PLUMBING 101
Lenny is quoting some very common mis-information that I hear very often.
Remember the previous quiz where there is a water tower - say 100 ft high to the water level, and there are two pipes - a 10″ and a 1/2″ connecting the tower to “the ground level” With no water flowing, the pressure is exactly the same = 100 ft of head. Now, the weight of the water in the two pipes is very, very, very, different!! But the PRESSURE is the same.
This is hard to understand. So, lets take a pile of identical paving stones - and assume that each one is identical, is 12″ x 12″ and each weighs 10 lbs.
We take 16 of them and spread them out one layer thick, touching each other, making a 4 ft x 4 ft square on the ground. Each paver is putting 10 lbs per square foot of PRESSURE on the ground. 16 pavers = 160 lbs total weight, over 16 sq ft = 10 lbs per sq foot.
If we now take them and stack them on top of each other = 16 high = 160 lbs on 1 sq ft = 160 lbs per sq ft.
Now go to the 2 pipes under the water tower. Ignoring the pipes themselves, and assuming that they are PVC schedule 40 for ease of me doing this, the 1/2″ pipe has a cross-sectional flow area of .057 sq in and the 10″ is 78.9 sq in.
So the 10″ holds 1384.21 times the water that the 1/2″ does. So it is heavier by 1384.21 times. BUT, the ground that the 10″ pipe rests on is also 1384.21 times larger. So the pressure PER SQUARE INCH is the same. The pump only cares about PRESSURE.
So, lets assume a small pump sized for the 1/2″ pipe but capable of pushing water up 100 ft high. Assume that it is merrily pumping a single foot per minute = not very much water, but steady. Now attach that same pump to the 10″ pipe - it will still pump the same gallonage per hour because the pressure is the same. But now it only rises 1ft divided by 1384.21 = imperceptible, but the same steady flow. It is not the WEIGHT, it is the PRESSURE.
The larger the pipe, the more water will fit thru it. The less the backpressure will be. When in doubt, oversize the pipe. In our current example of the 4200 gph pump - attach it to 5 ft and 50 ft lengths of Coastal Contractor hose of different sizes (These are real numbers). (expressed as GPM/GPH)
5 feet 50 feet 1-1/4″ 60/3600 29/1740
1-1/2″ 70/4200 47/2820
2″ 81/4860 63/2780
And, obviously, 2-1/2 and 3″ would have delivered even more water - but when these tests were run on the Leader Ecosub 420 (Cal PU3900) we did not have those big sizes.
SO, for example, 50 ft of 1-1/4″ = 29gpm and 5 ft of 2″ = 81gpm….. Hmmmmm. For the same pump and virtually the same electric bill.
:-)
Bill
Category: Ponds-Koi
