Oh, Poo! A Review of BTS-33 Composting Toilet

Planning to buy a composting toilet but you’re concerned about the price? There are limited options when you are living off grid, and it’s hard to find an honest, unpaid compost toilet review. We bought an expensive composting toilet in the belief that it was the best option for our cabin since we had limited electricity and water.  Perhaps I can save you some time and money.A composting toilet seems like the very best answer to off grid living. Are they really? An honest - and graphic - review of our experiences with a waterless composting toilet in our off grid home.

Give me a moment while I remove my rubber gloves and put away the bleach, and then I will review the BTS-33 Composting Toilet by Biolet. When I was looking for a composting toilet for our off-grid cabin, I found many, many people who had this on their Pinterest wishlist but no one who had actually reviewed it after use. I should have been warned.

If you’re grossed out by the mention of feces, urine, maggots and other related stuff, you might want to stop reading. Have you read my Forgiveness series yet? Nothing gross there.

This post may contain affiliate links. When you support my sponsors, you support this site – at no extra cost to you, which is good, right? And there will be some gross talk about poop, too, AND pictures of maggots. That’s a important part of the disclaimer for this post.

The specific composting toilet that I talk about here seems to be no longer available. After the first time this post went viral, the company removed it – and all mention of it – from their site.

There are a number of different ways to collect and dispose of human feces (and sometimes urine). Most likely, you can think of more, but just off the top of my head, I have come up with a list of six and ranked them based on ease and enjoyment of use.


The portajohn has come a long way.

I just got off the phone with someone who services them, and I was quite surprised. Government regulations (at least here in Canada) mean that portajohns must meet a high level of cleanliness. No insects and no smell – they must be emptied every other week. I asked about chemicals, and they are only used for odour, not for treating the waste.

As for the waste itself, it is taken to a sewage treatment site, so it is essentially exactly the same as a flush toilet but without the water waste. That’s why I rank it as the first. Exactly like a flush toilet but it doesn’t use water. Awesome.

Okay, it’s outdoors, so maybe it should lose points for that.

Flush toilet

Honestly, who can complain about the modern flush toilet?

This is the gold standard of toilets when it comes to convenience and ease of use. The only real problem is that it requires a frightful amount of water to do something as basic as wash away our urine and feces.

So you're telling me that you poop in perfectly clean water?


Granted, no one ever likes cleaning the toilet and it is hard to reach behind it, but it certainly can be scrubbed clean.

I have never heard of insect problems with a flush toilet.

Any problems tend to be water leaking, drain backups, or the flush not working properly.

Standard composting toilet

By this I mean the composting toilets that use really amazing technology to perform the same job as the flush toilet – that is, they make our waste disappear – but they also turn our waste into usable compost.

Some of them have rotating drums like outdoor compost bins. Some divert urine so that it never mixes with feces. The ones I’ve used in the past had inner lids that kept the waste covered and hidden when no one is sitting there.

Really, they have come up with some really ingenious ways to quickly compost human waste.

The problem, though, is that the self-contained ones are designed for a single person or couple, and the large, family-sized ones require a tank in the basement.

These all use some kind of electricity since they are really not designed for an off-grid family. I found none of these fancy ones that, according to the manufacturers, were suitable for our family. All required a steady flow of electricity, or a basement tank, or they could not handle more than two people full time.


Really, it is just an outdoor bucket that is not easily emptied and cleaned.

Flies and odour are known issues, and no one really enjoys using them.

Granted, they don’t have to be disgusting, and a well-maintained outhouse is not a bad thing at all. However, they are pretty cold in the middle of winter, a night time trip means mosquitoes where you don’t want them and, really, how many people actually take good care of them? (I’ve been in a few. Blech!) And then there is the problem that the sewage isn’t being treated, composted or anything – it’s just being buried in a deep pit. That’s not the best option environmentally.

The best thing you can say about the outhouse is that it is outdoors, away from any dwelling, so it is kept away from where you eat and sleep.

Bucket system

As much as I disliked the bucket system, which we used from January 2015 until June 2015, the biggest problem is hauling the buckets out to the dump site. No one wants to do that, especially when the snow or rain is coming down hard.

However, a well-maintained bucket system actually has little smell and the buckets are easily cleaned with a bit of bleach, hot water and a toilet brush. We had people visiting our home when we were using the bucket system and no one noticed a strange smell.

Cathole in the ground and small shovel

This is the standard “poop in the woods” system and it works. The trick is to bury your waste.

However, I’d rather use an outhouse than go in the woods.

Honestly, I would have once considered this the least pleasant and least convenient option. About twenty years ago, I picked up a bacterial infection from going in the woods during the fall – peeing on a pile of decaying leaves. My doctor said that bacteria can travel both ways along the urine stream, so expect that anything you are urinating on is actually touching your genitals. That has made me very cautious about going in the woods or any other bacteria-laden place (and it meant that I emptied and cleaned our buckets often!)

I know – this is a LONG post. If you’re thinking about getting a composting toilet, you might want to read it through, though, since it will give you ideas on what to look for.

Biolet’s BTS-33 Composting Toilet

Perhaps I’m not feeling particularly generous, and I’ll admit that I am not very calm. To be fair, though, I spent an hour and seventeen minutes ranting to a sympathetic friend before I started writing this.

So I’m calmer than I was an hour and seventeen minutes ago.

Yes, the BTS-33 Waterless Toilet is at the very bottom of my list at this moment. By “waterless toilet”, they mean “composting toilet”, of course.

At this very moment, a cathole in the woods seems better. This is a long post, but I think you’ll find it’s worth the read.

As an important note – you can’t buy one. Biolet has removed the product from their website and scrubbed all references to it. I’m guessing I wasn’t the only unhappy customer.

Keep going!

Installing The Biolet BTS-33

We chose the Biolet BTS-33 composting toilet because the company representative assured me repeatedly that yes, it could accommodate our entire family, as long as we used an extra bin (and so we got an extra two, just to make sure, at a cost of $100 each), no, their composting toilet did not require electricity or water and yes, it would work.

I had multiple long conversations with them ahead of time to verify that the toilet was supposed to work in our off-grid cabin.

Well, for $1050, I expected it to do something pretty impressive. And I had a stupid moment and never once registered (until it showed up on my credit card) that $1050 is a lot more when converted from American to Canadian dollars. The composting toilet was getting pricey, so expectations were high. This would solve all of our off-grid toilet needs.

The following quotes were taken from the BTS-33 specific user manual, which they have since removed from their site.

Rated at 4 people full-time use and 6 people part-time use, the BTS 33’s capacity can be increased by adding optional composting bins. Each bin increases the capacity of the system by 2-3 people. Biolet Website

We installed it with the help of a very experienced retired contractor – my dad – to make sure it was in correctly. In fact, that’s part of the delay – we waited to install it until we had someone on hand who knew what he was doing.

As with all toilets sold by BioLet Toilet Systems the BTS 33 is easy to install by anyone with basic handyman knowledge in just a couple hours with common household tools.

Dad is better than “anyone” and he has a pretty impressive collection of tools. The website, by the way, mentions a few times that the composting toilet is easy to install. It was definitely installed correctly. However, nothing that goes through the wall or the roof is an easy install.

Just sayin.

When we installed Biolet’s BTS-33 Composting Toilet, I held off on posting a review because, quite honestly, I was underwhelmed.

The toilet went in, my father left, I looked at EJ and I said, “It’s a big, fancy bucket.”

“Well … there’s a vent pipe and drain tube. Bucket’s don’t have that. And it looks nice.”

Yup. He’s right. They don’t. Although they could, if you wanted to rig that up. And – it does. The composting toilet looks very pretty, especially since he put down new tile during installation, greatly improving our little bathroom.

However, I admit that I expected it to be more than, well, a pretty bucket bolted to the floor.

First impression – it’s a bucket I can’t easily empty (outhouse!), bolted to the bathroom floor, that is INSIDE my house.

We slipped the urine tube into our septic pipe so that it goes to the septic for now, while the feces would be turned into nice, healthy compost eventually. Right? Right?

Hurray for not burying all of our waste! After all, that’s why we were installing a composting toilet – a very, very expensive composting toilet, so that we could compost our waste and use it for fertilizing trees and such.

Hey, don’t stop now. It’s just getting good. Or gross. Let’s compromise on interesting.

My Questions and Concerns Regarding the Biolet Toilet

Still, I had nagging questions. Some of them are probably occurring to you, too. Am I right? Come on and keep reading for the rest of this crazy experience.

Like – is urine truly going to follow the suggested path instead of pooling at the bottom of the large, immovable base?
And – how exactly is an open bucket full of feces and urine supposed to not stink?
I have used composting toilets in the past and it wasn’t an open bucket – there was an inner lid, like in airplane toilets. Other composting toilets have drums that you rotate manually just like garden compost bins. This had nothing like that. No inner lid, no rotating drum, just an open bucket.

Its proven batch composting system combined with constant air circulation proves an excellent solution to almost any situation.

In case you’re wondering what “proven batch composting system” is, it means that you collect a bunch of stuff and THEN move it somewhere else to compost, after you’ve collected enough of it. So it sits in your bathroom until an appropriate amount as been gathered – which means several weeks.
And – shouldn’t there be something diverting the urine so it doesn’t mix with the feces? Because that … that isn’t going to smell good if the urine has to seep through feces and mulch to reach the drain pipe. I’ve raised animals – dried out poop doesn’t stink nearly as much as poop and pee mixed together. (And sitting for weeks – let’s not forget sitting for weeks.)
And – how often am I supposed to clean this, and exactly how am I supposed to do it? It’s not going to be as easy as lifting the lid and seat on a regular toilet.
And – won’t there be urine underneath the composting tray at all times? A standing puddle of urine in the bottom is not going to be a good thing.

Equipped with a convenient drain tube, the BTS 33 drains off any excess liquids to an auxiliary container, French drain or leach field. Since liquids are not a limiting factor, the BTS 33 will allow for applications where a larger capacity may be needed.

That means it will hold more poop because the pee is supposed to defy gravity and flow off outside.

Using The BTS-33

At any rate, we followed the directions and put down a 2” layer of mulch.
In for a penny, in for a pound. Okay, far more than a pound.
The price tag on this state-of-the-art composting toilet was $1,549, but on sale for $1049, plus $200 for the two extra bins. (It’s a longstanding sale, by the way, because it’s been listed that way for nearly two years …. just lower your price already.) That’s US dollars, by the way, so with the two extra bins it came out to something a bit over $1800 CDN.
“Did we check the price of this mulch, dear? Because this much at the bottom and then a half cup every time someone poops – we’re going to go through this stuff pretty quickly.”
So I checked. $39 USD for the 8 gallon bag bag, which “will last 2 people using a unit full-time for approximately 3 – 4 months”.
Oh, wait – there are five of us. I don’t like that math.
Now, the people using the toilet in our home right now are EJ, me, 7DS, 5DS and 2DD. Give the baby a year and she’ll be using it, too. (Edit: make that six months.)
The directions said to add 1/2 cup of that very expensive peat moss mixture after each fecal movement “or 1 quart per person per week”. With only 32 quarts in the bag, and about 2 quarts added at the beginning, it was looking like we’d be replacing that bag every 5-6 weeks. Oh, dear. This is looking like it will be costing us about $10 per week. Over $500 a year just to use the toilet?
According to them, using anything other than their special blend, which includes Canadian sphagnum peat moss (because “ALL PEAT MOSS IS NOT THE SAME”), will introduce insects and cause the toilet to work poorly.
That is important to note, by the way.
Anyway, what was with “or 1 quart per person per week”? Did they mean to let everything build up, open feces with nothing at all covering it, and only add the bulking agent once a week?
We were starting to see some real problems with this composting toilet.

You want to read about them, right? Don’t stop now.

Immediate Problems with the Composting Toilet

Swallow your bile, folks, we went with 1/2 cup after after fecal movement. And then sometimes a little more because … well, because it really was an open bucket and it quickly started to smell.

Let’s make it a little more vivid.
Some of the provincial parks have outhouses, and by the end of September, they desperately need to be cleaned or buried or whatever it is they do with the outhouses at the end of a busy season. The pile is sometimes so close it almost touches your bottom.
That’s the feeling I was getting with this toilet. Composting toilet, hm?
Bucket of rotting poop in my bathroom.
“I’m sitting a foot above everyone’s poop from yesterday. And it still looks and smells like poop.” The little sprinkle of peat moss does little to disguise the fact that there’s a pile of smelly poop just under your bottom.
After the second day, the composting toilet began to stink.
No, I mean really, really stink.
The bathroom window was opened wide because the smell was unbearable otherwise. We tried scented candles, but I forgot that chemical scents and I do not get along well.
No one can accuse me of being squeamish. I managed with a bucket system for six months. Honestly – the buckets, with a lid, changed daily (and sometimes more often) did not actually smell bad. People could come into my house and they wouldn’t know unless we told them.
The manual warns not to have the window open because that will cause it to smell. (The stink came first!) It seems that almost anything can throw off the way that stink vent works, including an open bathroom window. Let’s really let this register – if you install a BTS-33 composting toilet, you are never supposed to open the bathroom window or have a fan or exhaust in the bathroom.
Better hope you don’t have a moisture issue in that tiny room filled with …. hot, steamy water.
“Perhaps it needs time to settle into its compostiness?” I asked EJ. “…. Does that mean we put up with a couple of weeks of stench every time we change the bucket thing? This thing smells bad.”
Finally, after ten days of putting up with the reek of this disgusting pseudo-toilet, I had had enough.

In a full-time residential setting, the compost bin should be emptied when the bin is about 3/4 the way full of once every six months.

Ten days. That’s close enough to six months, right? This has to get out of my house.

When a compost bin fills, just remove the bin and move it outside for further composting and place the next bin inside the unit.

Anytime someone tells you to “just” do something, run. It is never going to be a simple task. If you have a strong stomach, keep reading. This is when the **it gets real.

Changing The Bin


In order to change the bin or clean inside, the entire top of the composting toilet must be removed, and it is pretty large and awkward.

I removed it and placed it in the bathtub (yes, it’s that large), put the lid on the composting bin without really looking at anything, and carried it through the kitchen and outside.

Use a sponge or sponge style toilet brush and liquid soap or some other mild detergent when cleaning your BTS 33.

The composting bin, it should be noted, leaked a delightful mixture of urine and liquid feces. Gee, how did I see that coming?

*Insert late night bathroom and kitchen floor washing*

Back in the bathroom, I notice that there are little … lines? Strings? all over the inside of the composting toilet’s base. I look closer and they wiggle.

Maggots. Huge gray maggots.

Oh. My. Goodness.

Blowfly maggots are covering every interior surface of the toilet.

I have pictures  …. this is where you can be happy it’s pictures and you’re not in the room.

Composting toilet after just TEN days

The bottom of the base is covered with a disgusting mixture of urine and liquid feces, with maggots swimming in it.

Rubber gloves.


Hot water.

I know, I know, I know – with the urine dripping down to the septic, I just hit my septic tank with a few cups of bleach.

I know.

It’s very bad.

But I don’t really care. Hundreds of blowfly maggots in my bathroom, in my toilet!

Composting toilet and maggots after just ten days

It is important to note that we had been using this toilet for ten days. That’s all.

The base of this composting toilet is IMPOSSIBLE to clean completely. It’s like cleaning the water out of a plugged bathtub (except a plugged bathtub full of dead maggots).

Hurray, I’m learning new, earth-friendly ways to kill maggots. That should prove useful … never.

Why isn’t the drain pipe just at the bottom like any other drain pipe ever? It is at the back with a stupid wall around it to prevent everything from going down. It took me hours to get those dead maggots down the drain, and then I had to get a ladle to scoop out the last of it.

Now at least I understand where the flies I couldn’t get rid of were coming from.

Maggots in my toilet.

According to the manual, if I find insects (insects sound so nice, why don’t we call them blowfly maggots and larvae?) inside the composting toilet, I am to hang a “no pest strip” which lists Dichlorvos as the ONLY active ingredient in there. And since “only” really is written in capital letters, they seem pretty serious about it.

Well, um, that doesn’t sound like something I want on my property.

Dichlorvos is an insecticide used on crops, animals, and in pest-strips. Acute (short-term) and chronic (long-term) exposures of humans to dichlorvos results in the inhibition of an enzyme, acetylcholinesterase, with neurotoxic effects including perspiration, vomiting, diarrhea, drowsiness, fatigue, headache, and at high concentrations, convulsions, and coma. No information is available on the reproductive, developmental, or carcinogenic effects of dichlorvos on humans. A study by the National Toxicology Program (NTP) reported an increased incidence of tumors of the pancreas, mammary glands, and forestomach in animals. EPA has classified dichlorvos as a Group B2, probable human carcinogen.

What do you think? I feel bad enough when I use bleach. (And I mean that in two ways – I am cautious and concerned about it, but I also find it physically difficult to be around things like bleach).

So what do I recommend – after living with a bucket system, a toilet we had to flush with a pail and the very expensive BTS-33 Waterless Composting Toilet?

Keep reading to hear my final thoughts on this.


Right now, I would not recommend this composting toilet to anyone, not even if it were free.

I’m disgusted and discouraged. For less than $100, we could have built a very nice humanure toilet using a couple of easily-changed buckets, with separate buckets for urine and feces, mulched with inexpensive and abundant wood shavings. That would be my recommendation if you can’t run a standard electric composting toilet.

A humanure toilet won’t look as pretty, but:
a) you can change it daily,
b) you can use any bulking agent you like and/or have available
c) it won’t cost you *thousands* of dollars
d) a lid on the bucket will keep flies out
e) easy to separate urine and feces
f) easy to clean

Follow Up

Sleep finally overwhelmed my disgust at 3am, but at least the bathroom was clean, with the offending bin outside.

The next day was Inspect The Toilet day.

As far as we can tell, everything is installed correctly.

We added the 2” of bulking agent again, with a new bin in the very clean base, hung more fly strips in the bathroom, and are diverting urine directly to the septic pipe. I still feel that mixing urine and feces is a bad idea and that the urine is what attracts the flies. EJ put a screen over the stink vent as that was the only reasonable way the flies got in.

After two days, I checked – no maggots yet.

On day four, no maggots, but I woke with the stench of sewage through my house again. I opened the toilet top to check and gagged on the smell.

A phone call to the company was painful.

We must have installed it incorrectly. Except that we didn’t. This is not rocket science and their own website says that “anyone” can install it with a few common tools.

He continually asked me if we had use “90 degree elbows” to vent it outdoors.

I said, “We used ONLY what came in the box.” Those were 45 degree elbows. Well, we still must have installed it wrong. Stupid pipe goes out the back of the toilet, through the wall and up. As I said, not rocket science.

Right now, it seems that we might need more pipes for the stink pipe, to make it higher than the highest point of our house (which would be the chimney). And we need to buy the pipes, of course.

Or perhaps we need an electric fan attached to our non-electric toilet. Which we would need to buy, along with a solar panel and battery to run it.

Or maybe, because it’s so windy here in Nova Scotia, we need a special wind directional cap, which they sell for only $99 USD.

“It’s like being a scientist!” he says. “Trial and error until you figure it out.”

“Great,” I replied. “And in the meantime, your disgusting toilet is costing me a lot of money and stinking up my house.”

“Oh, it’s a good toilet. We have them installed all over the world.”

People all over the world have low standards.

As I said, they’ve removed this toilet, and all mention of it, from their website.

The one good thing about the conversation is that he admitted that the only really necessary parts of the bulking agent are peat moss and wood shavings. The rest “makes it a superior product”.

Today I removed the bin again. It was full and heavy – no, nothing dehydrates, it just piles up. EDIT: after about a month outdoors, the contents shrink by about half.

It leaked, too, just like last time, so I once again cleaned liquid feces off my floor. Since there are holes in the bottom of the bin, when you carry them across your kitchen floor and out the door, liquid feces drips everywhere.

And, wouldn’t you know, there were maggots. Not as many as last time, but still plenty.

This time I didn’t panic – boiling water kills them, too. They don’t like straight vinegar much, either.

Hurray, I’m learning earth-friendly ways to kill maggots.

We now have two full bins outside which are not going to biodegrade anytime soon, one in the composting toilet and only one left. At this rate, we’ll be switching out for the fourth one in less than two weeks.

In the meantime, we received a bill today from Fedex – $262 CAD for customs and duties. And we’re completely out of their proprietary bulking agent.

Where’s the shovel? I’m heading to the woods.

EDIT – In the spring, BEARS are attracted to this pile of non-composting poop and toilet paper. Be warned. It’s kind of disgusting and dangerous. So I never discovered how long it takes to decompose.

EDIT – After we moved out of the cabin and left the toilet bin alone for SIX MONTHS, it still was sitting there looking like a pile of poop and toilet paper. Six months after that, in the late summer, it was a pile of poop and paper with abundant insect activity.

To wrap up – I am extremely unimpressed with the BTS-33 Composting Toilet.

The proprietary bulking agent is expensive and unsustainable.

The design of the base means that a urine overflow causes a disgusting mess that attracts flies and is difficult to clean. Any toilet that relies on dichlorvos to prevent a fly infestation is not eco-friendly.

And one final, nitpicky issue.

They designed the toilet to look like a regular toilet. The problem, though, is that the bumps and grooves and indentations on a regular toilet all have a purpose.

With the BTS-33, the only purpose I can see is making the composting toilet harder to clean. The back is too low to lean back against, so why is it there except to collect dirt? There are ridges around the outside of the base that simply …. collect dirt.

The people who design these things should have to spend a month cleaning them.

P.S. I really hate this composting toilet. $1830 CAD + $262 customs/duties + $32 for a 6′ length of pipe to extend the stink chimney + either an electric fan or a turbine vent or a wind directional vent. At least wood shavings are free because I’m not paying $39 USD for their “proprietary blend”. Oddly enough, it stinks less with plain wood shavings!

The composting toilet now works just fine – as long as no one pees in it!

A composting toilet seems like the very best answer to off grid living. Are they really? An honest - and graphic - review of our experiences with a waterless composting toilet in our off grid home.

A composting toilet seems like the very best answer to off grid living. Are they really? An honest review of our experiences with a composting toilet