Harvesting Rainwater for Home Use

Sooner or later, the demand for clean water always exceeds the supply, but in rural areas, steps can be taken to take the strain off overburdened systems.

by Patrick Walshe

Dry well? Bad water? Is there a potential source of contamination affecting your well?

Water quantity and quality is becoming a major issue as development threatens to outstrip rural water supply in some districts and often reduces the existing water quality at the same time.

In some areas the aquifer is being depleted faster than it can be replenished and will dry up some day. Most of the water districts that rely on surface water are at or near their maximum capacity. Poor water quality plagues lakes and can pose a threat to fish.


Reasons For Rainwater Loss

A number of factors may combine to cause serious losses in the amount of rainwater collected or stored.

  • Roof losses may be caused by evaporation, the direction of prevailing winds, nearby trees, or the roofing material.
  • Gutter losses may be caused by the type and design of the gutters, the slope, their condition, and the down spouts used.
  • Storage losses are commonly due to evaporation, leaks, back-flushing, and human error.

Rainwater reduces stress
Humans are certainly not the only ones to suffer from the water shortage. Rainwater harvesting will take the stress off streams suffering from over- licensed waterways.

In areas of high lot density, ground water extraction can also reduce the flow of small streams. The fish would benefit from some extra flow in the heat of summer as the water quality decreases dramatically with lack of flow and increasing temperatures.

Flooding to increase lake storage capacity has also destroyed wetlands. Seasonal lake level fluctuations are exacerbated by water retention and extraction can also harm fish habitat along the shoreline.

Aside from general water shortages and surface water contamination, there are many other sources of contamination that don't respect property boundaries and can poison your well or stream.

For an area that receives ample rain for most months of the year, cisterns make sense, at the very least for non-potable uses.

This is an area where individuals can make a lot of difference to the environment and take control of their water issues at the same time. It's time we learn from experienced prairie dwellers.

The application of an appropriate rainwater harvesting technology can make possible the use of rainwater as a valuable and, in many cases, necessary water resource.

Rainwater harvesting has been practised for more than 4,000 years, and, in most developing countries, is becoming essential.

Rainwater harvesting is often necessary in areas having significant rainfall but lacking any kind of centralized government supply system (an existing system may well fail in a large earthquake!), or good quality fresh surface water or groundwater.

The advantages of rainwater harvesting

  • Rainwater harvesting provides a source of water at the point where it is needed. It's owner operated and managed.
  • It provides an essential reserve in times of emergency and/or breakdown of public water supply systems, particularly during natural disasters.
  • The construction of a roof top rainwater catchment system is simple, and local people can easily be trained to build one, minimizing its cost.
  • The technology is flexible. The systems can be built to meet almost any requirements. Poor households can start with a single small tank and add more when they can afford them.
  • It can improve the engineering of building foundations when cisterns are built as part of the substructure of the buildings, as in the case of mandatory cisterns.
  • The physical and chemical properties of rainwater may be superior to those of ground water or surface waters that can be polluted, sometimes from unknown sources.
  • Running costs are low.
  • Construction, operation, and maintenance are not labour- intensive.


Construction materials

The collection and storage of rainwater can be maximized by using the correct materials.

  • Storage tanks and their covers can be made of steel, fibreplastic, redwood, or concrete.
  • Roofing should be aluminum or of gal •••vanized material, or metal roofing tiles; nails should be steel or aluminum with rubber washers. And if painted, the paint must be unleaded.
  • Gutters can be aluminum, plastic, or wood, and flashing can be asphalt or rubber.
  • Plumbing can be galvanized, PVC (or better yet, PET), or copper, but any solder must be lead-free.

Here are some questions that you can ask yourself to assess your water quality issues:

Do you have a well less than 16 metres deep?

Has it been longer than three years since you had your well water tested or did your water test positive for nitrate and/or bacteria the last time it was tested?

Is your well downhill from any potential contamination sources (septic system, pesticide, fertilizer, manure, petroleum product storage area, or any other pollution sources)?

Are there abandoned wells on your property that have not been properly plugged and have the pumps been removed? (Pre-1980 pumps may have PCBs.)

Is your septic system less than 30 metres from your well or water body (all year round)? Has it been more than three years since you had your septic tank cleaned out?

Do you regularly use chlorine or chlorine-based products for cleaning (for example, daily application in the toilet bowl)? Do you dump grease, oil, or leftover household chemicals down your drain?

Do you dispose of household products such as furniture polish, paints, stains, and cleaners and/or their containers on your property (including down the drain)?

Do you dispose of used petroleum products, anti-freeze, pesticides or batteries on your property? Are there any of these hazardous products stored near your well?

Do you house livestock or poultry within 30 metres of a water supply system or water body? Do you store manure within 80 metres of a water supply or water body? Is your livestock or poultry facility located up-hill from a water supply or water body?

Do you apply all the fertilizer needed by the garden for the whole growing season all at one time or during intense rainfall? Do you store fertilizer products on your property?

Has it been longer than one year since you updated your nutrient management plan?

Are your pesticides stored on wood, gravel, soil, or on a concrete pad without a curb? Do you have pesticide containers that are damaged, leaking, and/or rusting?

Do you mix, apply or store pesticides within 50 metres of any water supply system or water body?

Is your petroleum storage container less than 30 metres from a water supply or water body? If you have a petroleum storage tank, is it located underground?

Do you lack protection against leaks or spills from your petroleum storage container (no containment system, catch basin, or concrete spill pad)?

Do you need to develop a method of record-keeping to keep track of petroleum use so that you can detect leaks?

* Patrick Walshe is Stewardship Advisor for the Salt Spring Island Conservancy, which recently hosted a workshop on Rainwater Collection, featuring roofing, gutters, storage, maintenance issues, filtration, and disinfection.

* Salt Spring Island Conservancy, 204 Upper Ganges Center, 338 Lower Ganges Rd. Ganges PO Box 722, Salt Spring Island, BC, V8K 2V3; ph: (250)538-0318; fax: (250)538-0319; email: ssiconservancy@saltspring.com

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