Combining pumps in parallel and series

[combatwombat]

I don't know if this is such a groundbreaking idea, but it's kind of blowing my mind:

Basically, you can plumb two pumps in parallel to get double the flow at the same head or plumb them in series to get the same flow at double the head.

From what I know about electricity and how you can manipulate circuits to get whatever amperage or wattage you need, I always wondered if pumps worked similarly, and it looks like they do.

For 90% of folks building small garden ponds, this is probably useless knowledge, but it could really come in handy in specific scenarios where you have very high head height to overcome (put two or more pumps in series to increase their lifting capacities) or high flow needs (put them in parallel to get more water out the end of your pipe).

Really high flow and high head pumps seem to be very expensive and incredibly power hungry. Using this knowledge, you can use two or more pumps that, on their own, wouldn't get the job done but when combined together can do it more efficiently than one monster pump.

 

[combatwombat]

manipulate circuits to get whatever amperage or wattage voltage you need

 

[JRS]

Interesting, thanks for the link.

 

[combatwombat]

Here's an example of this concept in action when running multiple pumps in parallel. I pulled this chart (see below) from a series of pumps on The Pond Guy store.

The 2100gph pump uses 86 watts of energy. The 7800gph uses 607 watts. How many small pumps would it take to get the same flow as the big one? 7800 / 2100 = 3.7. So, we buy 4 small pumps instead. Now we're doing 8400gph for 86 watts x 4 = 344 watts. That's 10% more flow for 57% of the energy.

What does that look like for your power bill? Average cost of a kwh in the US is $0.132. In one month, the big pump will cost $58 to run. The 4 small pumps will cost $33. Difference of $25/month or $300/year or $1500 lifetime energy savings if you expect the pump to last 5 years. Savings gets better and better the longer they last.

Imagine if you lived in Hawaii where the electric cost is 3x national average.

There's another benefit: redundancy. If you run your whole pond system on one big pump and that pump dies, you instantly go from 7800gph to 0gph instantly. Big problem! If you run it on 4 small pumps and one dies... you lose 25% of your flow and hardly notice. Maybe think about replacing the dead one after you get back from your next vacation.

Caveat: You will see in the image below that the big pump works at over 2x the head pressure of the small one, so if you were planning to buy from this series of pumps, this example would only work if you have very low total dynamic head (ie. low or no waterfall and short runs of large pipe).

 

[GBBUDD]

Not my idea of a task worth the effort. i believe you will shorten the lives of the pumps. even iff the same pump in time one will start to slow while the other may not at all. I have been involved in multiple projects from hospitals hotels schools and residence and i have never see a call for in series pumps on the same lines. Even city water lines have pumping stations and if i am not mistaken even those have holding tanks. i do know water dept guys now you got me thinking and will ask.

 

[combatwombat]

I th

Not my idea of a task worth the effort. i believe you will shorten the lives of the pumps. even iff the same pump in time one will start to slow while the other may not at all. I have been involved in multiple projects from hospitals hotels schools and residence and i have never see a call for in series pumps on the same lines. Even city water lines have pumping stations and if i am not mistaken even those have holding tanks. i do know water dept guys now you got me thinking and will ask.

I think you will see this strategy employed more in municipal water / storm water management / and industrial systems where the size of pump needed would be prohibitively expensive and/or pumps need to be able to be serviced without shutting down production.

 

[scracing]

Good information

 

[\-o-O-o-/ Max Thrust]

good information. Thanks. I will probably use this when I expand my pond.

 

[kant]

Very interesting. I have two pumps in parallel, one electric and one solar. I had the feeling that when the two worked together they gave more flow than when they worked individually. This is demonstrated with calculations.

 

[tarry]

Works well if you have very low head. But if you have 10' of head, look what happens:

607 watts pushes 5725 gph --> 1 pump pushes 5725 gph with 607 watts
86 watts pushes 1100 gph --> 4 pumps push 4400 gph with 344 watts
Add a 5th pump: --> 5 pumps push 5500 gph with 430 watts

So you are still doing better -- 96% of the flow for 71% of the power -- but I bet if you head gets a little higher you'll end up in a worse situation.
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I've been thinking about this because the newer DC pumps are so much more efficient than AC pumps, but they run at much lower rates. I currently run a 10,000 GPH pump (Anjon MS-10000) through ~60' of 3" diameter pipe with only 1 right angle turn, so I figure around 5' head loss (this pumps into a bog so there's only a couple inches of actual lift). That's 780 watts for 9800 GPH. $530.

Now consider a Simplicity DC-3200. Rated at 3200 GPH and just 85 watts, $175 each. 3 pumps gives a nominal 9600 GPH at 255 watts, for $525. Sounds like a huge win, right? But these pumps have awful flow/pressure characteristics. At 5' of head, flow is only 2100 GPH. Now I need 4.5 pumps to match the Anjon -- 9450 GPH, 382 watts, $800. I recoup the extra capital cost in 10 months, but I'd need lots of extra plumbing and I'd need to figure out where to put them.

Worse, if the head is actually 10', the Anjon drops to a respectable 8800 GPH, while the DC pumps drop to 1200 GPH -- now I need SEVEN pumps to equal the Anjon, and I burn 595 watts - it will take 3 years to pay off the capital cost difference.

Seems as if, until they can build DC pumps with double or triple the current outputs, I'm better off staying with a single power-hungry AC pump.