rainwater logo


INTRODUCTION:  We offer low-maintenance systems to collect, filter, store, and re-use rainwater for exterior or interior use in residential or commercial structures. In a typical installation, water from all of the downspouts of a building is piped to a central filter that separates solids. The filtered water is stored either in surface or underground storage tanks ranging from a few hundred gallons to many thousand gallons. Specialized pumps, control systems, and disinfection systems draw water from the storage tanks for irrigating landscapes, filling swimming pools or ponds, flushing toilets, and washing clothes. We can also supply rainwater systems capable of producing water suitable for showering or drinking.

REASONS TO HARVEST RAINWATER:  Harvesting rainwater makes sense for a variety of economic and environmental reasons:

• Rainwater is an economical alternative to public water, especially for exterior water uses such as landscape irrigation that require minimal filtration. Although initial equipment installation can be significant, long-term costs are minimal.

• Rainwater can supplement limited ground water resources. With reduced extraction rates, low-yield ground water wells and springs can last indefinitely. Rainwater can also supplement surface water resources threatened by rapidly growing municipal water use. Rainwater collection could significantly reduce water extraction rates from rivers during critical summer months, ensuring adequate water remains to support native ecosystems.

• Rainwater is often the only viable water source in arid regions or on islands where other water sources may be high in salt, limited in availability, or very expensive.

• Rainwater is low in minerals, so it is ideal for laundry, dishwashing, hair washing, and car washing. Since it contains no chlorine, rainwater is also ideal for filling garden ponds and irrigating sensitive plants.

• Rainwater is not regulated by municipal water restrictions. During periods of drought, rainwater can protect investments in landscaping, garden ponds, and swimming pools.

• Rainwater can cause leaky basements, eroded foundations, overflowing sewers, soil erosion, and water pollution. Collecting rainwater can eliminate these problems while eliminating the need for expensive stormwater controls.


watering plants

car washing

washing cars

filling pools

filling pools and ponds


flushing toilets

washing clothes

washing clothes


showering and bathing

MECHANICS OF COLLECTING RAINWATER FROM ROOFS: It’s possible to collect rainwater from roofs, parking areas, pavement, lawns, and almost any other surface, but roofs typically yield the best quality water at the lowest cost. The type of roof surface is of little consequence when rainwater is collected for irrigation or other exterior water uses, but when rainwater is collected for interior water uses, it is preferable to use relatively inert materials such as painted metal, terra cotta tile, cement tile, stone, and elastomeric membranes instead of composite shingles, bituminous membranes, and asphalt coatings. However, rooftop debris usually poses a greater water-quality problem than the roofing material, and water from any roof can be treated to drinking-water quality without great expense.

Gutter and downspout sizing for rainwater collection can follow standard practice, although it is preferable to be somewhat conservative to minimize the potential for overflow due to improper installation or settling. Gutter cap systems can be used to reduce the maintenance of pre-filters, but should not be considered as substitutes for pre-filters.

Rainwater systems are most economical when all the rainwater is conveyed to a central site for prefiltration, storage, and pumping. Piping should be sized using conventional stormwater practice which means 4” pipe will suffice for most residential systems but 6” or larger pipe will be required for most commercial systems. A pitch of one-eighth to one-quarter inch per foot is recommended, but this sometimes poses a design challenge because the allowable burial depths of pre-filters and underground tanks are limited. Pipe connections should be watertight to prevent both water loss and infiltration.

COMPONENTS OF A RAINWATER SYSTEM: A rainwater system should deliver clean water by simply opening a faucet or activating an irrigation valve, just like any other water supply system. In order to be reliable and effective, each component of a rainwater system must be specifically engineered for rainwater collection since off-the-shelf water system components are rarely suitable. Rainwater system components can be functionally classified as prefiltration, storage, pumping, treatment, backup integration, and measurement and control, each of which is described separately.








post treatment


measurement + control


backup integration


return to top of page