A Medium Sized Rain Water Collection System -- Performance & Cost

We have not had a whole lot of time to see how the new rain water harvesting system does, but here is a report to date on how well it has worked out, what the water savings are, and how the cost and rewards for the system have come out so far.


I'll post a further update at the end of the season.



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We had a fairly wet spring (for our area), and the tank filled up before we really needed any water from it.  There was a bit of overflow from the full tank, but not a whole lot.

We have started to use the water for the garden as needed, and it appears that with our small garden it will go for some.  While rain is light in the mid summer here, we do sometimes get showers which should help to bring the tank up.  The CLIM20 report says that on average we should pick up a total of 4.7 inches over July, August and September -- this would  add another 2200 gallons over the summer to add to the 2500 gallons already in the tank at the end of June.

At least to a first cut, the tank size seems about right for what we wanted to do.

The delivery pump system has been through a few watering's and is working fine. 

So far, the water is staying very clean -- it looks good enough to drink.

The overflow system has done its thing OK, although it has not been tested yet by a really heavy rain with the tank full.


I did not keep track of all the details, but here is a rough go at the cost:

Item Cost Notes
Tank (2500 gallon, dark green polyethylene tank) $800 See note on shipping below
Gutters $300 (?) Professionally installed seamless aluminum gutters.
Pump (half horse from Northern Tool) $50  
Pipes and fittings $200 Mostly PVC pipe
Electrical supplies for outlet $15 Added new outlet
Total $1365  

We had the tank shipped to us, and this cost about $300(?) -- had we planned ahead we could have had the local AG store order the tank for us with one of their regular orders and avoided the shipping. 

Payback and Rewards

In our case there is very little monetary payback.  About all we save is what it would have cost to pump water from the well and some wear and tear on the well pump -- not a large amount.

For our system used between March and October, the average rainfall is 15.9 inches and that would result in (15.9 inch)(460 gal/inch) = 7300 gallons collected.  If we were inside the Bozeman city limits and on the city water system, we would pay about $50 for the water and associated sewer charges for the 7300 gallons.  Some places are quite a bit more expensive, and water rates are going up rapidly in many areas.

So, clearly, we did not do this with saving money in mind.  For us the rewards are using less well water, which is getting to be important around here, and having an independent supply of water on hand for emergencies.

The 7300 gallons of water the system saves is significant, and we have taken steps inside the house to reduce water usage, which may be saving a similar additional amount of water.   But, the remaining elephant in the room is watering the lawn -- I don't even want to estimate how much water we use for this.  We really need to work out more of a native and low water usage landscaping scheme.  Anyone know any good references on native plant landscaping for the Rockies?


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Comments or questions...?


Gary July 5, 2011