Best Marine Composting Toilets (2020 Reviews)

selective photo of a Nature's Head marine composting toilet installed in a boat

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You are here because you have a boat needs a new head or you want info about marine composting toilets. As a buyer, choosing a composting head can be overwhelming, especially if you haven’t owned one. While it might seem like a complicated process, there’s no need to worry, since I reviewed the 4 best models for 2020.

To help you make an informed decision, I have developed this article in two parts. First, you can read in-depth reviews of the top 4 marine composting toilets. Second, I include a buyer’s guide for how to choose a marine composting head.

For ease of use I include clickable table of contents to navigate to a specific product or section. Or, scroll down to learn which composting toilet is best for your application.

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Table of Contents

Comparison Chart

Preview
Editor's Choice
Nature's Head Self Contained Composting Toilet with Close Quarters Spider Handle Design
Villa 9215 AC/DC
Budget Friendly
SUN-MAR GTG COMPOSTING TOILET || Portable Toilet, Compost Toilet for RV
Product Name
Nature’s Head Composting Toilet with Spider Handle
Separett Villa 9215 AC/DC Composting Toilet
Sun-Mar GTG Composting Toilet
Verdict
Absolute Best Liquid Diverting Compost Toilet
Versatile On Or Off-Grid Powered Composting Head
Cheapest Separating 2-Tank Toilet
Shape
Rectangular
Oblong
Oblong
Material / Color
Plastic / Granite
Polypropylene / White
High Density Polyethylene / White
Dimensions (L x W x H Inches)
19 x 17.75 x 21.7
26.5 x 18 x 21.6
24 x 15.75 x 19.8
Solids Compartment Size
60 – 80 Uses
23 Liters Or 6 Gallons
6 Gallons
Liquid Compartment Size
2.2 Gallons
None – Plumb To Holding Tank
1.85 Gallons
Weight (Pounds)
28 (Empty)
36
25
Power Source
12 Volt DC Adapter / 3 watts
DC 12 Volt / 2.5 Watts Plus AC Adaptor
DC 12 Volt / 0.6 Watts
Installation Method
Floor Mounted
Floor Or Wall Mounted
Wall Mounted
Max Weight Capacity (Pounds)
300
330
300
Warranty (Years)
5
5 – Unit / 3 – Fan
Unknown
Editor's Choice
Preview
Nature's Head Self Contained Composting Toilet with Close Quarters Spider Handle Design
Product Name
Nature’s Head Composting Toilet with Spider Handle
Verdict
Absolute Best Liquid Diverting Compost Toilet
Shape
Rectangular
Material / Color
Plastic / Granite
Dimensions (L x W x H Inches)
19 x 17.75 x 21.7
Solids Compartment Size
60 – 80 Uses
Liquid Compartment Size
2.2 Gallons
Weight (Pounds)
28 (Empty)
Power Source
12 Volt DC Adapter / 3 watts
Installation Method
Floor Mounted
Max Weight Capacity (Pounds)
300
Warranty (Years)
5
Preview
Villa 9215 AC/DC
Product Name
Separett Villa 9215 AC/DC Composting Toilet
Verdict
Versatile On Or Off-Grid Powered Composting Head
Shape
Oblong
Material / Color
Polypropylene / White
Dimensions (L x W x H Inches)
26.5 x 18 x 21.6
Solids Compartment Size
23 Liters Or 6 Gallons
Liquid Compartment Size
None – Plumb To Holding Tank
Weight (Pounds)
36
Power Source
DC 12 Volt / 2.5 Watts Plus AC Adaptor
Installation Method
Floor Or Wall Mounted
Max Weight Capacity (Pounds)
330
Warranty (Years)
5 – Unit / 3 – Fan
Budget Friendly
Preview
SUN-MAR GTG COMPOSTING TOILET || Portable Toilet, Compost Toilet for RV
Product Name
Sun-Mar GTG Composting Toilet
Verdict
Cheapest Separating 2-Tank Toilet
Shape
Oblong
Material / Color
High Density Polyethylene / White
Dimensions (L x W x H Inches)
24 x 15.75 x 19.8
Solids Compartment Size
6 Gallons
Liquid Compartment Size
1.85 Gallons
Weight (Pounds)
25
Power Source
DC 12 Volt / 0.6 Watts
Installation Method
Wall Mounted
Max Weight Capacity (Pounds)
300
Warranty (Years)
Unknown

Preview
Top Marks
Nature's Head Dry Composting Toilet with Standard Crank Handle
Product Name
Nature’s Head Dry Composting Toilet with Standard Crank Handle
Verdict
Runner-Up For Best Composting Head
Shape
Rectangular
Material / Color
Plastic / Granite
Dimensions (L x W x H Inches)
22 x 21 x 21.7
Solids Compartment Size
60 – 80 Uses
Liquid Compartment Size
2.2 Gallons
Weight (Pounds)
28 (Empty)
Power Source
DC. 12 Volt Adapter / 3 watts
Installation Method
Floor Mount
Max Weight Capacity (Pounds)
300
Warranty
5 Years
Top Marks
Preview
Nature's Head Dry Composting Toilet with Standard Crank Handle
Product Name
Nature’s Head Dry Composting Toilet with Standard Crank Handle
Verdict
Runner-Up For Best Composting Head
Shape
Rectangular
Material / Color
Plastic / Granite
Dimensions (L x W x H Inches)
22 x 21 x 21.7
Solids Compartment Size
60 – 80 Uses
Liquid Compartment Size
2.2 Gallons
Weight (Pounds)
28 (Empty)
Power Source
DC. 12 Volt Adapter / 3 watts
Installation Method
Floor Mount
Max Weight Capacity (Pounds)
300
Warranty
5 Years

Best Overall Marine Composting Toilets For Sailboats

Purple label with gold anchor stating Editor's choice
Nature’s Head Composting Toilet with Spider Handle
  • Shape: Rectangular
  • Lower Foot Print: Depth - 19 (+1.5 Rear) , Width - 17.75 Inches (+2" Either Side)
  • Material/Color: Plastic With Stainless Steel Hardware / Granite
  • Solids Tank Size: 60-80 Uses
  • Liquid Tank Size: 2.2 Gallons
  • Total Dimensions: 19" L x 17.75" W x 21.7" H
  • Weight: 28 Pounds (Empty)
  • Power Source / Watts: 12 Volt DC Adapter / 3 Watts
  • Install Method: Floor Mounted
  • Warranty (years): 5
What We Like
What We Do Not Like

Nature's Head Compost Toilet (Spider Handle) Review

Let’s start this review by dispelling a common opinion about composting toilets. People who discount them will eventually admit they’ve never used one. Whereas, owners of a “Natures Head” generally say they won’t put in anything else. Why is this? It’s because these marine composting toilets are amazing. In fact its designed by two professional sailors.

The best feature of the Nature’s Head is its capacity. You don’t need to empty it until around 60-80 uses! In real time this equates to a full season of weekend use or around a month for live aboard users. Other great features of this marine head are as follows.

Compact Footprint

The second reason this is an amazing composting head is the small footprint this toilet has. The toilet base has an actual depth of 19 inches and width of 17.75 inches. As a result, most boats big and small will be able to install this toilet. One thing to keep in mind, this toilet is floor mounted and needs wood backing to secure it.

On the side is the great “spider handle.” This gives extra leverage for composting in tight spaces. The spider handle is best for boats that have little room on the sides of the toilet. Whereas the standard handle is best for people with joint issues. At the time the handle gets too hard to rotate it’s time to empty the solids tank.

Durable Materials

Next, to ensure longevity it uses stainless steel hardware and plastic body construction. Users will appreciate the standard seat height and elongated seat shape. Which means you can sit down without feeling like your feet are dangling or squatting on the floor. Another bonus is the attached seat on the unit. This is great because it means there’s no chance of the toilet seat breaking or shattering in rough waters.

I also like the easy-to-use snap latches on the base that give you access to the solid waste container. This is much easier to use than the thumbscrews found on other brands like Airhead. Although, some users might not like that you have to lift the container out instead of sliding it off. On convenient feature is the liquid container comes with a nice carry handle.

For composting with the Nature’s Head, you have two inexpensive options. The solids tank uses either sphagnum peat moss or coco coir, both of which are easy to buy anywhere. In use, single-ply toilet paper is fine for this marine head.

Self-Contained & Odorless

Being a self-contained unit, it uses two containers below the seat to catch the waste. One is for urine and the other for feces, so all composting happens from start to finish inside the unit. To prevent stinky sewage odors, the toilet uses a 12 volt vent fan powered off your boats’ batteries. On the water the fan works well, there was absolutely no odors coming from the solids tank when I used it. However, I do notice a tiny smell from the liquid tank but I fixed this issue with a spray bottle of vinegar/water.

Verdict:

Choose the Nature’s Head with Spider Handle if you want the best composting head on the market. By doing so, you get a hassle-free marine compost head that’s inexpensive, compact and odorless.

Versatile Composting Head For Boats With Holding Tanks

Separett Villa 9215 AC/DC Composting Toilet
  • Shape: Oblong
  • Lower Foot Print: Depth - 26.5 (+1.1 Rear) Inches , Width - 18 Inches
  • Material/Color: Polypropylene / White
  • Solids Tank Size: 6 Gallons
  • Liquid Tank Size: None- Pipe To Holding Tank
  • Total Dimensions: 26.5" L x 18 W x 21.6 H
  • Weight: 36 Pounds (Empty)
  • Power Source / Watts: 12 Volt DC Adapter & AC Wiring / 2.5 Watts
  • Install Method: Floor Or Wall Mounted
  • Warranty (years): 5 - Unit / 3 - Fan
What We Like
What We Do Not Like

Separett Villa 9215 AC/DC Marine Composting Toilets Review

In 2020, the Separett Villa 9215 AC/DC is a great solution for boaters looking to reduce volume in a holding tank. It has a sleek appearance that look modern and clean in any boat. The Villa 9215 is a urine diverting, waterless head with a locking toilet seat. This is great as it prevents the seat from smacking you in rough waves. Capacity for the solids tank comes in a respectable 6 gallon size.

Unique Composting Design

The unique “handle-less” design of the Villa 9215 appeals to many boaters. In use, it has a solids hatch that opens up as you sit down. Then it rotates the waste container when you rise off the seat. By moving the position of the solids tank, compost has a better chance of drying and breaking down.

Next, to reduce volume in your holding tank, it only allows liquids to flow to it. For solids, it uses an integral composting tank to break down the waste. Thus, you can be on the water for longer between pump-outs.

It’s important to separate the urine from the solids to help the composting process. Urine slows composting because it keeps solids wet and cools them. Optimal composting, needs the solids to be warm and dry.

For ease of use, it comes with 10 compostable bags and one inner waste container with a lid.

Versatile AC/DC Power

Beyond the actual plumbing for the Villa 9215, it also has a feature that no other brand has. The Villa 9215 supports both AC and DC power sources, so you can use it both on and off-grid. The AC power allows you to use standard marina hookups when onshore. Or use 12-volt DC power offshore with either your vessels’ battery or solar unit.

Simple Installation

Often installing a marine head can become complicated, not so with the Villa 9215. Right out of the box, it takes little time to install this marine head. The entire unit comes completely assembled and you can either mount it on the floor or a wall. Be aware though, the toilet base is quite deep at 26.5 inches. Plus it needs an extra 1.1 inches behind it to route the vent piping. Fitting this head might be problematic in smaller boats. Especially due to the heavy weight of the Villa 9215, coming in at a whopping 36 pounds.

After you mount the actual unit all that’s left is to hook up the hose to the tank and vent pipe. The instructions for the Villa are simple and concise. For venting, it uses a 20 CFM fan that needs 3-inch schedule-40 PVC piped to the outside. All vent components, less the PVC pipe are in the package with this toilet. Although I should note, the fan does get complaints from owners about being too weak.

Verdict:

The Villa 9215 is an interesting option for boaters that still want to use a holding tank. While it’s not a self-contained unit, it’s a good entry-way into the composting world. My only issues with it are it’s large foot print and complaints of the weak vent fan. If you have room for it and can solve the fan output it’s a good performer.

Inexpensive Composting Head For Low Bulkhead Boats

green budget friendly label
Sun-Mar GTG Composting Toilet
  • Shape: Oblong
  • Lower Foot Print: Depth - 24 Inches , Width - 15.75 Inches
  • Material/Color: High Density Polyethylene / White
  • Solids Tank Size: 6 Gallons
  • Liquid Tank Size: 1.85 Gallons
  • Total Dimensions: 24" L x 15.75 W x 19.8 H
  • Weight: 25 Pounds (Empty)
  • Power Source / Watts: 12 Volt DC Adapter / 0.6 Watts
  • Install Method: Wall Mounted
  • Warranty (years): Info Not Available
What We Like
What We Do Not Like

Sun-Mar GTG Composting Head Review

Calling the Sun-Mar GTG a composting toilet is a bit of a stretch. Yes, it has a liquid/solid separator but composting with this unit is as basic as it gets. The solids tank looks like a household waste bin, which you line with a bag and add coco coir to for slow composting. Another option is to leave out the coco fiber and only use the bag as a porta-potty.

The main reason I included the GTG is for vessels with low bulkhead room, plus it has a tiny price tag. Its a decent compromise between using a traditional porta-potty and a composting head. But make no mistake this isn’t a feature packed model. I like to think of it as a “rustic experience.”

Value Priced Construction

For design, Sun-Mar sticks with a solid thick resin like material in a one-piece sleek design. The company boasts that it’s a “simple and elegant solution for small spaces.” It’s definitely a good solution for low bulkheads as it measures at 19.8 inches in height. The depth and width fall into the middle of the pack of models reviewed.

Weight wise the GTG is the lightest at a mere 25 pounds, which is great for small boats. As I mentioned before, it’s a basic design to help keep costs low, don’t expect to feel like you are “at-home” on it.

For simplicity the GTG exceeds as it has a one-piece unit with a simple fan and vent hose set-up. However, the Sun-Mar instruction manual is best used as waste-paper as far as I’m concerned. The vent fan is a 12-volt DC with a microscopic power draw of 0.6 watts! Keep in mind, some users complain that the fan wiring is too short and fragile though.

The heavy-duty GTG will support a person up to 300 pounds. For capacity, it stores liquids up to 1.85 gallons, and solid sewage up to 6 gallons.

Is The GTG Compost Head Low Maintenance?

By its proposed design, this head should be low maintenance. But in my experience the liquid and solid tanks need improvement. Both tanks sit under the seat but have open tops so liquid and solid sewage can mix. As a result, the composting process gets compromised. Also, if you live in a humid climate this is not the marine head for you. With an open solid waste tank and low powered fan it will never have a chance to dry out and compost.

Picking the GTG is a leap of faith since I couldn’t find any information about a warranty.

Verdict:

If your boat has a low bulkhead that can’t fit a modern composting toilet, then the GTG is a possible solution. It’s better classified as a port-potty with a composting option. Boaters will like it for its simplicity and clean look but will need to except some caveats. The Sun-Mar GTG is for hearty sailors looking to extend the time between emptying.

Runner-Up Best Marine Composting Head For Large Boats

top marks label in blue with yellow check mark
Nature’s Head Composting Toilet with Standard Handle
  • Shape: Rectangular
  • Lower Foot Print: Depth - 19 (+1.5 Rear) , Width - 21 Inches (+2" Either Side)
  • Material/Color: Plastic With Stainless Steel Hardware / Granite
  • Solids Tank Size: 60-80 Uses
  • Liquid Tank Size: 2.2 Gallons
  • Total Dimensions: 19" L x 21" W x 21.7" H
  • Weight: 28 Pounds (Empty)
  • Power Source / Watts: 12 Volt DC Adapter / 3 Watts
  • Install Method: Floor Mounted
  • Warranty (years): 5
What We Like
What We Do Not Like

Nature's Head Compost Toilet (Standard Handle) Review

My runner-up pick in 2020 for best marine composter toilets is the other version of my top pick. This is the Nature’s Head with the standard handle. Choosing this model gets you a robust and dependable compost toilet. One that is simple to install and just works.

The American brand is famous for their marine composting heads. Started by a pair of sailors they have designed a model that fits and functions in a confined space. For peace of mind they offer an awesome 5-year warranty too.

Smooth Agitator Handle

A wider handle means this version won’t be as compact as the “spider-handle” model but it’s not obtrusive. You will need at least 4 inches of space on the side the handle is to turn it. The bonus of this handle is most boater feel its much more user-friendly. Rotating the handle tends to be a bit easier and faster, which is better for kids and people with joint issues.

Superior Performance

As I mentioned in my top pick, Nature’s Head tops all compost heads in performance. They are water-free, odor-free, and liquid diverting. The separate sewage tanks are well-secured and the liquid does a great job of diverting. The liquid bin is 2.2 gallons and the largest of the bunch. To divert the two different types of waste into their bins, you engage a flush handle on the side of the unit.

This model uses 1 gallon of sphagnum peat moss or coconut fiber. After each addition to the solids bin, turn the agitator handle a few times. This mixes the composting bin to create aerobic action. Like my number one pick, expect a sewage capacity of 60-80 uses before emptying the solid bin.

For venting, this unit ships with 5 feet of ventilation shaft and a 12-volt DC fan. The fan is economical as it draws a very small amount of power, around 3 watts or 1.7 amps over 24 hours. In use, it does a great job of keeping bad smells out of the living quarters of the boat.

Verdict:

If you want a Nature’s Head compost head, prefer easy agitation and space isn’t an issue this is the model for you. It has excellent performance built with top-in-class materials. Most boaters choose a Nature’s Head and never look back. Still, not convinced? Rest assured it has a return policy and an amazing 5-year warranty too.

How To Choose Marine Composting Toilets?

Below is a buyers guide for marine composting toilets. First I explain what exactly composting toilets are and how they work. Followed by the types, typical installations and general benefits of these types of toilets for your vessel.

What Is A Composting Toilet?

A composting toilet is a type of dry toilet that separates solid and liquid waste using little to no water. It treats human waste via a biological process called composting. This creates an oxygen-rich environment where aerobic organisms break down the waste.

Composting toilets are good solutions for boats without a space for drainage systems. Alternatively, they are a practical option for use in RV camping or for an off-grid cabin.

It’s important to understand that this type is U.S. Coast Guard-certified and meets all “no discharge” regulations as a Type III marine head.

Types Of Composting Toilets

Composting toilets fall into two categories either self-contained or remote compost systems. They further break down into two types based on their features, these are:

Simple dry composting toilets 

A dry composting toilet uses no water, which is why it’s also called a waterless toilet. This type uses a natural air vent but may use a hand crank agitator to speed up the composting process.

Electric composting toilets 

This type is a dry compost toilet but adds the use of an electric fan to enhance the process. A small fan creates continuous airflow through the ventilation line. Helping to dry out the solids tank and evacuate odors. An electric composting toilets is the best option for marine environments. Power for this type can be from a 12 volt system or through a standard 110v onshore supply.

How Does A Composting Toilet Work?

To use a composting toilet a user must sit down to do their business. Liquids get channeled to a separate tank or to a holding dank downstream of the toilet. For solid waste, it gets diverted into its own tank or bin. This bin can be a part of the toilet unit or a separate composting tank away from the toilet.

Inside the bin, waste mixes with a carbon additive. Such as sawdust, coconut coir, or peat moss. This mixing creates air pockets in the human waste to promote aerobic action. It also improves the carbon-to-nitrogen ratio and reduces potential odor.

To compost with aerobic action, the toilet must establish and maintain the following:

  • The correct moisture level.
  • A balance of carbon and nitrogen.
  • The right temperature.

To create these three factor the toilet uses an air vent, flapper and a carbon additive. As well, some brands use a method of agitating the tank such as a hand crank. Another component most marine composting toilets use is an integral 12-volt vent fan. This helps to keep the compost dry and speed up the process.

Once the liquid bin is full it’s time to empty it. If you are over 3-miles off shore you can dump over board. For boats inside the 3-mile limit it needs emptying at an approved facility, like a marina.

Inside the solids bin, after the waste transforms it should look and smell like regular soil. Empty the bin into a trash bag and deposit in a dumpster or spread it on non-edible plants.

Install Tips For Composting Marine Heads

Mounting composting marine heads is a simple process as long as you have a spot that allows the toilet to fit. Some will mount on the floor and others can attach to the wall. Most use L-brackets to hold the unit in place.

To start, mark the position of the L-bracket(s). Next, drill the needed holes in the floor, and bolt the brackets down. On most toilets there is a port on the compost bin for attaching a vent hose. Depending on the individual toilet, some may provide the option to attach the hose and fan on either side. Now, determine the route for the vent hose. You have two typical choices, either up through the deck or into an exterior locker, like an anchor locker.

After routing the vent, it’s time to power the vent fan. Most fans connect to a 12-volt DC power source, like a deep cycle battery. Some give you the option of both 12 volt DC and 110 volt AC onshore power. Another solution is to retrofit a solar vent fan to pull air through the vent lines. Sailboat owners who convert away from holding tanks often do this.

To complete the installation, fill the solids bin with the appropriate amount of peat moss or sawdust. That’s it, you’re composting head is ready to use.

Benefits Of Composting Toilets For Boats

Are composting toilets worth it? Yes, there are many benefits to owning a composting toilet for your boat. Including:

Marine Composting Head Are Space Savers

Most composting heads are a special design that are a single unit. As a result, it can be easily installed in vessels with limited space. For boats with a holding tank, adding a composting toilet helps to consume less space too. The holding tank will only hold liquid waste which means you don’t need to worry about emptying it out as often.

Composting Toilets Are Waterless

They don’t need any water for flushing waste which will reduce water use onboard. Less water consumption also reduces the amount of wastewater disposal.

Good For The Planet

A marine composting toilet is an eco-sensitive solution to treating human waste. Using natural decomposition to break down solids’ means there are no chemicals involved. Fewer chemicals is great for the environment.

Simple To Use

Beyond sitting on the unit, the system is easy. Without the use of valves, plumbing pipes or holding tanks, there isn’t much to worry about. There aren’t any moving parts to break down.

* The only caveat here is using toilet paper with a composting toilet. You have two choices when it comes to toilet paper:

  1. Use single-ply toilet paper as it breaks down faster in the solids bin.
  2. Have a sealable toilet paper waste-basket to take care of toilet paper. Europeans have done this for years due to their ancient plumbing systems.

Compost Toilets Are Odorless

On many boats with traditional marine plumbing, you might notice a distinct stink. Poor maintained boat plumbing systems are often the culprit. Especially urine caked hoses and holding tanks. With a compost toilet the vent fan takes care of the solids bin while the liquid tank is simple to empty and clean.

Much More Lightweight

Most typical marine heads need holding tanks that can contain around 18 gallons (ca. 68 l) of waste. Whereas a composting toilet might add around 10 pounds of weight until it needs emptying. This is a big weight difference which is paramount on small vessels.

Finishing Up:

All things considered, you can now make an informed choice for the which kitesurf harness is best for you. Whether you have a long/short torso, are male or female and even if you just want a great deal we have you covered. Remember to focus on comfort, safety features, material quality and fit over looks.

Whichever you choose, thanks for allowing Outdoors Informed help you with your research. We love to research, so spend more time out there ripping it up in the waves.

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Last update on 2020-10-21

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