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How To Care For Your Rainwater Harvesting

How to Treat your Drinking Water

This will detail a step-by-step approach to maintaining your Drinking Water.

  1. How does Rain Water Collection Work?
  2. How to Set up a New System?
  3. How to Monitor Water Levels?
  4. Is the Pump not Starting?
  5. When to Replace Filters and Lamp?
  6. How to Replace Filters and Lamp?
  7. How often Should the Tanks be Cleaned?

  1. How does Rain Water Collection Work?

    The rain water progresses from
    1. Roof
    2. Gutters
    3. Downpipes
    4. Pipes underground
    5. Water Tanks
    6. Pump
    7. Treatment
    8. House
  2. How to Set up a New System?

    1. Roof : Most roof types are fine for water collection. However, there is a huge question mark over asphalt roofs. These were designed in a different climate to Australia and New Zealand. They probably should not be used in this part of the world. The problems -
      1. Over time, the stones will wash away straight into your water tank. This happens because of the weathering action of the rain and because the bitumen becomes harder.
      2. Just like the roads, a long dry spell makes the oils in the bitumen rise to the surface. Heavy rain soon after washes these oils into your water. When this happens, our water is distinctly yellow.

      Surely they have been tested. Yeah right, the AS/NZS 4020:2005 requires cold water application up to < 40°C at the 'total immersion' exposure of ≈21,429 mm²/L test water at (20±2)°C. They don't have even flowing water and the water temperature is only 18 to 20! There are no issues with the supplier, manufacturer or tester. It's the test that was written by a moron. An example of a test certificate can be downloaded here.[1]

    2. Gutters : The first point of interception of rubbish is the gutters. Traditionally, a hedgehog (bristles) is used.
      1. Pros : Nesting material and leaves are trapped in the gutter.
      2. Cons : The trapped material stays here allowing water to pool in front of it and allowing grass to grow in the gutter. The gutter really needs cleaning several times a year.

    3. Downpipes : Rubbish may also be intercepted at the top of the downpipes. There are several gadgets (leaf diverters) on the market, that allow rubbish to slide away over a mesh.
      1. Pros : It is almost self-cleaning and requires only a periodic hosing.
      2. Cons : It makes the downpipes and the ground underneath a little messy. The mesh on most of these allows way too much rainwater to slide off as well. I have used an early Marley model. After I reported the issues, they co-operated and came to the party and altered the mesh size to a good compromise.

    4. Pipes underground : You don't want the pipes under the ground to get clogged up. So it makes sense to have some of the previous two solutions, especially on areas where there are more leaves and bird activity. We do not have any large trees nearby and only two sections of the guttering have bird activity, so we just have two hedgehogs.

    5. Water Tanks : come in various sizes and materials. I prefer concrete as it allows the water to breathe. I am not aware of any negative impacts on other types. The final place to intercept the rubbish is here. There are baskets (tank debris baskets) on the market (we have one on each of two tanks).
      1. Pros : They are at ground level and easy to clean. The baskets are removable and can just be emptied and hosed clean.
      2. Cons : The material does travel through the pipe and there is a danger that the rubbish could accumulate in them.

    6. Tank Connections : There are three schemes -
      1. In Series : In this scheme, all of the pipes from the house connect to the first tank. This overflows to the next tank which overflows to the next one.
        1. Pros : The final tank has really good quality of water, sometime referred to as gold.
        2. Cons : If it is a large roof area, the volume of water may overwhelm a single point of entry into the tank. We have had water overflowing the gutter in severe rain because of this.
      2. Semi Series : In this scheme, the pipes are divided into two to feed two tanks simultaneously. Both of these overflow to the third tank.
        1. Pros : The final tank has a reasonable quality of water.
        2. Cons : None, we use this scheme. We draw water from the last one. When this gets empty, we switch to the other two.
      3. Self Levelling : In this scheme regardless, of how the inlet pipes are connected, the outlets are connected together.
        1. Pros : One never has to select a tank for water as it comes out of all of them.
        2. Cons : A filtering stage is missed out. The pump may suffer because the water level gets lower than the other schemes.

    7. Pump : This clocks up many hours, so select a decent one. My recommendation is always to get a German one such as Grundfos. We had a house fire, where all copper pipes exploded due to the vapourisation of water. The pump survived to run another 5 years, without any maintenance! Most modern pumps are good at detecting an open tap and responding quickly without too much pressure differences.

    8. Treatment : Some sort of treatment is essential. Ideally a 3-stage filter and UV sterilzation. Prebuilt systems are available and are the cheapest way to buy a system. Depending on the size of the house you can use a 10" X 2.5" to a 20" X 4.25". My recommendation would be to use the following combination -
      1. Gradient Density Polyspun 20-micron
      2. Gradient Density Polyspun 1-micron
      3. GAC (Granulated Activated Charcoal)
      4. UV Sterilization
      Note - The gradient density filters trap particles in multiple layers; so they last longer. The GAC removes odour as well as the carbon block but has a better flow rate (or less pressure loss). If you are not using a gradient density cartridge then use a 10-micron in the first stage. I use the Pro Titanium system. [2]

    9. House : The following are recommended -
      1. Pressure Vessel - Modern pumps are good at maintaining steady pressure as more and more taps are open. A pressure vessel, however, makes this even better. It also reduces the number of on/off cycles for the pump.
      2. A bypass pipe (with taps) around the treatment plant, allows you to continue using water in the house if there is a problem with the treatment unit, and while the filters are being changed.
      3. A tap at the inlet of the treatment plant. This stops the water from draining out of the pipes in the house.
      4. A tap and a hose outlet at the end of the treatment plant. This will allow you to flush the fine particles and air in the filters before they get into the house. An alternative is to have a hose tap close to the treatment plant and lower than it.
      5. Pressure gauges at the start, and after each filter. This will allow you to see which filter is clogging up. The plumber may try to tell you that the gauges will show the same value. This is true when no water is flowing. However, they do work while the water is flowing.
      6. To reduce the size of the treatment plant, you can bypass the hose taps and gray water areas such as laundry and toilets. But why bother?

  3. How to Monitor Water Levels?

    If you wish to monitor your water levels without climbing onto the tanks and opening the lids then there are options.
    1. A Float sticking out of the top of the tank with a bright ball on it. They are not storm-friendly.
    2. A sensor in the tank with a display in the house. We use a system called smartwater [3]. There are others such as [4][5].

  4. When to Replace Filters and Lamp?

    Some systems have an alarm that goes off 365 days after it was reset.
    1. UV Tube : This will typically last 15 months before it needs replacing. To keep it simple, suppliers will tell you to replace them annually. For the same reason, I replace mine one a year.
    2. Filter Cartridges : They should be replaced at least once a year. This is because bacteria and slime start living in and on them. If you have just started using filters then check them after 6 months. If they look filthy, then your situation requires a six monthly replacement. If you notice a pressure drop inside the house then it is time to check the filters. To keep it simple, I replace the GAC six monthly and the others annually (unless they look filthy).
  5. How to Replace Filters and Lamp?

    1. Turn off water at the pressure vessel.
    2. Turn off water from the pump (inlet).
    3. Turn off water to the house (outlet).
    4. Engage bypass if you have one and need it.
    5. Turn off power to the UV system.
    6. Have a tray ready under the filter to catch any spills.
    7. Open a tap at a lower height than the system (if any).
    8. Release the pressure on the filters by pressing the red buttons (PR).
    9. Using the spanner remove the filter casing slowly (A,B,C).
    10. Clean the housing with detergent and dish washer brush.
    11. Replace filter as required.
    12. Coat O-ring with vaseline. The rainwater is not hard, it does not have dissolved minerals. This means that it leaches out compounds from rubber, making them brittle. The vaseline also makes a better seal.
    13. Fill the cartridge with water, about a third full.
    14. Replace the casing slowly.
    15. Repeat for each filter.
    16. The UV assemblies are different. Follow the suppliers instructions on how to replace the UV tube.
    17. Slowly open the inlet (tap from the pump).
    18. Press the Pressure Release button from inlet to outlet to remove air. Hold until water starts spurting out.
    19. Check for water leaks, tighten casings if necessary. If there is one, it is usually because the cartridge has not been centered, so remove and centre it.
    20. Gradually open the inlet tap fully.
    21. Open lower tap (if any) or the first tap closest to the system. Run for at least 30 seconds and close it. You may see carbon particles, but you will definitely see frothing. This is just trapped air in the cartridges.
    22. Reverse steps to open taps and turning on power.
    23. Follow the directions on the controller (if any) to reset its timer. Generally you hold the reset button while power is applied and release when it beeps.
  6. How often Should the Tanks be Cleaned?

    The NZ Ministry of Health recommends annual checking and cleaning if necessary. [6] Others recommend every from one to three years. [7][8][9] I think these are overkill.

    You should remove the tank covers and peer inside at least once a year. If they look too filthy, or the water looks discoloured or there is debris floating on top then get them cleaned. Otherwise, I would recommend at least every 5 years. Use a professional company to do this, they will also repair any cracks in the tanks.


  1. Sample Certificate
  2. Bug Buster Pro Titanium
  3. Water Tank Level System
  4. Water Vision
  5. Tank Mate
  6. MoH Guidelines
  7. Water Tank Cleaning-1
  8. Water Tank Cleaning-2
  9. Water Tank Cleaning-3

A Step-by-Step Process to Care for your Rainwater Harvesting

Disclaimer : I am not associated with any of these companies. I do not receive any financial incentives from any of them. These are my honest views based on experience and research.