We want to capture rain water on our property. Our house’s roofs, the balcony and the deck cover roughly an area of 3,000 square foot.

We don’t currently have a drainage problem, it’s more about designing the drainage thoughtfully with a future water tank in mind. The house is currently being remodeled, no requirements for LID have been set for us, but we want to do our part anyway.

Details are up for discussion, but we are thinking:

• 10,000 Gallon underground water tank
• Position it in the backyard between the house and a future fresh water pool
• Use the captured rain water to top of the pool and and our graywater system (Hydraloop H600)

Reference Images

Our home is facing south. There is a slope from west to east and also down beyond the northern end of our lot. We cannot drain north or east as there are other properties and mud slides are a problem in our neighborhood. The property itself is sloped towards south (the street).

showing the neighboring lots

We plan for a fresh water pool in the backyard and for an underground rain water tank.

Site survey of the property (North pointing left)

We are thinking to position the underground water thank in the backyard so that gutters and decks can all drain towards it. Drain overflow water on the east side of the house towards the street

Instead of making a separate underground tank right next to the house as shown above, I think it will make much more sense to put it right next to the pool instead. For one I learned that digging a hole right next to the house’s foundation is not possible, we need a clearance of twice the depth we excavate. And I think we could benefit from creating a single bigger structure when doing the pool. Basically get a permit for a pool with twice the width, but then cover half of it up and put in a wall between the two chambers.

I could imagine to make the pool twice as wide with two chambers. One will be open for swimming as shown above, the other will be closed and work as a water tank. Part of it could also be covered by planting area for natural filtration. The water tank chamber could be filled out with eco boxes like in this video for structural integrity.

Another thing I learned from German installers and owners of natural swimming pools / ponds is that rain water shouldn’t be used directly for organic swimming pools. It brings toxins from the atmosphere, the roof, and gutters, lacks minerals, and can unbalance the PH value of the pool as the PH value of rain is 5.5 or less. But in our case, I’d really like to come up with a system where rainwater can be cleaned and treated so that it’s safe to use with the natural swimming pool system.

Questions

• Can we put in drainage that collects all water from roofs, balcony, and deck and directs it to the backyard before it drains it to the street? That way we can add the water tank in future
• Will we need to add a retaining wall if we want to put the cistern in the backyard? We plan to dig 5’ deep as to our understanding that doesn’t require a permit, but we are open to alternatives.
• If we treat the rainwater to make it safe to drink, can we use it as water source for our house?
• Would it be a problem / how much of a problem would it be if machinery for digging couldn’t get to the backyard? We are planning for front-yard landscaping as well, but once we do, a small digger couldn’t simply drive to the backyard any longer.