Toilet Water Conservation: TP vs. Bidet

We bought a new RV toilet out of necessity and a new bidet out of extravagance. It's weird to say, but these upgrades to our bathroom are quite exciting, mainly because with our old toilet leaking water into our holding tank, we were limited in our ability to boondock - something we had planned to do a lot of once we got solar. Now that we were back in business, it was time to enjoy a summer of boondocking: No water, no sewer, no electric, except for what we had on board. When going long periods of time without external resources, conservation is key.

We mentioned in the last blog post that an otherwise reputable source poo-pooed the idea of bidets for boondockers, but why? They assumed that the extra water use would mean faster depletion of fresh water and faster filling of the black tank. We assumed the opposite, which is why we bought the bidet in the first place. We had hopes that a stitch in time would save nine...or in this case, a spritz of water would save nine squares of toilet paper. So who was right, the self-proclaimed "geeks" who have been RVing for over 20 years, or us noobs? Granted, we noobs both have science backgrounds, and so there was only one thing to do: Create an experiment.

Question: How does using a bidet in an RV affect the amount of water used for flushing?

Hypothesis: The use of a bidet will decrease the overall amount of water flushed down the toilet.

Experiment: We installed a water meter between the fresh water supply and the toilet and bidet. The meter measured total gallons of water that flow through it. The full experiment lasted a total duration of two weeks.The first week consisted of regular use of the bidet with reusable toilet paper, using flushable toilet paper only when necessary. The second week consisted of regular use of flushable toilet paper, without the use of the bidet. At the end of each respective week, we observed the results calculated by the water meter, resetting the meter between each week.

Observations: The total gallons of water used during the first week (bidet use) was 4.2. The total gallons of water used during the second week (toilet paper use) was 9.7.

Conclusion: Prioritizing bidet use for seven days resulted in a 56.7% decrease in the net water usage in the RV toilet.

Discussion:

The purpose of this experiment was to quantify a belief that might be counter-intuitive to many, the RV Geeks included. At first thought, a bidet would mean using more water, simply because bidets use water. However, assuming the alternative is to wipe with toilet paper, RVers also need to consider how much water needs to be flushed in order for the toilet paper to dissolve. Because waste is held in a holding tank, disintegration is important. Using too thick or slow-dissolving toilet paper can cause build-up, so the best practice is to use toilet paper that is either specifically for RVs, or low-ply and septic safe. For this experiment, we used a single-ply, septic safe paper by Charmin. In our experience, this toilet paper's speed to break down was on par with other single-ply papers we have used. Our observations when dumping showed thorough dissolution while that paper was in the holding tank.

We are two adults, one male and one female, and have aimed to keep our toilet paper use low during our time living in an RV. When toilet paper is necessary, we tend to limit our use to one or two squares, except for the occasional times when more is needed. When flushing the toilet paper, we make sure that enough water is going down the chute along with the toilet paper. This typically means filling the toilet bowl with just enough water to submerge the toilet paper, before flushing it all down.

We decided to use reusable, non-flushable toilet paper cloths to dry ourselves off after spritzing with the bidet. Our bidet is a hand-held sprayer, which ran off our RV's water pump and had consistent spray pressure during the experiment. There is no way to adjust the volume of the spray. Similarly, the water used to flush also operated off the RV's water pump during the experiment and had consistent pressure.

While conducting the experiment, we made additional observations that further supported the use of a bidet for water conservation:

1. Because the handheld sprayer is maneuverable, we were able to target waste that otherwise had trouble flushing with just the water from the flush alone. This means that, instead of filling the bowl with even more water, we could spray the area directly, resulting in less overall water use in that specific circumstance.
2. The less toilet paper we used, the more thoroughly we were able to dump and flush our black tank, as more of the tank was taken up with liquids than would have been the case had more toilet paper been flushed.

Implications for boondocking:

Before installing the bidet, our typical maximum duration for camping without water/sewer was approximately 12 days. Due to the decrease in water flushed into our black tank, we now predict that we could extend our duration to around 20 days. This is accounting for the amount of bodily waste an adult couple produces on average, the capacity of our black tank (45 gallons), and our comfort level with how full we want our black tank to get. The extended black tank usage also opens the door for the gray tank (45 gallon) and fresh water tank (100 gallon) to potentially become our limiting factors in boondocking. Before switching to bidet use, the black tank was our limiter. If gray or fresh is the limiter in a future boondocking experience, we have options for extending our time through the portable dumping of our gray water, or the filling of our fresh water from a bladder. However, while this may be a valuable option for other RVers, we typically do not spend enough time camping in one location for this to become a factor.

The added use of a bidet might also result in saved gray water space, due to a need to shower less often, as the sprayer can target body parts that need more regular cleaning.

As we continue with our summer of boondocking, we will gladly take with us all that we learned from our scientific experiment, and we hope you found it informative too! Beyond the conservation aspect, the bidet has also proven useful for hygiene, comfort, and ease of cleaning the toilet. That's a lot of wins wrapped up in this little sprayer. So, if you're considering adding a bidet to your RV bathroom, it could be quite a delight! And as for water and black tank conservation? The proof is in the pooding!