How Big of a Holding Tank do I Need for my Boat?

holding tank for my boat

I always had a doubt – While purchasing a boat, how many people take into consideration the holding tank’s size?

It is important and you should consider it while buying a boat. Although there is no rule of thumb concerning a boat’s holding tank, there have always been arcane and numerous attempts to create a basic one.

The condition, which comes down to 99 percent most of the time, is the required space that you should make sure a boat should have where you can put at least one holding tank.

As a standard, in this article, I give my recommendations based on the size of the boat.


Size of the boat vs. the size of the holding tank!

  • If the size of the boat is under 30 feet, you should consider having a holding tank of minimum capacity of 12 gallons and a maximum capacity of 20 gallons.
  • If you are planning to get a boat that is bigger than 30 feet but less than 35 feet, you can go for a holding tank with a minimum capacity of 20 gallons and a maximum capacity of 30 gallons.
  • In case you are planning to buy a boat that is bigger than 30 feet but smaller than 40 feet, you should consider that the holding tank is of a minimum of 30 gallons.
  • And, if you are planning to buy a boat that is bigger than 40 feet, you should make sure that it comes with a holding tank that has a limit of at least 40 gallons.

The above-mentioned points are suggestions and many other variables will decide the size of the holding tank. As you would agree not all people are the same and similarly, not all toilets are the same.

Nevertheless, the above suggestions will help and provide you a basic understanding of the holding tanks. It is always a wise idea to go for bigger tanks. Smaller tanks can be problematic, but nobody ever complained of a holding tank for being too big for them!

At the same time, you would not like spending too much on holding tanks, so you will try to get the right size. There are many other factors that you should keep in mind before deciding the size of the holding tank.

Have a look at a few important points that will help you in deciding the size of the holding tank. 


Important factors

Electric macerating and vacuum heads are capable of drawing off the system of onboard pressurized freshwater offer one to three quarts per flush. On the other hand, the manual toilets can use almost a gallon of water per flush if it can be pumped for enough time to rinse out the sewage completely of its head discharge line!

There are some ideas that you can use of cutting down on that. One of the clever ways to do that is by rinsing out the line at least once daily. You can try this instead of wasting water by pumping it through every time you flush. However, in any case, it will give you an average of half a gallon or maybe slightly more, whether it has a diaphragm pump or cylinder or piston pump.

An electric macerating toilet that has integral and raw water intake pump needs one to three gallons for every flush. This is because there is no way you can switch to a ‘dry bowl’ without affecting the impeller in a bad way in its intake pump. Few brands come with separate motors that can cut the consumption of water considerably.

However, you still need to make sure that you have enough water to run through it to clear out everything out of its pump or macerator unless you don’t mind dealing with clogs. If the tank is far from the head, you have to flush it for a longer period to make sure that the contents of the bowl are moved to the tank from the head.


In this article, we elaborated on how the size of the boat is important and how you can choose the size of the holding tank based on the size. Further, you have read about the kinds of toilets and every important fact related to them.

Lastly, as we said earlier – nobody complains about a holding tank for being too big! So, all you have to make sure is that you don’t buy a holding tank that is too small!


I'm Wayne, owner of I'm a father of 2. I love reviewing products and showcasing the very best in my best of review lists. I want people to make an informative decision by going through these reviews before purchasing their selected products.

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