Yesterday, we filled in all but the last filtration layers of the slow sand filter prototype we started recently.

Before we could fill it up, we needed to make the hole for the pipe water tight. It turned out not to need any silicone since the cement seal seemed water tight enough.

The process we used was to first mark a line on the inside of the urn for each layer height. Then we filled up about 20cm of water before dropping in a 10cm layer of washed gravel up to the first line. This was followed by layers of small pebbles, coarse sand, and fine sand. Each time, we used a hose to fill in the water up above the height of the next layer.

Next we will put in the rice husk ash. After that, we just need to cut the outlet pipe to the right height and it will be ready to test.