One of the things I definitely needed as part of my big plan was a way to prefilter raw water. In treatment plants, water is pumped into settling tanks with aeration and flocculant to get all the particles out, then it goes to finer filtration and chlorination. In my scheme, I didn’t have anything ahead of my Berkey ceramic filter which would tend to limit the throughput for drinking water (clogs from sediment). It also didn’t allow for a source of filtered but non-potable water for washing.

The usual solution for filtering is a “slow sand” filter, it’s a large column of sand with a diffuser on top and a drain at the bottom. It’s big and heavy, they need to be at least 55 gallons to allow the bacteria to trap and digest any harmful impurities. It is also slow, just a trickle, and also needs to be run for a while to develop the native biofilm. Rather than do all this, I made a smaller version that just traps particles. The goal was to pour asswater in the top, and get clean non-turbid stuff out for either bleach treatment (washing) or for the Berkey and Pur filters for drinking and cooking.  Here’s a few pics:

Empty plastic bucket with the copper manifold and outlet

A couple of notes. I used 40 grit paper on the sides, this is to trap the sand grains and not let any water past the sides. This is a big deal with the slow filters, so I went ahead and treated it. The pipe manifold is copper, there are a bunch of 1/8″ holes underneath that let the water out. I used copper for the antimicrobial properties and easy assembly, but plastic would be fine.  I added a 3″ layer of pea gravel on top of this, to prevent the sand from migrating out the manifold.

Here it is with the pea gravel and play sand fill. I left about 1 1/2 gallons of headspace to give it some working volume, but still have a filtering action.

In action. You can see the fine sand it spit out on the first fill, that went away quickly and the rest was crystal clear. Playsand is very fine, almost dust like, and seems to do a good job filtering sediment. I pulled a bucket of pond water, let it sit a few days, then poured it in. Out came nice clear water, albeit with a faint musty lake smell.  This will be run through my other filters soon, and I’ll see how it is. I think using an aquarium bubbler on the filtered water might eliminate the odor, will probably try that as an experiment.

So far, so good though.