The best toilet paper for a septic tank isn't necessarily determined by ply because not all two-ply papers will behave alike. Fibre alone does not sufficiently answer the questions. What matters is whether the finished tissue has been designed to lose strength and disintegrate readily in water and that is influenced by various factors, which we cover here.

What makes toilet paper septic safe?

Regardless of whether toilet paper is made from Pine or bamboo, the fundamental structural element in all plant cell walls is cellulose. Cellulose is a complex carbohydrate that forms part of cell walls providing strength and structure. So when toilet paper is flushed, the immediate issue isn't whether the cellulose will eventually biodegrade. First, the sheet needs to wet out, lose strength and break apart into smaller pieces and fibres. 

This research testing 51 commercial tissue products found that most bathroom tissues reached 100% disintegration within 30 seconds under the ISO 12625-17 test. Researchers identified properties including wet strength (additives that allow the paper to resist tearing once wet), loss of strength after wetting, surface characteristics and softness as factors all affecting disintegration. 

Does toilet paper dissolve?

Not exactly. Toilet paper is often described as “dissolving”, but disintegrating is a more accurate description of what happens immediately after flushing. Water weakens the bonds holding the tissue structure together, allowing the sheet to break apart and disperse into smaller pieces and fibres — this is disintegration. Those cellulose fibres can subsequently biodegrade under appropriate environmental conditions. Disintegration and biodegradation are related, but they aren't the same process.

Why does some toilet paper break apart faster than others?

Toilet paper has two tasks which are somewhat contradictory. The tissue needs enough strength to remain intact while you're using it, but ideally should lose that strength quickly once it's flushed.

Manufacturers can achieve this balance in various ways. Research into toilet tissue production has found that greater fibre bonding can reduce disintegration, while controlled refining and the use of softeners as de-bonding agents can change the strength, softness and disintegration time of the finished tissue. In one experimental study, researchers were able to produce tissue with an eight-second disintegration time by adjusting these variables.

Fibres in toilet paper are bonded primarily through natural hydrogen bonding and physical mechanical entanglement as water is drained and dried from the cellulose pulp. In other words, how strongly the fibres are bonded together can matter more than simply whether those fibres are bamboo, recycled paper or wood. The best toilet paper for a septic tank is one designed to break apart readily in water. 

Does ply matter?

A 1-ply toilet paper will generally contain less material per use than a thicker multi-ply paper, but ply alone doesn't determine how quickly toilet paper disintegrates. Strength, fibre bonding, embossing and other aspects of tissue construction also affect how the finished sheet behaves in water.

In research testing commercial bathroom tissues ranging from 2-ply to 4-ply, most reached 100% disintegration within 30 seconds. This is also why two different brands of 2-ply toilet paper won't necessarily behave identically once flushed.

Is recycled toilet paper better for septic tanks?

Recycled toilet paper is commonly recommended for septic systems, sometimes on the basis that its shorter recycled fibres biodegrade more quickly. Research doesn't provide a good basis for making that generalisation. One study comparing virgin and recycled-fibre toilet papers under anaerobic digestion found their ultimate biodegradability was within the same range. The researchers noted that differences could be associated with factors including physical fibre characteristics, pulping, lignin remaining on fibres and additives. 

So again, fibre source alone isn't enough to predict how a particular toilet paper will behave.

What shouldn't you flush into a septic system?

Going back to the evaluation of disintegration in water of tissue papers study, the researchers found that facial tissue, paper towel, travel tissues all scored poorly. This makes sense when you consider what these products are designed to do. A facial tissue needs to remain intact when you blow your nose, while a paper towel needs to stay strong enough when wet to clean up a spill. Toilet paper is engineered to do almost the opposite: hold together during use, then lose strength and break apart readily once flushed.

For this reason, facial tissues and paper towels shouldn't be used as substitutes for toilet paper and flushed into a septic system. These tissues will water log, congest pipes and potentially fill up septic tanks much quicker causing expensive sewage backups or overflows in public wastewater networks.

Is bamboo toilet paper safe for septic tanks?

Yes, bamboo toilet paper can be safe for septic tanks. But bamboo alone isn't what makes it septic-safe. Bamboo provides the cellulose fibre used to make the tissue. How readily the finished paper breaks apart depends on how those fibres have subsequently been processed and bonded into a sheet. Rather than assuming a toilet paper is septic-safe because it is bamboo, recycled or a particular ply, look for information from the manufacturer about whether the finished product is suitable for septic systems and, where available, how its disintegration has been tested.

If you have a septic system, be cautious about assuming that toilet paper marketed as “ultra-soft”, “ultra-strong”, “premium” or “quilted” will break apart readily in water. This research has found that some premium toilet papers disintegrate more slowly than average toilet papers, although this will not be universal for all products with similar qualities.

So, what toilet paper is best for septic tanks?

The best toilet paper for a septic tank is one designed to lose strength and disintegrate readily after flushing. Bamboo and recycled fibres can both be used to make septic-safe toilet paper, but neither fibre guarantees it. 

Rather than relying on claims about fibre length, biodegradability or ply alone, look for information about the finished product and whether the manufacturer states that it is suitable for septic systems. 

In EcoRoll's own dispersibility test, our 2-ply and 3-ply bamboo toilet paper visibly broke apart under agitation in water within approximately 15 seconds. This was an in-house test rather than testing to a recognised standard.