How big a holding tank do I need?

[Burnham_Bob]

Thanks for the previous advice on holding tanks. However, I don't really know how big a tank I need.

Two of us usually, and obviously when sailing (where legal) we'll pump the toilet straight out, in marinas we'll use the local facilities (except at night to avoid the walk!) and grey water will not be collected in the main tank.

Any advice? Once I know the size forumites recommend, I can check size of space available on the boat.

How big would you advise for not being caught short between pump out stations or far enough out cruising in France or Holland to empty overboard?

 

[vyv_cox]

I've owned a holding tank for five years but have yet to use, or even see, a pump-out facility. Our tank is one of the wrap-around type on an RM 69 toilet. This would definitely not be my first choice system but if space constrains there are few other options.

The tank is 25 litres capacity, two aboard. We often anchor in the same place for three or even four nights but we have never filled the tank. We are very frugal about putting flush water into it, e.g. pee is flushed straight over the side and after a few pumps with solids we switch to overboard for the final flush of hoses.

 

[Lizzie_B]

I would go for the biggest you can find space for.
Regulations re where you can pump to sea are likely to get tougher and my experience has been, no matter how big the tank, it always announces itself as full in the most inconvenient place.
The bigger the tank, theoretically, the less often this will happen

 

[bazobeleza]

I concour, we fitted a 85l tank, with both pump out and gravity emptying, and it does indeed fill up faster than you realise, and thats only with two of us.

Fit as big a tank as you get away with.

 

[misterg]

For a 'normal' sea toilet (i.e. not Lavac, not electric, etc.) the Man from Tek Tanks said to allow 2.5 gallons of capacity per person per day (if everything goes into the tank). This could obviously be eked out by careful flushing & use of shoreside facilities.

I think I've found a big enough space for an 80l tank, but just need to find somewhere else for the battery charger... /forums/images/graemlins/ooo.gif

Andy

 

[BobnLesley]

...the Man from Tek Tanks said to allow 2.5 gallons of capacity per person per day...

That sounds about right: We've got a 48 litre tank and wish we could've squeezed a bigger one in; as suggested, it's good for a couple of days which can with care be stretched to three. From our experience I'd say any smaller's a waste of time.

 

[charles_reed]

Fabled pump-outs

in the Med, Bonifacio, le Castella, Varazze.

None worked (I think the Bonifacio one has since been removed).

I too have a RM69 saddle tank, fortunately I seldom have to use it as the changeover valve is a triumph of ingenuity over engineering.

Though it may be alleged to hold 25 litres, you would be ill-advised to fill it fully. It does 2 of us two nights and days.

 

[Ariadne]

Re: Fabled pump-outs

We've got a 60l tank (biggest I could fit) for 2 adults and 2 children. Only found a pump out in Villamoura and I think there may have been one in Almerima. Haven't seen or heard of any since. Never even been asked if I have a holding tank fitted.

Make sure your gravity drain works well, as has been said not many pump out facilities around, and even if you do find one it will be expensive!

So use your head, and use the tank when/where you have to and discharge straight out when you can. Most people we've met use the tank in good swimming areas during the day and let it go overnight when its quiet, never seen solids or paper floating/lying around in the morning yet.

 

[Tranona]

You are unlikely to find space for much over 40 litres - less if you are fitting a pumped system because of all the pipework. Have a look in the Vetus catalogue as there are pictures of different sizes and types of tank to give you an idea of bulk.

If you do go the custom route make sure you have the pick up and fitting for the pumpout installed even if you don't connect it up. As others have said pumpouts are rare, but may become more common in the future.

 

[Tranona]

Should have added that if you are marina hopping and only using it for night emergencies (hopefully limited solids) 40 litres is more than enough, particularly if you have a Lavac which tends to use less water. Mine is 30 litres which is the usual size of the smallest "kit" ones.

 

[AliM]

This summer we saw lots of posters for a very restrictive policy for all inland waters just starting in the Netherlands (inc Waddenzee). The pump out facilities were not that common, that I noticed, anyway. The guidelines I saw made us think 60l was about right for two of us using it for a week. If you aren't going to be in canals, inland seas etc much, then go for a smaller one, though.