Lorne, a consultant working for ICC on the irrigation and rain water harvesting stopped by to discuss our choice of cistern tanks. They are coming from California via railroad, which is more energy efficient thank truckng, if slower.
The original plan had been two large tanks at opposite corners of the property. But after considering the cramped space and the House's operational needs, we decided to set both tanks off the southeast corner. One tank will fill; overflow will drain into the second tank which will hold the pump. This configuration allows us to use only one rainwater harvesting pump instead of the two we'd originally planned. The simplified system will be less prone to malfunction - so it will be more sutainable.
Additional issues with the system are the rather large hole the tanks require, the manhole for maintenance access to them, connectors for the inlet pipes coming off the gutters, and the underground wiring for the pumps.
The hole the tanks go into will be on the order of 20 feet deep, 6 feet wide and some 20 or 30 feet long. Yeah, big holes. Since the foundation has been dug around, exposing it for the addition of insulation, now is prime time to dig for the water tanks.
The pipes that will bring the water from the gutters are to be buried below the frost line - we want to go four feet deep. To maintain a steady tilt down towards the tank - so if we put those at the back of the house four feet down, the slant required will put the tanks pretty deep. Which is fine, but it means we'll need to have a deeper manhole connection than the tanks normally come equipped with.
The pumps we've considered have a 20 foot cord attached. This will get us to the surface from the likely depth of fifteen feet, but that puts us into the middle of the front garden. Running an extension cord isn't an option, so we will have the electrical guys from Southside wire a junction box. We chose to put the junction box on the side of the house and find a pump with a longer cord that will reach the house.
All in all the rainwater stuff is shaping up - but it's going to be hard to wait for the tanks to be delivered so we can deal with our amended design in real terms.