Converting a Swimming Pool to a Rainwater Tank

Spending more time tending to your pool than swimming in it? Tired of toxic chemicals and endless maintenance? Now you've got options.  

Now more than ever, smart people are thinking sustainably about the resources they use and how much money goes "down the drain" every month.   If you're the proud owner of a swimming pool, then you know they are one of the biggest drains of time, energy and money in the maintenance of your home and landscape.  Why not make your swimming pool work for you?  

Rainwater harvesting technology has come a long way in the past 5 years.  Using a simple but robust technology, your swimming pool can be utilized as an underground rainwater harvesting cistern.  Water collected from your rooftop is filtered, stored and pumped up on demand to satisfy your water demands.  The top of the tank is brought to ground level and can be covered with grass, stone work, a wooden deck, or any other landscape material you'd like.  

We receive many requests for information on swimming pool conversions every week.  We've found that there are some common questions pretty much everyone has about the process.  Please take a look at this list of questions and let us know if you have others.

If you're ready to start a project, please contact us today!
 

Frequently Asked Questions

How much does a pool demolition cost?

Perhaps you've simply stopped using your pool because the kids grew up, the endless maintenance has gotten the best of you, or the cost has become too much to justify.   Most people facing these circumstances initially consider the possibility of having a pool demolished, backfilled with soil and made into a lawn.  The cost to have a pool "demo'd" can be significant.  Hiring a general contractor to break and remove the coping, remove the filters systems, cap the electrical lines, backfill the pool and bring up to grade will cost somewhere in the neighborhood of $3,000-$10,000 for a family size pool, depending on site access, size of the pool, cover material plus other considerations.

Can all swimming pools be converted to rainwater cistern?

The short answer is yes.  Even if your pool is oddly shaped, has different depths or doesn't currently hold water, we can almost certainly find a way to convert your pool to a rainwater cistern.  

What can I use the water for?  

Water collected from your roof can be used for many different purposes.  The most common are landscape irrigation, wash water and water feature refill.  In some circumstances, water from an underground rainwater tank can be used for indoor purposes.  However, the materials used to create the internal structure of the rainwater tank are often made from recycled plastics, which is good for the environment, but provides water for non-potable uses only.  If you require drinking-water quality from your rainwater tank, we have a solution for that too which involves using NSF certified drinking water components and filtration systems.

How much water can I collect/save?

There are two values used to calculate how much water you can potentially save annually by collecting and recycling rainwater.  

1. Collection Area- The total square feet of your roof "footprint" (also referred to as your "total slab") you will collect from..  A common household may range from 1,500 to 3,500 square feet.
2. Annual Rainfall- How many inches of rain will fall on your roof on average during a year?  To find this, Google "annual rainfall (your city)".  

Wondering exactly how many points a rainwater harvesting system can provide towards a LEED certification? 

The U.S. Green Building Council, founded in 1998 and working to promote buildings that are environmentally responsible, is starting to address the regulation and evaluation gap, and has established the LEED (Leadership in Energy and Environmental Design) ranking system.

LEED evaluates commercial buildings and provides a verifiable means of demonstrating that a building is “green”. Under the LEED certification program, there are four classification levels or ratings: Certified, Silver, Gold, and Platinum. The levels are based on points awarded for the design, construction, and operation of a building. The Certified level requires a minimum of 26 points; Silver requires 33 points; Gold is 39 points; and Platinum requires 52 points out of the 69 total possible points. (HarvestH20)

A building with a rainwater harvesting system has the potential to garner up to seven LEED points as follows:

• 1 point for installing above-code measures that result in 20 percent water savings.
• 1 point for installing above-code measures that result in 30 percent water savings (typically waterless urinals or other unusual measures).
• 1 point (innovation credit) for installing above-code measures that result in 40 percent water savings (rainwater harvesting system or other water re-use).
• Up to 2 points for storm water reduction (storm water management practices).
• Up to 2 points for water-efficient irrigation
• 1 point for reducing the project’s sewage generation from use of potable water by 50% or more.

One of the most common questions regarding rainwater harvesting is:  What happens if there is a drought and my tank runs dry?  This is a very good question and illustrates how important water is to us.  The simple answer is: The same thing that happens if your well or municipal water source runs dry- you have to find more water.  However, unlike with municipal and well water, with a rainwater system you know exactly how much water you have and can ration accordingly until the next rain.  Most people assume that their municipal water source is endless and will never run dry, however, studies show that over 70% of people do not even know where their water comes from, let alone the level of the reservoir.  In reality, if the catchment area and storage tank in your rainwater system are sized appropriately, you will have an abundance of water to last through normal drought events and can always have water delivered to your storage tank if needed- which is not possible with a well or city water supply.  More often than a shortage of water, our customers request the need to have more storage capacity for the abundance of rainwater they are collecting.

If you need your water tank to refill partially from the municipal grid or a water well before it goes dry, there are many level control solutions available to maintain a pre-determined level of water in the tank.

A professionally installed rainwater system will include a collection system, adequate filtration, a holding tank, and distribution system.  Costs vary greatly between a small residential system and a large commercial system as well as between the cost for above ground and under ground tanks. 

For Reference

• A small residential system, collecting water from 500 sq. ft., with a 1,000 gallon above ground plastic tank.  Starting at $2,500 installed.
• A large residential system, collecting water from 2,500 sq. ft., with a 5,000 gallon above ground metal tank. Starting at $10,000 installed.
• A small commercial system, collecting water from 8,000 sq. ft., with a 20,000 gallon above ground metal tank. Starting at $25,000 installed.
• A large commercial system, collecting from 12,000 sq. ft., with 25,000 below ground storage tank. Starting at $75,000 installed.

Tanks
When considering the cost of a rainwater system, the tank is a large portion of the total cost.  While everyone would like to have enough storage so that the tank never overflows, many factors come into play such as water demand, rainfall patterns and cost.

A general rule is to multiply your catchment area by 2 so that you can collect 4 inches of rain in one week.  For example a 2,000 sq. ft. home would be paired with a minimum 4,000 gallon tank.  A 10,000 sq. ft. building = minimum 20,000 gallon tank.  In cases where a rainwater system is the only source of water or there are extended droughts, a larger holding tank is required.

The cost of a tank depends on its size, quality, material, and site preparation.  Shipping can also add significantly to the entire cost of placing a tank.  Once you know the approximate size of tank you'll need, choose above or below ground and your preferred material.

Choosing the size of tank required for project can be summed up in three steps:

1. How much water can you collect and when does it fall? 
2. What is your monthly water demand and how does it change throughout the year?
3. What is your budget? A water tank is around 50% of the total cost of a system.

For every 1,000 square feet of catchment area you have, you can potentially collect 620 gallons of water for every inch of rain.

Remember:

• Only the fooprint of your catchment surface matters when calculating collection potential.  Roof slope is not considered in this equation.
• In reality, some water is always lost to splashing, evaporation, and roof washing. 
• The simplest way to calculate actual collection volume is to divide the square footage of your roof by 2.  So, a 2,000 sq. ft. catchment area will collect 1,000 gallons per inch of rain.