bloke, off the side of the boat offers a large receptical for number 1s. A holding tank looks like a disaster waiting to happen in an already complicated toilet system. With my simple toilet people still get it wrong and break the bloody valve preventing pump out. I do not fancy dealing with a tank full of carp. I have now taken the principle, bearing in mind the low cost of Jabscos value selection, that if it breaks get a new one! Not worth the hassle and should be considered for emergency use like flares and liferaft! :)
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That theory works for the day sailor, but not so well for the cruiser. In the marina, we'll use the facilities and in open water it goes straight in, but that still leaves anchorages where it is not really responsible to flush out. We're particularly conscious of it since my wife likes to wind-surf off the boat and does not relish the thought of falling into what is effectively a dilute cess-pit.
 
maby said:
That theory works for the day sailor, but not so well for the cruiser. In the marina, we'll use the facilities and in open water it goes straight in, but that still leaves anchorages where it is not really responsible to flush out. We're particularly conscious of it since my wife likes to wind-surf off the boat and does not relish the thought of falling into what is effectively a dilute cess-pit.
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You might need to have a word with the seals, otters, birds and fish! :) I don't think they got the memo. I suppose if an anchorage is crowded there may be a cumulative effect but you don't have to be too far out from the shore before the dilution rate would be such that the risk is = zero. I suppose a macerating toilet would help, or a curry might achive the same effect! We tend to only be places, even anchorages, overnight and we normally row ashore to go to a pub even if we have to walk a mile or so. I can't remember the last time I needed to use the heads in anger. It is good to have for emergencies though and I understand other people have different styles of sailing so I am only jesting. :)
 
pmagowan said:
You might need to have a word with the seals, otters, birds and fish! :) I don't think they got the memo. I suppose if an anchorage is crowded there may be a cumulative effect but you don't have to be too far out from the shore before the dilution rate would be such that the risk is = zero. I suppose a macerating toilet would help, or a curry might achive the same effect! We tend to only be places, even anchorages, overnight and we normally row ashore to go to a pub even if we have to walk a mile or so. I can't remember the last time I needed to use the heads in anger. It is good to have for emergencies though and I understand other people have different styles of sailing so I am only jesting. :)
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We are river sailors most of the time - the same lump of sewage floats past you four times each day - twice upstream and twice downstream!
 
Thanks for the replies gentlemen. It's not a question I have to face at present, I'm happy to say, but if circumstances should change, it's nice to know the options and pitfalls.

Always pictured keeping any yacht I might own on a swinging mooring in a natural harbour. I wouldn't relish having to row ashore in order to 'sit down', so I'd want holding capacity.

I hadn't visualised the benefit of the tank's proximity to the loo. I suppose if one can weld-together a heavy plastic tank to fit the available bathroom space, it's all possible.

Are macerators essential? I can appreciate that minced-up sewage and paper can be more easily piped, but whatever did yachts do before macerators? Dare I ask? :eek:

I saw a slightly stomach-turning programme which showed that the vast majority of solid human waste in sewer-pipes ashore, quickly takes liquid form. Presumably that's because we also flush a vast amount of perfectly clean water with our waste. Is the dilution process similar on board? I'm always surprised by the narrow little pipes which yacht toilets have, compared with the same systems on shore. Assuming unlimited seawater is available for flushing, is there a good reason for the width-constriction of pipes on board?
 
Don't get too hung up on the idea of a macerator - the pump on a standard marine loo does it just fine! The solid waste out of the toilet bowl gets pumped through a joker valve that will be capable of breaking it up well enough - no complete logs get through to the holding tank!
 
I think the pipes are small because boats are small. For the most part they seem to work fine and I don't think I would want a 6 inch through hull fitting so thee pipe might as well be all the same size. My heads is non macerating but I think a bit of mushing happens when you pump things out. You can pump as much water through as you want but when the kids have left the pool and are out in the big wide world there is not much point in pumping any more. Some people put vinegar and all sorts down the loo to try and reduce smells and I think this is mostly a problem with holding tanks as we don't get any smells that I notice from the loo. Before macerators and heads there was a bucket. Prior to this there was simply a large net over the side which you used as a toilet seat. In fact one of the first reports of hygeine being important came from a naval ship where the captain insisted that the men washed their hands after coming back from the carp net and thus managed to reduce mortality and morbidity on board by a massive amount.
 
pmagowan said:
Some people put vinegar and all sorts down the loo to try and reduce smells and I think this is mostly a problem with holding tanks as we don't get any smells that I notice from the loo.
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Our tankless system is also entirely odourless despite regular use for the full range of functions (well, nobody's been sick in it to my knowledge). The solution is simplicity - a short length of very expensive high-quality pipe (the same stuff forumite jfm used on his baby superyacht over on the Mobo forum) and then out to sea.

Holding tanks don't have to smell, but it must be a bigger challenge to achieve.

As for the history, I think you want this post: http://www.ybw.com/forums/showthrea...he-anchor-oh-yes-indeed&p=4667916#post4667916

Pete
 
My 25 foot boat has a small-ish plastic tank (about 20 litres) inserted into the outlet pipe. It has a air vent, and there is also a (usually closed) opening for cleaning; the base of the tank is above sea level by a few inches. And that's about all the plumbing, If the outlet seacock is closed all the product stays in the tank until the seacock is opened. Adequate for necessary functions while anchored in swimming areas and for midnight emergencies in marinas. Remember to open the seacock when in open water.

Since the plastic is translucent the level is visible. Do not allow to overflow.
 
If you plan to build your own tank, look at using a closed cell foam board/sheet (klegacell) is good, makes for easy construction, using standard resins. make sure all internal corners are will rounded and that the inside is coated with epoxy resin.

The above structure will no sweat like solid fibreglass tanks can and the epoxy ensures no smells escape through the material.

Any external pipe and particularly hoses MUST be rated for raw sewage or the pong will permeate right through lower deck.

Good luck and fair winds. :)
 
This is all most interesting and instructive, thank you gents. I'm not rearranging an on-board loo yet...but my time will come.

oldsaltoz said:
...hoses MUST be rated for raw sewage or the pong will permeate right through lower deck.
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That sounds awful. Wonder what the rated hose is made from?
 
I have had two boats equipped with a Porta-Potti. No problem at all, and cheap enough to replace when necessary. No pipes or sea cocks. No good for the Turkish Grey water rules of course. My present boat has a pump out loo with no holding tank. I am very seriously considering removing the porcelain potty for a Porta-Potti. Not ideal at all but better than pumping out in an anchorage.

Pump out stations are a must in the East Mediterranean. No 12 mile limit for dumping overboard. Twelve miles out from the Turkish coast would be Six miles inside the Greek territorial waters.

How would the Greeks react to hordes of Turkish Charter boats emptying their tanks on the Greek beaches?
 
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