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Q and A

How much rainfall do we get in a year in the San Juan Islands?

Most areas get between 25 and 30 inches per year. I estimate 20 inches of usable rain per year when I am figuring out storage capacity.


What is the best type of roofing material to use for collecting rainwater?

A tin roof works best and is easiest to clean, but any material will work to catch rainfall. The secret is to keep the roof free of moss, leaves, and needles and to keep the gutters clean. Don't use any moss killing products on the roof. If in doubt about the quality of the water I like to send a sample in for analysis.


How much water will I use in a month?

This depends on many factors. How many people are using the water? Do you have a dishwasher and washing machine? Do you water the garden with this water? Will you have visitors this summer? Many people can get by on 50 gallons a day. Most people can get by on less. Some people use 50 gallons to take a shower. You have to keep track of when you use water and how much you use. Most dishwashers, washing machines, and toilets will tell you somewhere how much water per cycle or flush. Keep track of your consumption for a day or better yet a week and figure from there.


How much storage capacity will I need?

This depends on your consumption. Once you figure that out you can estimate how much water you will need to get you through the dry periods. The San Juan County Health Dept. wants to see a storage capacity of three months of your consumption to get you through any extended dry period. This is a good rule of thumb but not always obtainable. If you do run out of water you can rely on a water hauler to fill your tanks. This is expensive if you have to do it often. In the long run it is less expensive to put in more storage if your roof can supply the water.


How much water will I catch off my roof?

This depends on the square footage of the building including the amount of overhangs of the roof. I conservatively figure that for every one inch of rainfall on a roof of 1,000 square feet, (that is a building 25' X 40'), you will catch 600 gallons of water. So in an year of 20" of rainfall you would catch 12,000 gallons of water.


What will it cost to put in a rain catchment system?

This depends on many factors. Usually I can get 5,000 gallons of storage capacity, pump, filters, and ultraviolet treatment for less than the cost of a drilled well. If you are just using the water for gardens, or livestock, or fire protection you do not need as many filters or treatment. Call or e-mail me and we can discuss your system in more detail.


Can I drink the water off the roof?

Only after filtering and treatment! Rainwater after treatment is excellent quality water, usually better than well water.


Can I use rainwater for bathing and washing clothes?

Rainwater is soft water. It does not have the minerals that ground water has picked up. Soaps will work better in rainwater. People tell me that rainwater is much nicer for bathing and their clothes come out softer from the wash.


What about large tanks for community systems or one large tank instead of using smaller tanks?

See the page on larger storage tanks. Usually household systems can get by less expensively by using the 2,500 gallon poly tanks rather than one large steel tank.


If I buy one tank now can I add another tank later?

Yes. The poly tanks are easy to link together. You will save on site prep and installatiion costs if you did it all at once but it is not necessary. (Usually when people come to me and buy one tank it fills up so fast that they come back for more storage so they are not "losing" all that water.)


How big are these tanks? What color are they? And can they be buried?

My standard tank and the most economical gallons per dollar is the 2,500 gallon poly tank. It is about 8' diameter and 8' tall. I get them in a dark green color. They can be buried about 2 feet to get the piping underground to keep from freezing. I have other tanks that can be completely buried but they cost more. Usually fencing or screening with plants will hide the tanks from view.


What kind of filtering and treatment do you recommend?

I have a standard package of filters and an ultraviolet treatment that works best for most systems. This will last for a year in most cases without any maintenance. Each system is unique so I do size the system to the site. Call for a discussion of your needs.


My well water stains the sinks and toilets. Do you have filters to take care of this?

Yes. I recommend getting a complete water analysis to determine the chemical content of your water, then I can design a filtering and or treatment system for your specific water problems.


My well water smells like rotten eggs and tastes bad. What causes this and can you take care of it?

The smell is from Hydrogen Sulfide gas present in the well water. There are a number of ways to deal with this depending on how much gas is present in the water. You may notice that letting the water stand in a pitcher or glass for a time will remove some of the smell and help the taste. Spraying the well water into a storage tank lets the hydrogen sulfide gas escape by atomizing of the gas during spraying and also by sitting in the tank before use. There are also treatment systems available to actively remove the hydrogen sulfide gas from the water. Current thinking is that the gas in small quanities is not harmful just obnoxious.


Do you put in any tanks for fire protection?

Yes. We can install a tank for fire protection and we have the fittings to match up with the local fire department. We can also install fire protection fittings in an existing tank.


What about all that space under my house? Can I put a tank there?

Yes. See our page on Pillow and Bladder tanks.


If I am building a house can we design and build it to better accomodate rainwater catchment?

Yes. Designing a new house or garage to accomodate rainwater catchment will make it easier to put in a system. No matter what your water source, collecting rainwater is the smart thing to do.


What does the local Health Department say about rainwater catchment?

The San Juan County Health Dept. has very environmentally friendly policies about rainwater collection. They understand that there is a limited amount of groundwater and anything we can do to preserve the water table is needed. San Juan County has guidelines to follow in designing a rainwater catchment and water treatment system. See the page on links for a link to their site or call the San Juan County Health Dept. at 360-378-4474 for more information.


Where can I get a chemical and bacterological analysis of my water? And do you do that service?

I send water samples to Edge Analytical off Highway 20 west of Burlington. They do an excellent job. You can take or UPS your own sample or we can do it for you for a fee. The phone number for Edge Analytical is 1-800-755-9295.


What is the best way to contact us?

Our office hours are from 8:00 AM to 5:00 PM Monday through Friday. But as with most business in the San Juans we are here after hours and on the weekends. Many times we are out in the field. The best thing to do is call and leave a message and we will get back to you. You can e-mail me also at michaeld@rockisland.com


PurRain Corp.
P.O. Box 34, 155 Channel Road, Deer Harbor, Washington, 98243, US
phone:  360-376-2552  fax:  360-376-2552

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