How big for a holding tank?

[FullCircle]

When I bought my Sun Odyssey 35, I deleted the holding tank as it seemed a bit on the small side at 65 litres, and they gave me a credit for it.

As my boat will become my home in the not too distant future, I have to fit one. Further, we intend to go to Holland this year, so it has become an imperative, and I must lose a fair amount of my workshop space for the poobox.

Within reason, I am not really limited to size (under 220 litres) but I wonder what the forum thinks is a good size, and what can be got away with, without seriously inconveniancing yourself.

Further tip and tricks would also be welcome. I have a 'spare' electric flush loo as I hear that is more economicaal with waste water.

Any suppliers recommended in the UK?


Thanks

 

[PetiteFleur]

In the UK the people are Lee Sanitation and Tek-Tanks, also look at Vetus who also do them. Probably others out there as well.
PS In Holland we use a Porta-Potti - you can get a new small one for about £50 on eBay. Perfectly legal in Holland.

 

[Tranona]

65 litres is a common size for everyday use with a small crew. If you want to store your effluent for long periods between pumpouts then of course you can go much bigger. Vetus do standard size tanks up to 390 litres. They also have a range with pumps attached which eases installation if you have the space.

The first decision you have to make is the time you want between pumpouts which determines the capacity. Then a decision whether to have a simple gravity tank, but this will limit capacity simply because there is rarely convenient above waterline space to fit a biggger tank. Usually once you get to the larger and standard size tanks you are into pumped sytems which are much more complex and expensive.

As already suggested the two best sources of information on design and manufacture of holding tanks are Lee Sanitation and Tek-Tanks. They have schematics of different systems and can customise to your specification. Worth talking through your requirements with them.

Personally, I would go for the simplest, cheapest system. I have just installed a 60 litre gravity tank in my Bavaria, which is adequate for a crew of two if you use shoreside facilities whenever you can. You just need to listen to peoples' stories of pumped systems with pipes full of sewage running through the boat to know such things are to be avoided if possible!

 

[V1701]

How big before weight and position of tank when full becomes an issue to consider?

 

[Tranona]

100 litres is roughly 100 kilos. Low down probably not an issue, although may promote a list. Bulkhead mounted clearly more of an issue, not necessarily stability but ensuring it is properly attached.

However, in reality they rarely get filled unless it is a large crew which uses it all the time!

 

[charles_reed]

Black-water holding tank

My 25l saddle tank covers 2 x persons for 48 hours.

As already said it then depends on how many days you require between pump-outs.

If you intend going to Turkey be aware of their pilot-scheme in Mugla province to demand NO discharges, which means you also are expected to store gray-water, between pump-outs.

You'll then need to add 12l/24hrs per person to your storage tankage.

 

[FullCircle]

Charles that is a start 12L/24 hrs/1 Crew.

I was hoping for a week maximum with 2 on board so

12x7x2=168L.

I can do that, but it would need to extend below the waterline, so a pump is necessary.

Does anyone know if there is a manual poo pump available as well as electrical ones, and what are the reliability in the ermm, harsh environment conditions?

I guess I could organise a separate grey tank on the other side of the boat.

 

[Robin]

I don't know the size of our holding tank but with 2 on board we never had a problem up to a week at a time before pumpout, but not used for grey water or for peeing.

Ours was (boat just sold) a S/S tank mounted under a stern cabin bunk and below the waterline. Overboard pumpout was via a Henderson pump, the same type as used on Lavac loos and we didn't have a macerator pump, just the Henderson diaphragm one. We also had a deck pumpout fitting which we never had cause to use.

 

[Tranona]

Charles that is a start 12L/24 hrs/1 Crew.

I was hoping for a week maximum with 2 on board so

12x7x2=168L.

I can do that, but it would need to extend below the waterline, so a pump is necessary.

Does anyone know if there is a manual poo pump available as well as electrical ones, and what are the reliability in the ermm, harsh environment conditions?

I guess I could organise a separate grey tank on the other side of the boat.

If you have a look on the Lee Sanitation website you will see different pumped systems. Manual pumps can be used and you can construct your own system to suit your situation. Electric pumps are used in the "all in one" tanks - see Vetus and Jabsco. You will also need to arrange a deck pump out fitting which can place constraints on where you locate the tank. A Lavac is supposed to be the most economic on water to reduce stored volume and you can also arrange for the same pump to operate the toilet and empty the tank overboard. There are many possible solutions so worth talking to the suppliers.

Suspect you only need to go into the sophisticated and complex systems if you want to be seriously independent of land based facilities for some time. The trend seems to be toward simple gravity systems for cost and reliability reasons.

 

[Norman_E]

If you can do that, then mount the black water tank above the water line and directly below a deck pump out fitting, with alternative gravity discharge to a seacock. Have a separate grey water tank, which can be in the bilges, and pump it out. That way you are not pumping sewage, and grey water can flow in to bilge fitted tanks by gravity. One important point, put filters into the grey water pipes to prevent hair and food debris getting into the grey water tank.

 

[FullCircle]

Suspect you only need to go into the sophisticated and complex systems if you want to be seriously independent of land based facilities for some time. The trend seems to be toward simple gravity systems for cost and reliability reasons.

Thanks Tranona, we intend to spend the first 2 years taking our boat down Europes Inland waterways to the Black Sea, so some degree of sophistication needed I think.


Grey waste into a bilge tank must be the way to go as well

 

[Tranona]

Thanks Tranona, we intend to spend the first 2 years taking our boat down Europes Inland waterways to the Black Sea, so some degree of sophistication needed I think.


Grey waste into a bilge tank must be the way to go as well

In which case think you need to do some research about what facilities are available. I don't know about the German waterways, but there are virtually no pump out stations in the French canal system. From what has been said here, a similar situation exists in the Dutch inland waterways. So, although there is an intention to limit discharge from boats, there is not an infrastructure in place to provide an alternative, such as there is on the UK canal network. Therefore all the holding tank is doing is holding the sewage so that you can discharge it away from marinas etc!

This disconnection between expectation and reality is one of the reasons for confusion. Couple that with the difficulty of installing (particularly retrofitting) tanks in smallish yachts and the result is the compromise that most people achieve.

 

[Bav34]

as well as electrical ones, and what are the reliability in the ermm, harsh environment conditions?

Our system has a diverter switch in the heads so that we either pump out to sea or into the holding tank. (Some Bavarias pump automatically into a tank and you have the option to close the seacock or not.)

The holding tank is then pumped out either through the deck fitting or using a SeaLand T-Series Macerator and Discharge Pump.

http://www.leesan.com/bundles/041_t_pump.pdf

This has worked fault free for 9 years but I recently managed to destroy one of the 'duckbill' valves by operating the pump with the seacock closed!

Lee Sanitation were really helpful and have a great website.

http://www.leesan.com/

Just an afterthought ... try to get a tank with a top mounted (accessible) inspection hatch. Should the outlet ever block ... which it can do as the solids settle ... it gives you a fighting chance to pump the tank out manually and then have a good rod around (oh joy)

We have some friends who have the inspection hatch two-thirds up from the bottom. When the tank filled, then blocked it was NOT FUNNY.

Amazing what you can do with a wire coat hanger and a dinghy )

 

[V1701]

In which case think you need to do some research about what facilities are available. I don't know about the German waterways, but there are virtually no pump out stations in the French canal system. From what has been said here, a similar situation exists in the Dutch inland waterways. So, although there is an intention to limit discharge from boats, there is not an infrastructure in place to provide an alternative, such as there is on the UK canal network. Therefore all the holding tank is doing is holding the sewage so that you can discharge it away from marinas etc!

This disconnection between expectation and reality is one of the reasons for confusion. Couple that with the difficulty of installing (particularly retrofitting) tanks in smallish yachts and the result is the compromise that most people achieve.

Exactly, so what happens when the black water tank is full and there's nowhere to get rid of it?

 

[ironmaiden]

This holding tank issue is going to become world wide in a very short space of time, and I think the main problems that are going to occur are the lack of pump out stations until all systems are put in place, which is going to take years, but in the mean time it’s going to be looked upon by the local authorities of where ever you are, as a means to make money by fining people,

I’m fitting two holding tanks into simunye, a 175 lt main holding tank which is as low in the hull as I can get it, and a smaller 75 lt tank quite close to the bigger one, the smaller one is going above the water line in the heads this is the one that we will mainly use as it will discharge via gravity. But I’m plumbing the tanks in so that we have the option of using different combinations of use, and with some thought we are managing to get all this in to 33footer.

We will be able to discharge direct to sea or to the large holding tank via the smaller gravity one should we need more capacity such as for grey water, but they will be independent of each other if we wish, this will give us much more flexibility depending on what the local regulations are at the time. This does mean more plumbing, valves etc (all of which are going to be very accessible) but in the long run will be worth the effort, I hasten to ad that we are building from scratch so it’s not being done retro’ and that’s makes it much easier.

Regards Rachel.

 

[Saguday]

Saguday has a 208litre holding tank below waterline. There's a deck pumpout which we always used (in the US whilst not ubiquitous there is usually somewhere not too far away to get a tank pumpout, usually for about $5-10) and an overboard discharge via a pump and a macerator which we never used.

This size tank was fine for a family of four liveaboard and with the usual mix of anchoring and stops ashore we could go a couple of weeks between pumpouts. Grey water didn't go into the tank though although there's still plenty of space for another small tank for grey water if needed in the future.

Trick with holding tank pump outs is to pump out the first lot, then flush with fresh water and then pump out again. In the US the pumps were often on timers so you had to be pretty slick to get it all done before forking out another fiver.

Use Odorloss generously It Is Your Friend.

Having lived for some time with these systems despite the odd problem we are now as a family very uncomfortable with the idea of pumping directly into the sea. Kioni doesn't have a holding tank but I may put a small one in to cope with day/weekend trips if I can only find the space.

 

[V1701]

I think if it comes to having to have a means of collecting grey water I will put a standard 25 litre jerry can strapped in place under the galley & heads sinks with piping and diverter valves so I can choose whether to discharge the grey water or have it flow into the jerry can, cheap & should work? Throwing around 25 litre jerry cans and the 21 litre tank from a Porta Potti will help to keep me fit. I don't have the money or the inclination to do anything else yet, at least until there are more pumpout facilities...

 

[samwise]

Charles that is a start 12L/24 hrs/1 Crew.

I was hoping for a week maximum with 2 on board so

12x7x2=168L.

I can do that, but it would need to extend below the waterline, so a pump is necessary.

Does anyone know if there is a manual poo pump available as well as electrical ones, and what are the reliability in the ermm, harsh environment conditions?

I guess I could organise a separate grey tank on the other side of the boat.

The below waterline factor does, as you say, dictate the need for a pump. Although it might require a radical change to your arrangements, I would recommend fitting a Lavac loo which can be plumbed to deliver a range of options. My Lavac , plumbed in with two diverter valves offers the following options:

Pump Direct to sea
Pump to holding tank ( This can be selective i.e. Pee to sea , solid stuff to tank)
Pump out holding tank to sea

In addition I have a pipe that runs from the tank to a deck fitting so that a marina pump out can be used.

I researched various options and this provided the best range.
The other advantage is that the Lavac (properly installed) is a very efficient and very simple system and a lot more durable than other marine loos)

Tek Tanks who built our custom 84 litre tank and Lavac were very helpful in giving advice on the system and installation.