Use medium to coarse silica quartz sand with particle sizes between 0.4 mm and 1.2 mm. It should be chemically inert (not react with water or alter the system’s pH) and free of silt, clay, and organic matter. Avoid beach sand. A sedimentation test can help determine if the sand is suitable. It’s often sold as ‘builders sand’, or ‘concrete sand’, and in many places can be found pre-bagged in retail outlets.
Sand with fines, silt or clay will negatively affect drainage and aeration and may lead to clogging.
The most important thing is that the sand drains well. An ideal mix will have;
- 40% of the sand particles to be between the size of a pinhead or a small ant (that’s between 1 and 2 mm).
- 40% should be a bit smaller, about the size of a grain of table salt (0.5 to 1 mm).
- 20% should be even smaller, about the size of fine sugar (0.25 to 0.5 mm).
It’s okay to have a few particles larger than 2 mm, avoid having particles smaller than 0.25 mm. The ideal sand should have a consistency similar to table salt or granulated sugar, with no powdery fraction or particles that could cause clogging.
Crystalline quartz sand, also known as silica sand, is generally the best choice for iAVs. It is chemically stable, pH-neutral, and has excellent drainage properties.