I planned to build a greenhouse-enclosed tiny home before purchasing my property so I selected my property for good southerly exposure for maximum sun in the growing areas. And it paid off. My greenhouse sits on an almost perfect east-west axis so the growing areas receive sun throughout the day as does the entire interior of the house.  The side-effect of this placement, however, is the shadow cast by the house means the narrow strip between the house and the north greenhouse wall receive almost no direct sun at any time of the year. In reality it receives only an hour or so of west sun just before sunset. As a result, I looked for the best use of that space for my lifestyle and decided to try installing a lap pool.

Although mine might be the first greenhouse-enclosed home project in the world to include a swimming pool inside the greenhouse, mine is certainly not the first swimming pool inside a greenhouse. Meaning, there were some design principles with real-world examples that were partially applicable but none that addressed all main elements and conditions. I have to figure out a lot of this on my own and my project is the first real-world test.

The pool is approximately 6’ wide by 40’ long by 3.5’ deep. I do not want to use chemicals in the pool so am going to try following Organic Pool principles to design a biofiltration system using air, rather than water, to circulate the water from the pool, to ponds where plants will filter the water that is then circulated back to the pool.

Where my project differs from the Organic Pool model, is that Organic Pools have the plant-filtration surrounding the swimming pool but mine has the ponds at each end of a long swimming pool. Just some questions to address:

• How do I ensure water is circulated from the entire pool without a ‘still’ zone in the middle?
• How big do the ponds need to be to hold enough plants to filter ~14,000 gls of water?
• How many deep tubes are needed to move enough water for a healthy turnover?
• How big of an air pump is needed to drive the system?
• Do I need a debris filter since plant material can’t drop or blow into the pool like it could if it were outside?

In situations like this, flexibility is key so I’m trying to also incorporate ways to efficiently ‘tune’ the system without having to drain the pool, replace large parts of the system, or add on expensive circulation or filtration systems after-the-fact.

Like in an aquarium, the Organic Pools system uses rising air bubbles to move water. I don’t know the proper hydrodynamic term or whether the bubbles ‘pull’ the water in their wake or ‘push’ the water out of their way. But, like constraining water inside a garden hose increases the force of the water, constraining the bubble’s path inside pvc tubes increases the force of water being pulled along with the bubbles and the longer the tubes, the greater the force.

To maximize the water movement at the ponds, my system uses as many bubble pumps as I can fit across the edge between the pool and each pond. I’m using bubble pumps that are as deep as can fit in the pool’s depth. I couldn’t find good information on pond pumps so I looked to septic pump sizing guidelines to size the air pump.  

The biggest challenge was ensuring bubbles reach the middle of the pool to eliminate a still zone from, either, the water movement from the pipes at each end is not strong enough to reach the middle, or that the ‘wave’ from each end met in the middle and canceled each other. This is where the soaker hoses come in. The pipe system at each pond include fittings for 2 hoses to attach for a maximum of 4 hoses. I’ll start with only 2 hoses attached to the east pond’s system.

By pumping air through standard garden soaker hoses they turn into ribbons of bubbles. I will place a hose along the entire length of the pool’s bottom south edge and bottom north edge. The hypothesis is this will have a few beneficial effects:

• It will eliminate any still zone by ensuring all water in the pool moves
• It may help to dampen wave rebound from the sides while swimming
• It will ensure constant breaking of surface tension for the entire pool so mosquitoes can’t breed on the pool
• The hoses can be moved to increase or decrease force as needed to optimize water movement

At the time of this post, the pipe systems are installed and water is starting to fill but is not, yet, at a level to turn on the air. Updates will follow in future posts.

Find out more:

Deciding on the pool and ponds

Organic Pool system design principles: David Pagan Butler