There is a lot of confusing information about pondless waterfall reservoir size across the internet on many websites, blogs, and videos .... but why? Let's dig into the details
The Popular Pondless Waterfall Reservoir Myth:
"The pondless waterfall reservoir needs to hold two to three times the amount of water that is in motion."
We ask why?
Math is math, water volume is water volume. A gallon of water is a gallon of water, no matter what you contain it within - unless you are containing something other than water along with the water in the storage device. Why build a reservoir that will hold 2-3 times the water in motion? Why store 2-3 gallons of water, when you only need to store one gallon of water? The "myth" relies upon strange math. Let's take a look at the actual math.
To calculate water volume in motion, add the height of the waterfalls to the length of the stream. Then multiply the total length (or water in motion) by the average stream width, and stream depth to find the actual cubic footage of water that needs to be stored underground in a pondless waterfall reservoir. Multiply the cubic footage by 7.48 as there are 7.48 gallons of water in one cubic foot.
Example: For a 3' high waterfall cascading into a 15' long, by 2' wide stream at 2" deep.
Convert the stream depth in inches to feet by dividing by twelve. 2"÷12= 0.17'
Here is the easy math: (3' + 15' = 18' total length, or water in motion) 18'tl x 2'w x 0.17'd = 6.12 cubic feet of water
6.12 cubic feet x 7.48 gallons per cubic foot = 45.78 gallons.
Each combination of one HydroSieve™ pre-filter and one HydroChamber™ together holds 50 gallons of water "above the pump". This means that the pump is pumping water from the space where it sits, and not from the water storage capacity area as with the slotted pump vaults in common rock and gravel pondless waterfalls.
With Russell Pondless Systems™, the pump is below the water storage area - instead of "adjacent" to it like the slotted pump vaults in common rock and gravel pondless waterfall reservoirs. This means that all the water volume that needs to be stored underground is stored "above the pump" inside the Hydro Chamber™. This makes for a much smaller excavation size with zero "guess-work" about the reservoir size and dimensions.
With all the guesswork as to what size the reservoir should be, if you don't follow exact math, you may end up with a reservoir that isn't capable of holding all the water that is in motion when the pump gets turned off. We have seen countless pondless waterfalls like these screenshots from YouTube videos that aren't "pondless" when the pump gets turned off - the water level rises over the matrix blocks, over the river rock, and over the liner edge.
- A pondless waterfall that overflows its basin when the pump is turned off is NOT "pondless"
- A pondless waterfall that pools up at the basin when the pump is turned off is NOT "pondless"
- A pondless waterfall that has any visible "standing water" in the basin whatsoever when the pump is turned off is NOT "pondless"
Russell Pondless Systems™ stores all the water in motion underground when the pump is turned off - making the system truly "pondless"
Manufacturers, retailers, and installers of common rock and gravel pondless waterfalls all repeat the same myth that you need to make your water reservoir 2-3 times larger than the size required to store the water that is in motion. They tell you that because their pump vault virtually sits "within" the water storage area, and not below it as with the Hydro Chamber™. A pump sitting within the water storage area is using water from the storage area to create the water in motion over the waterfalls and stream. Then, when the pump turns off, the water reservoir will over-flow if not "doubled" or "tripled" in size.
Why excavate a pondless waterfall reservoir to hold 91.56 gallons at two times the size needed, or 137.34 gallons at three times the size needed when all you need to store is a little under 46 gallons of water?
The answer is simple, the pump pumps water out of the water storage capacity area, and not its own water area within the slotted pump vault as within the Hydro Chamber™. The slotted pump vault sits almost "adjacent" to the water storage area, and not underneath it. By themselves, slotted pump vaults contain only a few inches of water for the pump in which to work - we call it the "working water area for the pump". Thus requiring water for the pump to be held within the storage area above the pump for proper submersible pump operation.
The following diagram demonstrates the difference between the working water area for the pump between a Hydro Chamber™ and a slotted pump vault:
Whatever amount of water storage area that is used for normal pump operation is storage space that is NOT available for water storage when the pump is turned off. They tell you the reservoir basin must hold 2-3 times the water volume in motion because half of the water storage area is being used by the pump, and not available for water storage when the pump is turned off.
The reason why so many manufacturers and contractors tell you to excavate a pondless waterfall reservoir two to three times the size required is because of water displacement by rock and gravel, and the fact that the pump requires more water to safely operate than the slotted pump vault provides by itself.
The popular slotted pump vault in this diagram by itself contains just 7" of water for the pump in which to operate. The matrix blocks above the pump are for the actual water storage, and the rock and gravel area above the matrix blocks act as the pre-filter for trapping leaves and debris for hand removal.
The slotted pump vault doesn't store water. The rock and gravel stores very little water. So the only "actual" water storage is contained within the matrix blocks inside the rubber lined reservoir basin. The problem is that the pump requires more than just 7" of water to properly, and safely perform. In just 7" of water, any evaporation in the waterfalls will cause the pump to start "sucking air" and pre-maturely burn out, especially when the rock and gravel start to clog with leaves, debris, and algae. If the 7" of water around the pump goes down just a little bit for any reason, the pump will start sucking air and burn itself out.
The slotted pump vault is NOT pre-plumbed for an automatic water fill valve, and the manufacturer's instructions tell you HOW to drill a hole in the unit, but don't tell you WHERE and WHAT LEVEL the actual water level is supposed to be! Why? Do they NOT know where the water level should be? Should you just guess?
The Hydro Chamber™ is pre-plumbed for an automatic water fill valve at the proper height for proper pump function and water storage. Slotted pump vaults create "guess-work" when it comes to where the water level inside the unit should be. Why "guess"? Be accurate with a Hydro Chamber™.
So, in order to keep several inches of water above the pump, the matrix blocks are not being used for 100% water "storage", but 50% for proper pump operation - leaving you with only 50% storage capacity. This is why they tell you to store at least twice as much water as needed.
Russell Pondless Systems™ solve the reservoir basin size dilemma with an easy to install underground pre-filter and water tank system that supports actual math calculations. With Russell Pondless Systems™ there is no need to dig a larger excavation than needed, because there is no need to store more water than necessary.
Russell Pondless Systems™ easy to clean pondless waterfalls are common sense. Install a Russell Pondless System™ next to any brand pondless waterfall, and you will see which one is easier to clean, which one has a lower cost of ownership, and which one can stay as beautiful as the day it was built.
If you are a "Do-it-Yourselfer", doing it right the first time will save you money, aggravation, and time. Do a YouTube search on "How to clean a pondless waterfall" and you will see the hassle of hand-picking debris, pressure washing, and the complete draining of rock and gravel reservoirs you will be avoiding with a Russell Pondless System™.
If you are a contractor, install one of each in your showroom area or landscape for your own understanding, and then use them as a sales tool to demonstrate the differences between the pondless waterfall kits we are talking about.
An easy to clean pondless waterfall that actually remains pondless when the pump gets turned off, or a difficult to clean pondless waterfall that isn't pondless when the pump gets turned off. It is YOUR choice!
