What our bidet taught us about our RV's black tank

One year ago, we were looking for ways to boost our morale in Wyoming. We ended up at Longhorn Ranch, an RV park that turned out to be a welcome regrouping stop, and a stay that brought us a lot of dear memories. One of those memories was the purchasing of our bidet. You might not think that adding a bidet to our RV would end up a core memory, but we tried a lot of bidets over the course of several weeks, and on July 21, we finally found "the one."

Why the intensive quest? We thought that having a bidet would help us conserve tank space while boondocking our way through Wyoming. We were right. But something fascinating happened during that little science experiment, and might we say, we blew the lid off a whole new mess of problems, a mess that we've been trying to clean up ever since. Now, we are happy to finally conclude our story about our black tank woes, and we see no better opportunity than our 1-year bidet anniversary – our Bidet-day!

It all started about 2 months into our full-time RV life. We had made our way from Massachusetts down to Florida, escaping winter and finding a very summerlike spring. March in Florida is usually ideal weather, but we suffered through temperatures well in the 90s. The heat was unbearable, but to make matters worse, we began to notice a rather unpleasant odor coming from our bathroom. We spent a lot of time at Koreshan State Park that year, and it was the longest we had been at a campsite without sewer hookups. We were learning how to conserve, and all in all, things were going well, except for that odor. We were newbies, so we chalked it up to the heat expanding the gasses and causing some to leak out.

We spent a very long time monitoring this issue, but finding no evidence of anything wrong except for the smell. It continued to be worse on hotter days, and the rest of the time, we didn't really notice anything.

We should probably paint a more detailed picture of how we traveled in 2022, because that plays a huge role in our story. When we first hit the road, we were having water pump issues, which made us unable to stay in campgrounds without water hookups. We were also much more conservative with where we stayed because we were still learning the ins and outs of our rig: How to maneuver it, how to conserve our tanks, and all the usual maintenance that needs to be done as we gather up our travel miles. Because of this, we rarely stayed places without full hookups. Koreshan was only our 2nd water and electric only site, and certainly our longest stay at a water and electric site up until that point. After that, we had a few sites without sewer, but most were not in as hot temperatures and were shorter durations. When we did stay somewhere longer without sewer hookups, the bathhouse became our friend, as did our Camco tote for gray water. We even had Honey Wagon service at one of our water and electric sites during the summer, despite only staying for a week!

This more conservative style of travel worked for us in our first year, but come 2023, we were headed out west, where we would have ample opportunities for boondocking. We were good to go: Our water pump was fixed, we were familiar with our rig, and we even got so confident with our tank conservation that we got rid of our Camco tote! But, just as soon as we had forgotten about the gassy days of Koreshan, they came wafting back.

Sites without sewer hookups in 2022: 9
Sites without sewer hookups in 2023: 27

If those stats are any indication of how much we changed our travels, let them also be an indication of why our black tank issue was brought to light in 2023, not 2022. We also hit some hot hot heat in a lot of our locations. During our 2nd stint in Vegas Bay, temperatures were reaching triple digits and we were so deep in RV issues, we had to extend our stay multiple days. This was when the black tank issue really smeared itself all over our travels, but once again, we had an excuse. Of the many RV issues going on at that time, one was with our toilet, and in order to fix the issue, we had to run a lot of water down into the black tank. Poor Anthony also had to unbolt the toilet from the floor multiple times, including when the black tank was full. He saw things that no man should ever see.

This was a turning point for us because it was the first time we ever actually filled our black tank. As frustrating as this whole stay was, we gained valuable insights into what our tank sounds like at certain points of fullness, and also what it smells like at certain points of fullness. This was when we started getting suspicious. Everything we had researched mentioned hearing a "gurgling" or "burping" sound shortly before the black tank becomes full, and that's the indication to dump – a far better indication than checking the levels on our panel, because RVers quickly learn that those end up not working after basically any waste gets in the black tank. There are other techy devices you can add, but most people just use their ears and it works fine. But were our ears playing tricks on us?

We would hear the "gurgle gurgle burp burp" long before we expected to be full. This became a regular occurrence as we traveled our way through the West.

Something else that became new to us in 2023 was how often we would drive with a partially full or full black tank. We tended to stay at a few sites with no sewer hookups and then squeeze in a full hookup regrouping stop. As such, we wouldn't dump on our way out and would just wait until we got to our full hookup spot. Those days were some of the smelliest we've ever experienced. We remember one drive in particular in Wyoming, when we were heading over the Cloud Peak Skyway Scenic Byway, on the southern border of Bighorn National Forest. We stopped at a pullout on top of one of the hills to check our brakes and tires before making the descent. As we did our walkaround, even just passing by our closed front door, we could smell an awful black tank odor. This could not just be gasses escaping through the toilet. Actually, we knew this for a fact because just the previous month, we replaced our toilet with a brand new one, and all the seals looked good and secure.

We had never RVed before buying this trailer for full-time travel, and we honestly didn't know how much black tank smell should infiltrate our RV, and therefore, our lives. We expected a bit of smell if the tank was nearly full, and we even thought some smell during drive days was normal, but the more we traveled, the more we thought "no way." If people were smelling this on drive days, they'd be talking about it! Even on days our black tank was only a little full, we'd make pit stops and have trouble even staying in our rig until we could open all the windows and air it out. Forget trying to eat lunch!

This was when we started scouring the RV forums. No complaints about black tank smell on drive days, at least not how we were experiencing. In fact, we saw a post by one guy who said that he actually prefers to drive with a full black tank because it loosens up the waste and makes dumping easier. When we heard that, we knew what we were dealing with wasn't even close to normal. If we tried to swish swish our ish on drive days, we would be inviting an odor most foul. We would never subject ourselves to that on purpose!

As you can see, these black tank issues permeated our entire journey through Wyoming, but at this point, we weren't exactly sure how many issues we were dealing with. On one hand, we had the smell. On the other hand, we had the odd timing of our audible indicator of black tank fullness.

Ever since Vegas Bay, we suspected something was wrong with our black tank, but after we installed our bidet, we ended up getting definitive proof.

The plan for our conservation experiment was to go one week using the toilet as normal, followed by another week using the bidet as much as possible. We used a water gauge to track how much water was going down the toilet. This was, of course, to see if we flushed more water using toilet paper or the bidet sprayer. Little did we know that we were running another test at the same time.

We have a 45 gallon black tank, and in the first week of our test (using toilet paper), the water gauge showed that we used almost 10 gallons of water. Factoring in the typical amount of waste that two adult humans produce, we can estimate that we added somewhere between 5 and 12 gallons of waste, meaning that our tank should have been under half full by the end of the week. In the second week (using the bidet), we used just over 4 gallons of water, meaning that at the end of the week, the tank should have been between 1/4 and 1/3 full. This coincided with what we had heard from other RVers, that with normal use of their toilet and a 45gal black tank, they could go at least 2 weeks without dumping. We always assumed this would be the case for us as well, and once we discovered how much water we conserved using our bidet, we saw even more possibilities for long-term boondocking. We could go 3 weeks without needing to dump!

Only, our toilet was telling us something different than our calculations. During week 1, we began hearing the "gurgle gurgle burp burp" around day 6. During week 2, we didn't dump right after we finished our test, and we started hearing it around day 9. If our tanks should have been nowhere near full in either situation, what was going on?

We flushed out a lot of theories. Was our black tank built wrong? Was it tilted? Was the pipe leading into the black tank too long or somehow positioned wrong?

We kept asking ourselves these questions while we collected information and data.

The next time we got on full hookups, Anthony tested things once again. He used the gauge to add specific amounts of water into the black tank, in increments. Here was the data he collected:

1. The toilet started gurgling at between 20-25gal water in an otherwise empty and thoroughly flushed tank.
2. Anthony was able to put at least 43gal of fresh water into the tank, which confirms that we don't have any buildup. We both knew a poo pyramid would have been far too simple an answer!

Anthony also got advice in the ATC Toyhauler Owners group.

After weeding through the unhelpful answers from people who didn't actually read or understand the question, we found support for one of our theories.

Then, an answer that connected it all together for us:

Ah yes, the vent. The silent killer of this whole debacle. In addition to the pipe that runs from black tank to toilet, there is another pipe that runs from the black tank to the roof. This pipe should never be submerged in black tank contents, because it's supposed to let sewer gasses escape out the roof. Basically, when waste goes into the tank, it gets held in water, and the gasses release through this vent. If the vent pipe is too long, it can get submerged in the waste, and the gasses get trapped. This not only causes odor when the gasses escape into the RV (either when it's flushed or if the toilet isn't secure to the floor), but it also can create a pressure change when you add additional volume to the tank. Water (and waste) get pushed into the vent pipe, and when the contents try to equalize, the air at the top of the vent pipe pushes the waste back down and toward the toilet pipe. This can cause excessive gas and premature burping.

We had given the vent pipe some thought before this. On a few of our odorous drive days, we noticed that the smell didn't seem to be coming from the toilet as much as the wall where the vent pipe leads out to the roof. This could also be the reason we smelled something outside our trailer that day in Bighorn National Forest. We hadn't put all the pieces together yet, but we did also feel that our vent pipe needed rinsing a lot more than we assumed was normal, but we didn't know for sure. After all, this was our first RV! (We now know that some people don't need to do it ever). With these observations, we knew that the vent pipe could very well be one of the causes of our problems.

We ventured into fall feeling good about our data collection. We'd likely be looking at either too long a toilet pipe, too long a vent pipe, or both. We had a service appointment at Complete Trailers outside of Denver in September, and on our list was for them to check our toilet pipe and see if they could give us anymore information. They unbolted our toilet and checked the pipe, but couldn't see anything wrong with it. They did, however, replace some of the bolts securing the toilet to the floor because some seemed loose. With all the bolting and unbolting we needed to do with both our toilets those past few months, we weren't surprised. Complete was hopeful that maybe securing the toilet tighter would solve our problem, but we weren't that lucky. We would need to wait to have ATC take a look.

It would be a long wait. We were heading back home to Massachusetts for the end of the year, and then setting back out for our 3rd season of travel, which wouldn't be taking us to Indiana until the spring. That would mean 8 months of dealing with our black tank woes.

We thought we were done collecting data, but more got dumped on us when we accidentally filled our black tank while moochdocking at Nicole's parent's house for the holidays. We had a cracked seal around our vent pipe, which allowed rainwater to seep in, filling our black tank quicker than we expected. The whole situation was a mess, but something we did notice was a change in our audible indicators of black tank fullness. We got our "gurgle gurgle burp burp" when we expected, aka far earlier than at 90% full. Then, a few days before our tank filled, we stopped hearing it. We wondered what was happening, hypothesizing that perhaps our slightly unlevel positioning made the black tank contents find some extra room. How wrong we were!

Looking back, now we can assume that the tank was so full, no pressure changes could happen because the waste had nowhere to go.

Our running theory going into this year was that the vent pipe was the culprit all along. ATC was ready to replace it, and we all kept our fingers crossed that this was the solution we had been patiently waiting for since the gasses tickled our nose hairs in Koreshan, a long 25 months before.

We have been alluding to this black tank issue for many months, saying that we hoped we would be writing a dedicated blog post once we brought the trailer to ATC and got our long-awaited conclusion. We are happy to report that this is indeed that post! ATC replaced the vent pipe, and since then, we have been living a delightfully smell-free travel journey. The longest we have gone between dumps has been 10 nights/11 days, and we have heard and smelled nothing. We have also taken several drive days with a partially-filled black tank, and we can enter our rig at a pit stop, cook food, and eat it without feeling like we're going to vomit! The funny thing is, we had been living with the stench for so long, but now that it's gone, it's just a distant memory. We don't even pay any mind to what our RV used to smell like on those travel days.

This was definitely a newbie RVer issue, having no comparison points when we first got this rig. We heard so many stories about "dumping" and "black tanks" and "smells" that it was hard to know what was hyperbole. We wish we didn't need to learn this much about the inner workings of our black tank, but now that we have, we will be much better prepared for any other issues that might arise either with this RV, or any RV of our future. One thing is for sure, though: On our list of RV problems we've had over the years, this one really ranks high.