Composting Toilet Like a Normal Toilet – How Close Can You Make It?
Composting toilet feels like like an unwanted alternative for many of us, understandably. But does it have to be that way? The answer is: totally not! Modern composting toilets can be made very much like a regular toilet, just without water. In this article we share advices how to make a composting toilet as normal toilet as possible.
1. Choose a Porcelain Toilet Pedestal
To make a composting toilet as close to a regular flush toilet, you have got to use a special porcelain toilet pedestal designed specifically for waterless toilets. The special porcelain toilet is very elegant and feels just like a regular toilet. The only difference is that the waterless porcelain toilet is not flushed after use. That said, the dry porcelain toilet can easily be kept clean with a conventional toilet brush and a little bit of water for example from a water bottle or bidet.
2. Hidden Composting Unit Under Floor Level
The secret to a modern composting toilet is to use an external composting unit under the bathroom floor level. This design makes the waste fall straight into the composting unit from the porcelain toilet through a vertically straight waste pipe. One of the many advantages of this set up is that there rarely ever is clear visibility into the waste from the toilet above – unless you point out the waste with a torchlight.
3. Ventilation for the Composting Unit
One of the most important features of any composting toilet is effective ventilation. This typically involves installing a vent pipe that runs from the composting unit along the back wall of your house or restroom building. The ventilation should be assisted by an electric fan whenever electricity is available. If not, a Whirlybirdwind-driven ventilator or a Solar Panel Fan are excellent alternatives.
Proper ventilation ensures that any odors are immediately drawn out of the composting unit while youβre still using the toilet. In fact, the compost is typically nearly odorless by itself, thanks to the way excess moisture is separated from the solids. With proper ventilation, even faint odors are immediately carried outside.
Living off-grid with a composting toilet is not complicated. In fact, using a composting toilet is almost exactly like using a regular flush toilet. We encourage designing and decorating your bathroom to look and feel just like any other β comfortable and familiar.
In most cases, you wonβt even need to leave special instructions for guests, especially when using a porcelain toilet pedestal. Since there are no moving parts to operate, there’s no risk of anything being used incorrectly or broken.
Showering in the same bathroom is no problem either. Just be mindful not to use an overly powerful bathroom exhaust fan, as it could potentially reverse the airflow from the composting toiletβs ventilation system. With the right setup, a composting toilet can be just as user-friendly and intuitive as any standard toilet.
5. Consider Upgrading to Urine-Diverting Toilet
A urine-diverting toilet(often called a UD toilet) is an optional upgrade to a standard non-diverting porcelain toilet. UD toilets arenβt always necessary, since many composting units are already designed to separate excess moisture from the solids. However, there are situations where a UD toilet is especially beneficial.
For example, if thereβs no electricity to power a fan that helps airflow and evaporation, a UD toilet ensures the composting unit stays dry. Since most odor issues come from compost thatβs too wet, this can be a simple way to maintain a consistently low moisture level and keep everything odor-free.
Because the UD toilet manages moisture so effectively on its own, youβll often need less dry bulking material, which means the composting unit can handle more waste before reaching capacity. This extends the time between servicing.
Itβs worth noting, however, that around 80β90% of human waste volume is liquid urine. This means a UD toilet will produce more separated liquid that needs to be managed, compared to a non-diverting toilet.
If you want your composting toilet to look and feel just like a regular bathroom, itβs worth paying attention to the overall interior design. Choose bright white tiles or other light finishes, add thoughtful lighting, and include the usual bathroom accessories such as a mirror, towel racks, and a small cabinet.
All these familiar touches work together to create a space that looks and feels like any standard bathroom. With a porcelain composting toilet, the setup blends in naturally β making it nearly indistinguishable from a traditional flush toilet environment.
7. Regular Cleaning is the Same
All toilets need regular cleaning β and composting toilets are no different. A waterless composting toilet can be kept clean just like a standard toilet, using a toilet brush and a bit of water. The water source can be as simple as a spray bottle or a small container with a nozzle.
Just be careful not to pour large amounts of water into the composting unit on a daily basis. Remember, a composting toilet is intended to be kept mostly dry β thatβs why theyβre often called dry toilets. Keeping excess water out ensures the composting process stays balanced and odor-free.
Conclusions
As you can see, a composting toilet can be made to look and function remarkably like a regular toilet β just without the water. By choosing a porcelain toilet pedestal, hiding the composting unit beneath the floor, ensuring proper ventilation, and paying attention to interior design, you can create a bathroom that feels completely normal and comfortable.
Daily use and cleaning are virtually the same, and optional upgrades like urine-diverting toilets can make the system even more efficient and odor-free. With the right setup, most people wouldnβt even notice theyβre using a composting toilet.
If youβd like personalized help finding the best composting toilet system for your project, donβt hesitate to contact us at Waterless Toilet Shop.
After years of consideration, this composting toilet was the solution. Instead of adding expense and time for a pool side bathroom, we constructed an adorable outhouse with the Green Toilet in mind. Added a solar powered exhaust fan to make the trips as comfortable as possible. We enjoy the novelty of it all and the unit is very clean with no odors.
We bought a property with a small cabin on it with a composting toilet. It was terrible! Lots of trouble, stinky etc. So I went on the hunt for a new one and found the GL90. I had my handyman install it. Actually we added a separate room on to the cabin. It turned out really cute. And the GL90 fits right in. Looks sleek and NO TROUBLE and no stink!!
We bought a 100 year old cabin with no running water and needed and indoor solution. Wife said she wouldn't stay there until she didn't have to make her way to the privy in the middle of the night.
So, after tons of research on all sorts of composting toilet models, we settled on the GL90. Since we are able to access the crawlspace below, it made sense to choose a model that gets the "mixing tub" out of the bathroom and down below. We went with installation option #2 (only seemed appropriate since it is a toilet!).The result is a toilet that looks like a toilet. And, the porcelain pedestal feels just like a traditional toilet.
Installation was straightforward and simple with the exception of the plastic tabs that the bowl gets screwed into to lock it in place. Took a few times to get it all lined up and did end up taking the oscillating tool the tabs, but it all came together and is nice a secure.
To power the fan, I added a dedicated switch powered outlet so there's never a doubt if the fan is on or not. Mounted the outlet out of the weather underneath the cabin.
I just purchased a Green Toilet 100 EZ for use on our yacht club's island. Setup was easy and the urine diverting feature a plus. The yacht club sailors, especially the women, are thrilled to have this for use before a race.
I have some property off the grid. I needed waterless toilet, and I couldnβt have picked a better one! It was easy to set up, easy to use, and doesnβt smell. Even my very high maintenance kids are excited to use it!
To anyone wanting to get more sustainable by using composting toilets, you will not regret working with Eemeli Palo at Waterless. He has the best customer service in a private company. I would put his customer service right up there with Costco. Not only are their products and prices SUPERIOR, his work ethic is top notch. Do yourself a favor and buy through him. You will save money, time, effort, and any headaches with Eemeli and his company. If I could give him 6 stars I would. This is my first time using this type of product and I look forward to it. I bought the GL-90. Have a great day.
We are off grid and wanted a composting toilet so we could use use huminor for our gardens. The installation was very easy and it works great. The toilet looks great in our bathroom, we are still finishing our cabin but we love this composting toilet. I did some research before purchasing and we are definitely not disappointed. Thank you Waterless toilet.
The Green Lux toilet arrived and was very easy to set up. We built an elevated outhouse to make storage of the containers easy. We hosted a large gathering of 100+ people, and had several tell us that it was the most luxurious outhouse they have ever been in! Also, when the fan went out and the seat got cracked, they didn't even ask questions, and simply sent us new ones! We will 100% be returning customers!
We have been using composting toilets for over 25 years, 1 in our home, 2 in our holiday accomodation buildings, and 1 as an outside toilet.
Green Loo GL 90 is by far the best of all the systems we have used, and I do not hesitate to recommend this system to anyone considering a composting toilet.
It is great value for money, easy to install and maintain, with great customer service. Thank you Green loo for making our lives better!
I have a tiny home in Virginia that needed an upgraded bathroom. I spent a long time investigating composting toilets online and watched a lot of YouTube videos explaining how each works. I knew from experience that separating urine from solids was important for keeping the composting process odorless. The only toilet design that made sense for carefree emptying and separating was the Green Loo. Also, I didnβt want a plastic toilet but an attractive ceramic one. I decided on a Green Loo CF-4 continuous composting system. But how to get it to the East Coast? I decided it was worth paying several hundred dollars in shipping to get the Green Loo, which is only sold in the U.S. in Nevada, to the East Coast.
The toilet arrived on a huge truck that wasnβt willing to come down my dirt road and driveway, so a neighbor ended up picking the box up at the main road in his front end loader and dropping in my yard. I had a builder install it and, and despite some cussing and finessing, he got it hooked up and working in a day; some small parts (bolts and such) had been lost through a hole in the shipping box. (It wasnβt packed well for long-distance shipping). I am very pleased with the quality of the toilet, and the split systemβs heavy duty plastic tank under the floor is sturdy and well made. I could tell it had been banged around a lot in shipping and aside from a few scratches it had arrived unscathed.
I used the Green Loo for a month without the fan to see if I needed it. The system worked in the sub-freezing weather; however, there was a slight odor, so I had the builder hook up the fan that came with it. Now itβs totally odor free. I plan to get the solar panel to run the fan, which is very quiet. The unit comes with a bag of Bokashi, and I ordered more Bokashi on Amazon to jump-start composting. I am using peat moss as a composting medium, but plan to switch to the more sustainably harvested coco coir. The CF-4 model is an excellent product.
Installed our GL 90 compost toilet in our small cabin. It pretty simple, just remember measure twice before cutting.
The Wife and I used it for 1.5 months before I decided 5o switch the waste tank out.
I was not sure what to expect, the waste container is under the cabin. I lifted the lid just pulled it out. There was no smell no excess liquiods.
It was a very simple swap.
We installed the Green Loo 90 in our tiny house build and we couldnβt be more pleased with the final product. Because we live in a very cold climate, we had to do a creative installation to account for our extra thick floor insulation, but Eemeli at GreenLoo was incredibly helpful and gave us some great suggestions. Weβre very impressed with the quality of the components and the ease of installation. When we needed a toilet seat replacement due to an overzealous delivery guy, Eemeli was right there to the rescue and had a new seat to us within a few days.
We cant recommend GreenLoo enough. it's a great product from a wonderful company with absolutely amazing customer service.
After a great deal of research, I decided on the Green Toilet Lux 120 Composting toilet for my off grid cabin. The fact that I could install a replaceable bin under the cabin's "in-house" toilet area was fantastic. The porcelain toilet is a perfect amenity - although I had to find a toilet seat to replace the one that was sent (cracked in shipping - but WTS reimbursed me to cover the costs). A rubber boot on the roof helps to keep rain out of the structure. The wind-driven fan works really well and helps keep the area ventilated. I keep a bucket full of wood mulch in the toilet area and drop 1 to 3 scoops after each use. I found some biodegradable detergent from Dr. Bronners that I mixed with water to spray down the toilet for cleaning at the end of our weekend visit. I also upgraded the provided vent pipe to a 4" pipe.
Having a usable composting toilet in the winter makes our cabin so much more habitable. Thanks for making this product availalbe!
We have been building a small, off grid hut/cabin on our Utah mountain property. We were looking to build something small, simple and low maintenance. Our power is all 12 volt solar and we carry in water. This cabin will be seasonal (no septic)so the toilet had to be simple too. Other composting toilets have too many moving parts and a low capacity. After much research we decided on the GreenLoo GL90. I love the low profile composting bins. We decided to build an attached mechanical room/outhouse/shower room and built it to suit the toilet specifically. The GL90 porcelain toilet is tall and easy to keep clean. I ordered the 12v vent fan with my kit and it works perfectly NO smell at all! I turn off the solar when we leave so I was concerned it would smell upon our returns. So far so good! We are going to install a βwhirlybirdβ wind activated vent cap to vent in addition to the electric fan while we are away from the cabin. Install of the GL90 was a breeze and it looks great! Big thanks to the good folks at The Waterless Toilet Shop for their friendly support and expertise.. and a full line of supplies and accessories! Iβm adding some photos of the Toilet and build so far!
Our Customer Service team is currently on holiday until January 5th, 2026.
In urgent matters, please email us at info@waterlesstoiletshop.com
Thank you for your patience and support. Happy New Year 2026!
Waterless Toilet Shop β Black Friday & Cyber Monday Campaign Terms and Conditions
Campaign Period
This Black Friday & Cyber Monday promotion (βCampaignβ) runs from November 17, 2025 through December 1, 2025 (Cyber Monday). All qualifying orders must be placed during this period. No retroactive discounts will be applied to orders placed before or after the Campaign Period.
Eligibility
The offers are valid only for purchases made on waterlesstoiletshop.com or through direct communication with Waterless Toilet Shop during the Campaign Period. Discounts apply to new orders only.
Campaign Offers
The following products include fixed discounts during the Campaign Period:
$100 OFF all Green Toilet Lux composting toilet packages
$100 OFF CF 4 composting toilet systems
$100 OFF Oz-e-Pod composting toilets
$1000 OFF Rota Loo 650 composting toilets
All other products: price reductions may be available. Customers must request a quote during the Campaign Period to receive the best possible offer.
Discounts are automatically applied to listed sale prices or will be reflected in quoted pricing (as applicable).
Limitations
Discounts cannot be combined with any other promotions, coupons, or discount codes unless explicitly stated.
Discounted pricing applies per product, not per order.
Limited inventory: discounts apply only while stock remains available. Some products may have extended lead times.
Shipping costs are not discounted unless otherwise stated.
Request-A-Quote Items
Products requiring a custom quotation must be requested during the Campaign Period. Quotes provided as part of the Campaign will remain valid for 7 days unless otherwise specified.
Payment & Order Completion
To secure the campaign pricing, full payment or an agreed deposit must be received within the quote validity period. Waterless Toilet Shop reserves the right to void quotes not paid within the specified timeframe.
Cancellations & Returns
Standard return and cancellation policies apply. The campaign discount is non-refundable and will not be βreappliedβ to replacement orders outside the Campaign Period.
General
Waterless Toilet Shop reserves the right to:
modify or withdraw this Campaign at any time,
correct pricing errors,
limit quantities per customer,
decline requests that do not meet eligibility criteria.
By placing an order during the Campaign Period, customers agree to these Terms and Conditions.
Our phone customer service is closed today.
Email customer service remains available β please contact us at info@waterlesstoiletshop.com
, and weβll get back to you as soon as possible.
Thank you for your understanding.
Pay with Klarna
Weβre excited to now offer Klarna as a payment option at Waterless Toilet Shop!
Choose how you want to pay β all at once or with flexible installments that fit your budget.
πΈ Pay in 4 β Interest-Free
Split your composting toilet purchase into four equal payments every two weeks.
No interest, no hidden fees β just a smarter way to pay over time.
Other Flexible Options
Klarna also offers monthly financing with 6β24-month plans and transparent APR rates based on your credit.
Youβll see all available payment options instantly when you select Klarna at checkout.
Klarna financing is issued by WebBank and available to eligible U.S. residents in most states.
Missed payments may incur late fees. For California residents, loans are made or arranged pursuant to a California Financing Law license. Review Klarnaβs terms.
The CF 8 is a continuous composting toilet system featuring a single large 250-gallon container. Like the CF 4, it is designed for gradual emptying rather than batch-style use. Solids are typically removed in thirds or sections, allowing earlier deposits time to fully compost inside the tank.
This setup allows for either:
Year-round use with gradual emptying, or
Seasonal use (e.g., 4β5 months/year) with full emptying once per year
π Continuous Use: Gradual Emptying in Thirds
When used year-round, the CF 8 is typically emptied one-third at a time, effectively composting in three rotating βpilesβ within the container.
Because the CF 8 is more than twice as large as the CF 4, each pile can hold approximately 480β960 poops, depending on composting conditions and how much bulking material is used.
Service Interval (per pile)
Estimated #2 Visits per Day
30 days (1 month)
~17β32 visits/day
60 days (2 months)
~8β16 visits/day
90 days (3 months)
~5β11 visits/day
180 days (6 months)
~3β5 visits/day
365 days (1 year)
~1.2β2.6 visits/day
π‘ These figures assume that one-third of the tank is in active use at a time, with older waste given time to compost before removal.
π€ Seasonal Use: Full-Tank Emptying After Inactive Period
For cabins, cottages, or other sites used seasonally, the CF 8 can be used for a few months and then left idle to allow full composting. In such cases, the entire tank may be emptied once a year.
Full-tank capacity estimate: ~1,440β2,880 poops
Example: 120 days of use (approx. 4 months): β ~12β24 solid visits per day on average
β οΈ Disclaimer
These numbers are rough estimates based on typical use and conditions. Actual capacity will vary depending on:
Climate (temperature and humidity)
Ventilation and air flow
How much dry bulking material is added
User behavior and emptying practices
For best performance, ensure proper aeration, regular bulking material use, and consistent emptying of composted portions.
π‘ Want to Maximize Capacity? Consider a Urine-Diverting Toilet β With Some Important Considerations
If you’re looking to maximize the capacity of the CF 8 system β aiming for 960+ poops per composting βpileβ β we recommend using aurine-diverting (UD) toilet pedestal.
β Benefits of Urine Separation:
Reduces or eliminates the need for dry bulking material, which frees up valuable space in the composting unit
Helps keep the compost drier, more aerated, and better suited for natural decomposition
Increases the total capacity of the composting container
Can lead to faster and more efficient composting, especially in high-use environments
By diverting urine out of the solids container, the volume taken up by absorbent material (like peat or wood shavings) is significantly reduced. This can make a big difference in how often the system needs to be emptied.
β οΈ Downsides to Consider:
Urine-diverting toilets can take some time to get used to. Users need to sit or aim correctly to ensure proper separation, which might not happen consistently without experience or guidance.
For this reason, UD toilets are generally not ideal for public or commercial settings where the toilet is used by guests, tourists, or other first-time users. In these cases, misuse can reduce the effectiveness of the system and may even lead to unpleasant maintenance issues.
In short: A UD toilet is an excellent choice for maximizing capacity in private or family use, but for guest or public access composting toilets, a standard non-diverting model may be more practical and user-friendly.
π $100 OFF Shipping Cost β Green Toilet 330 Composting Toilets
No promo codes, no extra steps β the discount is automatically applied at checkout.
If you experience any technical issue and the discount does not apply automatically, you can manually enter
the coupon code 100OFFSHIPPING during checkout to receive the offer.
The Green Toilet 330 and Green Toilet Lux 330 are ideal for cabins, cottages, off-grid homes, and other locations where
reliable, low-maintenance, and environmentally friendly waste management is a priority. Their batch composting design
makes servicing simple and hygienic, with a spare container included to keep the system running without interruption.
Campaign details:
Offer valid until August 31, 2025 or while stock lasts
Discount applies only to Green Toilet 330 and Green Toilet Lux 330 composting toilet orders
Automatically applied at checkout β or use coupon code 100OFFSHIPPING if needed
Applies to orders shipped within the Lower 48 states only
Upgrade your off-grid toilet system now and save on shipping while supplies last.
Green Toilet 100 Easy β Estimated Daily Capacity
The Green Toilet 100 Easyis a compact and user-friendly batch composting toilet with a 26-gallon composting container. Its design makes it well-suited for outhouses, cabins, and even indoor use. A spare containeris available to expand capacity and simplify servicing.
Note: Due to the shape and internal structure of the container, the actual composting capacity is slightly lower than its raw volume might suggest, if you compare with Green Toilet 120 Family composting toilet for example.
π Average Daily Capacity per Bin
Service Interval
Estimated #2 Visits per Day
30 days (1 month)
~6β7 visits/day
60 days (2 months)
~3β4 visits/day
90 days (3 months)
~2.2 visits/day
180 days (6 months)
~1.1 visits/day
365 days (1 year)
~0.5 visits/day
Notes & Recommendations:
For seasonal or weekend use, one container often lasts a full summer.
For more frequent use, we recommend the package with a spare container. This allows one bin to rest and compost while the other is in active use.
Donβt forget to add dry bulking material (like wood shavings or peat) regularly to maintain airflow and prevent odors.
β οΈ Disclaimer: These estimates are intended as general guidance. Real-world performance may vary depending on:
The CF 4 is a continuous composting toilet system featuring a single large 105-gallon container. Unlike batch composting systems (such as the Green Toilet models), the CF 4 is designed for gradual emptying β solids are typically removed in thirds or sections, allowing earlier deposits time to fully compost inside the tank.
This setup allows for either:
Year-round use with gradual emptying, or
Seasonal use (e.g. 4β5 months/year) with full emptying once per year
π Continuous Use: Gradual Emptying in Thirds
When used year-round, the CF 4 is typically emptied one-third at a time, effectively composting in three rotating βpilesβ within the container. Depending on composting conditions and how much bulking material is used, each pile can hold approximately 200β400 poops.
Service Interval (per pile)
Estimated #2 Visits per Day
30 days (1 month)
~7β13 visits/day
60 days (2 months)
~3β7 visits/day
90 days (3 months)
~2β4 visits/day
180 days (6 months)
~1β2 visits/day
365 days (1 year)
~0.5β1.1 visits/day
π‘ These figures assume that one third of the tank is in active use at a time, with older waste given time to compost before removal.
π€ Seasonal Use: Full-Tank Emptying After Inactive Period
For cabins, cottages, or other sites used seasonally, the CF 4 can be used for a few months and then left idle to allow full composting. In such cases, the entire tank may be emptied once a year.
Full-tank capacity estimate: ~600β1,200 poops
Example: 120 days of use (approx. 4 months): β ~5β10 solid visits per day on average
β οΈ Disclaimer
These numbers are rough estimates based on typical use and conditions. Actual capacity will vary depending on:
Climate (temperature and humidity)
Ventilation and air flow
How much dry bulking material is added
User behavior and emptying practices
For best performance, ensure proper aeration, regular bulking material use, and consistent emptying of composted portions.
π‘ Want to Maximize Capacity? Consider a Urine-Diverting Toilet β With Some Important Considerations
If you’re looking to maximize the capacity of the CF 4 system β aiming for 400+ poops per composting βpileβ β we recommend using a urine-diverting (UD) toilet pedestal.
β Benefits of Urine Separation:
Reduces or eliminates the need for dry bulking material, which frees up valuable space in the composting unit
Helps keep the compost drier, more aerated, and better suited for natural decomposition
Increases the total capacity of the composting container
Can lead to faster and more efficient composting, especially in high-use environments
By diverting urine out of the solids container, the volume taken up by absorbent material (like peat or wood shavings) is significantly reduced. This can make a noticeable difference in how often the system needs to be emptied.
β οΈ Downsides to Consider:
Urine-diverting toilets can take some time to get used to. Users need to sit or aim correctly to ensure proper separation, which might not happen consistently without experience or guidance.
For this reason, UD toilets are generally not ideal for public or commercial settings where the toilet is used by guests, tourists, or other first-time users. In these cases, misuse can reduce the effectiveness of the system and may even lead to unpleasant maintenance issues.
In short: A UD toilet is an excellent choice for maximizing capacity in private or family use, but for guest or public access composting toilets, a standard non-diverting model may be more practical and user-friendly.
(Based on approx. 356 uses involving a #2 β i.e., poop) – only the solids count!
Service Interval
#2 Visits per Day (involving a #2)
30 days (1 month)
~11.9 visits/day
60 days (2 months)
~5.9 visits/day
90 days (3 months)
~4.0 visits/day
180 days (6 months)
~2.0 visits/day
365 days (1 year)
~1.0 visits/day
π’ What counts as a β#2 visitβ? Only visits that involve pooping (i.e., going number two) β urine-only visits donβt contribute to filling the composting bin and are not included in the estimate.
β οΈ Disclaimer: These estimates are approximations. The actual number of solid uses per bin may vary significantly depending on climate, temperature, ventilation, user habits, and the amount of dry bulking material (e.g., wood shavings or peat) added after each use.
(Based on approx. 1,000 uses involving a #2 β i.e., poop) – only the solids count!
Service Interval
#2 Visits per Day (involving pooping)
30 days (1 month)
~33 visits/day
60 days (2 months)
~17 visits/day
90 days (3 months)
~11 visits/day
180 days (6 months)
~5.6 visits/day
365 days (1 year)
~2.7 visits/day
π’ What counts as a β#2 visitβ? Only visits that involve defecation (pooping) β urine-only visits donβt fill up the composting bin and are not included in the 1,000-use estimate.
β οΈ Disclaimer: These estimates are based on typical, steady use. The actual number of solid uses a composting bin can handle may vary significantly depending on climate, temperature, humidity, ventilation, and how much dry bulking material (like wood shavings) is added after each use.
π§ Liquid waste (urine) estimate
Average person produces about:
0.4 gallons of urine per day (β1.5 liters β 1.6 quarts)
So for 100 people:
0.4 gallons Γ 100 = 40 gallons of urine per day
π½ Flush water use estimate
Average flush volume in the U.S. is about:
1.5 gallons per flush
Average person flushes ~5 times per day, so:
1.5 gallons Γ 5 = 7.5 gallons/person/day
So for 100 people:
7.5 gallons Γ 100 = 750 gallons of flush water per day