Water Collection System

Water collection system

The water collection system in the garage in its original configuration with a jet pump and pressure tank.

In 2009, after replacing the decaying shingle roof with a standing seam metal roof, we began collecting rainwater off of our house roof into the cistern. This kept us in water for years and still meets our water needs most of the year. With the added burden of doing laundry at home and our increased gardening activities, however, it has become clear that there is a period in later summer every year where the weather just isn’t keeping up with demand. Two years ago we were forced to purchase water and last year we needed to implement “austerity measures” where we were exceedingly cautious about water use. This year demand is even greater as we begin planting fruit trees and companion plantings. With greenhouse construction on the roster as well, demand is only going to climb in future years.

Fortunately, we were already primed to improve our water collection system. A few years ago, I replaced the shingle roof on the garage with a standing seam metal roof when I managed to get a good deal on surplus steel. This gave us an additional 600+ square feet of collection area, which has mostly been going to waste. Around the same time as the roof went up, we managed to secure several Intermediate Bulk Containers (IBCs) that had been used to ship corn syrup to a candy factory. IBCs tend to go for around $100/piece in our area, though we secured these six for $50/piece. The water pump I took out when we redid our household plumbing, a small pressure tank I had lying around and assorted other plumbing components — mostly scavenged or leftover from other projects — rounded out the parts list. One problem that remained was connecting the IBCs, with their bizarre threaded connectors, to more conventional household plumbing components. With calipers in hand, I was able to identify the thread as S60x6 and order the appropriate fittings from Global Industrial. I ordered six in order to bring shipping down from what it would be for four (yeah .. makes perfect sense) and so am ready to adapt the other two IBCs for future projects as well.

Downspout system

The downspouts on the back of the garage — future site of the greenhouse. The lower drain faucet and overflow junction can be seen on the central stack, with the upper faucet visible just to the side.

In designing the system, I knew that I wanted the IBCs to be contained within the garage. Since they are not fully UV-stabilized, I was going to need to cover them anyways and didn’t want to have to build an additional enclosure. The slab floor of the garage provides a solid foundation for the system and although the roof isn’t insulated, the walls are and this provides a good head start should I want to modify the system in future to hold water further into the winter. Though IBCs are stackable, there was an additional problem in that stacking them brought the level of the top IBCs above that of the eavestroughs. It would therefore be impossible to completely fill the top IBCs by gravity alone, even if the lids of the lower IBCs were sealed and a separate stack run above the level of the top IBCs to allow for air pressure equalization.

The solution to inflow came in considering outflow, in that I decided that I wanted to provide a powered option to pressurize water. This would allow not only the use of longer hose runs but would also open the possibility of emptying the system into our main cistern or even pumping it uphill into the currently unused water storage tank in our larger outbuilding. At the same time, there is great benefit to being able to gravity-feed water. Not requiring power every time you need to fill a watering can and being able to provide low-pressure water over long periods of time for irrigation systems are both appealing prospects. In the end, I split the system into top and bottom and provided a centralized junction where I could control the direction and nature of the water flow. The whole system, therefore, can be broken into three main flows: collection, pump-powered, gravity-powered.



When not in use, the inserts for the downspout bypasses can be clipped onto the nearby plumbing.

Under each of the eavestrough outlets, I placed assemblies to collect the flow. The assemblies contain clean-out fittings on the bottom which can be removed in order to allow most of the water to fall straight through. This is useful in winter to avoid building up ice inside the system and also comes in handy any time I want to eliminate the majority of the collection flow. Knowing that the fittings for the clean-outs would be easy to misplace, I cut rings from 2″ ABS pipe and then cut out a slice from the rings so that they could expand to clip over the 1-1/2″ pipe used for the collection system. Using a file to rough up the surfaces followed by ABS solvent, I fused the clips to the backs of the clean-out fittings, allowing them to be snapped conveniently onto nearby plumbing so that they are always in reach when the system needs plugging.

Water Collection System - collection

The lower two IBCs collect water passively from the garage roof.

When the system is active, water is diverted out the side of the collection assemblies and down to a central pipe. The pipe contains a junction part-way up which acts as an overflow spout at the level of the top of the lower IBCs so that the system doesn’t overflow. The bottom of the pipe ends in a T fitting, with one side leading to a tap which can be used to empty the entire system and the other side heading into the garage and connecting to the lower IBCs through their lower fittings. In this way, 500 gallons of water can be collected in the lower IBCs through gravity alone.


Water Collection System - Filling the Top

With the valve to the faucet off and the other two valves on, the pump can be used to fill the top two IBCs with rainwater collected in the lower two IBCs.

In my first attempt at building the system, I used the old pump that was replaced when I re-did the plumbing in our house during our major renovations. Rather than re-connect it to the large, bladder-less pressure tank to which it was originally connected, I used a small bladder pressure tank I had purchased for an abandoned project years ago. Though not strictly necessary for this use, the tank would help to smooth out the pump operation and would prolong the life of the system. The outlet of the pump was connected to the central junction point of the system.

Transfer Pump

Out with the old, in with the … also old, but at least functional. The transfer pump plumbed into the system until a new jet pump can be scrounged.

Unfortunately, the pump wasn’t great when it was removed from the house and had since deteriorated more fully. Although I was able to free up the impeller and re-seal the casing, the corrosion had damaged the impeller itself and the pump no longer generates sufficient pressure. I have added a new jet pump to my scrounging list and will be keeping an eye out at yard sales, auctions, and dumpsters for a cheap or free pump. In the meantime, I hooked up a small transfer pump I had on hand to the system. Although not as powerful as the jet pump, it is still perfectly capable of transferring water from the bottom tanks to the top or feeding a garden hose. It is listed at 35′ head and is happy to pump away in true “little engine that could” fashion. The real drawback of this pump substitution is that the transfer pump is not a pressure pump but is more of a circulation pump — it is not intended to build up pressure in a system and should not be operated with impeded water flow.
Water Collection System - Pump-powered watering

With the valve to the top IBCs off and the other two on, the pump can be used to push water through the outside faucet.

This precludes the use of a pressure switch and pressure tank and requires the pump to be on the entire time you want water flow and off when you don’t; the idea of running a garden hose with a spray attachment or a water timer is therefore out. For now, however, this setup can still be used to move water from the lower collection tanks to the top tanks or to pump pressurized water from the lower tanks to a soaker hose or other open system. Although a watering timer can’t be used to shut off the flow after a given amount of time, the pump itself can be placed on a timer if a set watering time is needed.

Otherwise, the transfer pumps works in a manner similar to the intended use of the jet pump. By manipulating the valves at the junction point, the water from the pump can either be sent to the upper IBCs — preferably during off-peak electricity pricing hours — or to a faucet located on the exterior of the garage (soon to become the interior of the greenhouse).


Water Collection System - Gravity Feed collection

With the valve to the lower IBCs off and the other two open, water can be gravity fed from the top two IBCs through the exterior faucet.

Once in the upper IBCs, the water can be re-deployed using gravity. There is a gain of 0.43psi per foot of elevation in gravity pressurized systems so at this elevation the system can provide 2-3.5 psi at ground level, depending on how full the tanks are. This doesn’t sound like a lot, but it is plenty for filling watering cans or watering plants via a trickle system. The top tanks can also be drained back into the lower tanks for output via the pump or into the main cistern for household use.

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