I've been adding windows to my outdoor shed housing my well and water filter. The filter looks like the image below.

After adding these windows, I'm now noticing the inside of the filter is green, which I'm attributing to the water now being in sunlight.

We haven't noticed any taste/color/smell issues, but I am concerned about the color.

  • Do I need to bleach the well, or is cleaning the filter assembly sufficient?

4.5" filter in clear case

  • 1
    green stuff is algae, which feed on sunlight.They are also the reason why water tanks are usually kept in the dark. Commented Nov 29, 2016 at 11:46

2 Answers 2


You don't need to experiment with this system. What you have there is algae growth because you have opened up your well house to sunlight. This is a very common problem. Algae is every where, it is in the wind, all around you. Algae needs two things to grow, sunlight and water. You just supplied the sunlight. Eliminate the sunlight and you will not have any growth. I usually recommend to my clients that they make a boot out of insulation for there filter. Or you can simply replace your cartridge housing with a new one that is not clear. The clear ones are nice because you can see your filter and it indicates when to change. But, you already know that because of experience with when to change your filter out. So, Boot over the filter housing or change housings, problem solved.

  • Does color of the non-transparent housing matter? We have two options available Blue and White, my local filtration shop guy said to go for Blue and that White isn't as effective. To me both are opaque, so I don't see why there is difference since they both block light?
    – tunafish24
    Commented Jun 26, 2018 at 15:02

The best way to answer this question is to run an experiment. Here is how I would do that:

  1. Clean out the filter so that there is no green. (Filters need to be cleaned / changed from time to time anyway).

  2. Drape a doubled up black plastic garbage bag over the filter and adjacent piping. (I say double layer because most of these bags are surprisingly thin and a single layer can let some light through).

  3. Run the system through normal usage for as long of time as you have had the windows in place. (Try not to alter conditions too much such as adding or taking away windows or leaving the shed door open all the time).

  4. At the end of the testing period remove the covering again and see if the same green conditions appear.

If there is no green after the experiment and you find the water quality to be OK then you can simply decide to keep the cover over the filter.

It is not easy to determine too much about the filter that you pictured but it looks like a typical sediment filter designed to help keep sand and particulate from your well getting into your water pipes. The presence of the green in the filter is indicating that there is some organic content in your water source. You may want to consider adding an additional water purification filter at the point of use in the kitchen to clear out organics and other nasty stuff from water used for cooking and drinking.


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