Rainwater catchment systems are extremely common on the East Side of the Big Island. For many homes in Puna, Volcano, Mountain View and surrounding areas, catchment is the primary household water supply.
A catchment system is relatively simple, but every part of it matters. Water travels from the roof through gutters and piping, into the storage tank, and then through pumps, filters and treatment equipment before reaching the faucet.
Problems anywhere along that path can affect water quality.
Here are some of the most important parts of a Big Island rainwater catchment system to check and maintain.
1. Keep the Roof and Gutters Clean
Your roof is the collection surface for your drinking water, so keeping it clean is an important first step.
Watch for:
- Leaves and other organic debris
- Bird or rodent activity
- Damaged roofing
- Standing water
- Clogged gutters and downspouts
Gutters should be kept clear so rainwater can move freely into the catchment system rather than collecting debris or overflowing.
2. Check the First-Flush System
A first-flush diverter is designed to keep the first portion of roof runoff from entering the catchment tank.
That initial runoff can contain dust, leaves, bird droppings and other material that has accumulated on the roof between rains.
If your system has a first-flush diverter, make sure it is functioning properly and is being emptied or maintained as required by its design.
3. Inspect the Catchment Tank
Periodically look over the tank itself for obvious problems, including:
- Leaks
- Corrosion
- Damage to the tank or liner
- Loose or damaged covers
- Sediment accumulation
- Vegetation growing against the tank
A secure cover is especially important because it helps prevent debris, animals and insects from entering the stored water.
Catchment tanks also need periodic cleaning. The appropriate timing depends on the system and how quickly sediment accumulates rather than simply following one schedule for every tank.
4. Look at the Piping Between the Roof and Tank
One problem I commonly see with Big Island catchment systems is piping that travels underground between the house and the tank.
This may look better, but ideally the water should be able to drain continuously toward the tank without becoming trapped in low areas of the piping.
Water that remains trapped between rains can become stagnant and may contribute to algae or microbial growth.
Look for sagging pipes, low spots or other areas where water may not completely drain.
5. Make Sure the Tank Cover and Screens Are Secure
Openings into the tank should be protected.
Check that:
- The tank cover is secure and undamaged
- Overflow openings are screened
- Vent screens are intact
- There are no obvious openings where insects, rodents or debris can enter
Mosquito control is particularly important in Hawaiʻi, so don’t overlook small openings or standing water around the catchment system.
6. Maintain Your Filters and Water Treatment Equipment
Most residential catchment systems use several stages of filtration and treatment.
Depending on the system, this may include:
- Sediment filters
- Carbon filters
- UV treatment
- Other filtration or disinfection equipment
Filters need to be replaced according to their condition and manufacturer recommendations. UV systems also require maintenance, including periodic lamp replacement.
A treatment system only helps when it is operating and maintained properly.
7. Watch for Animals and Pests
Because your roof is part of the water collection system, animals can affect catchment water before it ever reaches the tank.
Birds, rats and other animals can leave biological contamination on the roof or around the system.
Keep vegetation under control around the tank and look for signs of animal activity, damaged screens or openings into the catchment system.
8. Pay Attention to Changes in Your Water
If your water suddenly looks, smells or tastes different, don’t simply assume the problem will go away.
Changes can be caused by sediment, filtration problems, plumbing, minerals, treatment equipment or other conditions.
It’s also important to remember that water can look, smell and taste perfectly normal and still contain contaminants that cannot be detected with your senses.
9. Have Your Catchment Water Tested
Water quality testing is now the primary service we provide at Big Island Home Inspectors.
For residential rainwater catchment systems, our professional laboratory testing includes:
- Total Coliform
- E. coli
- Turbidity
- Copper
- Lead
If you are wondering what each of those tests actually tells you, we put together a more detailed guide:
What Should You Test Your Catchment or Well Water For on the Big Island?
That article explains the difference between testing for health-related concerns and testing for issues involving taste, odor, appearance or minerals. It also explains why catchment water and private well water require different testing panels.
When Should You Consider Testing Catchment Water?
There are several situations where water testing can be especially useful:
- You’re purchasing a home with a catchment system
- A lender requires laboratory water testing
- You don’t know when the water was last tested
- The catchment tank has recently been cleaned or repaired
- The filtration or UV system has had a problem
- The water has changed in appearance
- You’re concerned about bacterial contamination
- You want a baseline of the water quality in your home
We professionally collect the water samples at the property and deliver them to a laboratory for analysis.
Schedule Big Island Catchment Water Testing
A Catchment System Needs Ongoing Attention
A rainwater catchment system isn’t something you install and then forget about.
The roof, gutters, piping, storage tank, filters, treatment equipment and household plumbing all work together as part of the water system.
Keeping those components maintained and periodically testing the water can give you a much better understanding of the water you’re actually using in your home.