large waterfall

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carlos31

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Oct 18, 2007
104
Central Texas
I have a large waterfall made of natural rock. Its 6.5 feet high and 7 feet across. The water outlet is a slot about 5 feet wide and 3/4 to 1 inch tall.

Forgetting pipe capacity and pump sizing for a minute, can anyone advise on an adequate flow rate for a waterfall this size? I am trying to create a strong, gushing flow; no trickling. I am hoping that someone else has a large water feature and can comment on how many gallons per minute their waterfall uses and if they are happy with that volume of water.

thanks,
 
Waterfalls can have a wide range of flow rates, giving a wide range of different effects. So it all depends on the effect you are trying to achieve. Flow rates can vary from 5 GPM per (horizontal) foot of waterfall all the way up to 75+ GPM per (horizontal) foot of waterfall.
 
Just to close the loop on this thread for those who may need some information, I hooked my waterfall to my 4x160 to get an idea of what flow rates would look good. I have a flowmeter on the line to provide the GPM. I didn't hookup the dedicated waterfall suction plumbing though; I just used the drain and 3 skimmers. I was bypassing the filter during this test.

4x160 Intelliflo

speed 4 130gpm niagara falls - loud and rushing
speed 3 95gpm not that much different from speed 4
speed 2 50gpm soothing and gentle but definately not trickling


I like the niagara falls effect but my wife thinks it reminds her of a water ride at Disney; she likes the more tranquil 50 gpm.

Bottom Line - It took alot less gpm than I thought to get a great looking waterfall. This tells me that some of the really weak falls I have seen on other pools with dedicated 2 or 2.5 HP pumps must have really bad hydraulic setups. The water opening on my waterfall is 5 feet wide so you can see that generally 10 gpm/ft is adequate and 20gpm/ft is pretty lively.
 
landmark218 said:
What is the operating pressure on your filter? Our pool is just over a month old and I can't get the pressure below 20 psi when running at 3450 rpm. I've backwashed and recharged the filter twice already when the pressure reached 30 psi.
Click to expand...

Running the intelliflo at full blast is the equivalent of a 3 HP whisperflo which should easily be pushing more than 100 gpm (optimal for your filter), so I'm not surprised at the psi.
 
When I played with the waterfall I was bypassing the filter and didn't take any readings but, here are my readings when running the pump in normal mode.

speed 4, 120gpm, psi=13.4, hg=-8
speed 3, 85gpm, psi=7.4, hg=-5.5
speed 2, 50gpm, psi=2.4, hg=-3

psi is taken from a gauge on the inlet to the filter (not the filter gauge) and hg is from a gauge on the suction side of the pump. The psi gauge on top of the filter usually reads about 3psi lower than the inlet gauge.

After I backwashed a couple times, my pressure calmed down. It could be the plaster dust or it may have been that I was overcharging my Quad DE100. If you aren't weighing your DE with a scale; I suggest you do so. Do not trust the scoop or the coffee can method. See the link.

http://www.troublefreepool.com/de-filter-start-up-confusion-t9610.html
 
carlos31 said:
When I played with the waterfall I was bypassing the filter and didn't take any readings but, here are my readings when running the pump in normal mode.

speed 4, 120gpm, psi=13.4, hg=-8
speed 3, 85gpm, psi=7.4, hg=-5.5
speed 2, 50gpm, psi=2.4, hg=-3

psi is taken from a gauge on the inlet to the filter (not the filter gauge) and hg is from a gauge on the suction side of the pump. The psi gauge on top of the filter usually reads about 3psi lower than the inlet gauge.
Click to expand...

How many of your 27(!) returns did you have open?
 
Those numbers are with all returns open, except the slide. If I close the wall or floor returns it just increases velocity to the remaining open returns and total gpm goes down slightly.

However, I may need to take a second look at the numbers since I noticed 40gpm at speed 2 this morning instead of 50. I may not have waited until things settled down enough after changing speeds or it may have something to do with the 20 degree temperature drop we had last night.

This will probably be my regular speed since 40gpm gives me 1.5 turnovers a day. I intend to run my pump 24x7 at a low speed. However, I anticipate solar being in my future. So, I need to run the pool fulltime and handle solar but also run the waterfall and a TurboTwister slide on demand.

I have not figured out a pump strategy yet. It seems that I can run the waterfall and the entire pool from the 4x160 EXCEPT the slide. The slide is a back breaker. 180 feet of 1.5 inch with 9 feet of vertical rise. It just adds to much head to the system. So I need pump to run just the waterfall and slide return; probably a Whisperflo.

Does anyone know if I can change water velocity on a regular pump (whisperflo) by plumbing in a loop with a ball valve so that velocity can be reduced by opening the valve and redirecting some water from the return side to the suction side?

Note: I will make an effort to post some pictures in the next couple of days. I tried it once but they are too big; I need to sign up for Photobucket or some similar site.
 

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carlos31 said:
Does anyone know if I can change water velocity on a regular pump (whisperflo) by plumbing in a loop with a ball valve so that velocity can be reduced by opening the valve and redirecting some water from the return side to the suction side?
Click to expand...

Yes you can use a bypass but that will probably make for a very loud pump as adding flow to the suction side will reduce the effective head loss and will increase total flow in the pump. It might work better if you bypassed to a return.

An alternative is to simply add a valve on the output of the pump and the more you turn it off, the higher the head loss will be and the lower the flow rate. Pumps tend to run quieter with higher head loss. You can also use a valve stop to prevent closing it off all together
 
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