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100-Gallon First Flush Tank

100 Gallon First Flush Tank
Check out additional color options & sizes available! See list of specs & features below.

This tank is a great addition to a large-scale rainwater system! View our Rainwater Collection Chart to see your potential.
List Price: $262.37
Our Price: $204.95
You Save: $57.42

Product Code: PM100FFHW4


Description Style Differences Information

Our line of First Flush Tanks includes options from 100 to 500 gallons to fit whatever rainwater-catchment area you have. With proper plumbing, clean rainwater will bypass the First Flush Tank and flow into your primary storage tank or tanks.

Using a rule-of-thumb of 10 gallons of runoff capacity for every 1,000 square feet of roof, by the time your 100 Gallon First Flush Tank has been filled, the water coming off of your 10,000-square-foot-or-smaller roof will be much cleaner and for diversion and storage in your Rainwater Harvesting Tanks.


Rainwater is one of the purest sources of water available anywhere, and nature won't even send you a utility bill for it. But what's on your roof may not be quite so pristine, especially if it's been a while since the last rainstorm. Leaves and dust, pebbles and pigeon droppings—none of that belongs in your drinking water.

Installing a First Flush Tank to divert and collect the first bit of dirty runoff coming from your roof allows you to keep the clean rainwater you want to use, separate from the junk.

All of our tanks offer a five-year warranty and come standard with a four-inch inlet on top flat, 1.5-inch plug for drainage as well as a 0.75-inch fitting for a hose spigot. Tanks are available in 13 colors with built-in UV inhibitors that prevent color fading and breakdown from harsh sunlight.

You should use a 100-gallon First Flush Tank if:

  • You are building a large-scale Rain Harvesting System with a 10,000-square-foot or smaller collection area
  • Tree coverage hanging over your collection area creates abnormal amounts of debris or bird waste
  • The system brings rainwater indoors for regular consumption or use in appliances

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