Advanced plumbing: pumps in series! Does anyone have experience?

[UncommonSense]

I’ve been mulling over an interesting idea recently, basically to avoid buying more new lift pumps…

So, let’s talk pump plumbing!

When we see two or more pumps feeding one return, manifold, or piece of equipment; this is typically in a parallel configuration for pump redundancy, and a nominal max flow increase.

However, I don’t really hear people in the aquarium hobby ever talking about running two pumps in series!

— this plumbing arrangement ties one impeller pump’s outlet to a second impeller pump’s inlet. This effectively combines both pumps maximum lift heights, with a minimal gain in flow rate.

This series configuration is ideal for applications which are high pressure, lower flow.

I decided to do some digging on how this concept is used in the real world for more serious commercial applications, and found some enlightening comments within engineering forums about the topic!

Primarily discussed were the issues, or lack thereof with this plumbing arrangement. however, an interesting point about potentially over-pressurizing the upstream pump’s volute/seals was brought up!

Here’s an example of a very thoughtful user’s words on bypass plumbing and phased pump starting, in context to massive external pumps for a raw water treatment facility… — as far as I’m aware, these factors are less relevant in a submersible series plumbed pump application… or, are these drawbacks still a concern in a submersible application somehow that I’m missing?

thoughts?

 

[Peace River]

Yes, it increases the head pressure but cavitation can be an issue. Iwaki or Panworld pumps provide high head pressure.

 

[UncommonSense]

Yes, it increases the head pressure but cavitation can be an issue. Iwaki or Panworld pumps provide high head pressure.

I definitely have cavitation in mind! — it seems to become more relevant when one pump is undersized and effectively functioning as an orifice at higher flow rates!

I actually have multiple of both brand’s external pumps laying around; beautiful pieces of equipment, internally…

This is moreso a curiosity for a potential application where there is no submerged bulkhead to plumb to an external pump, and it’s not my sump to drill! — hence the submersible pumps in series!

(In one of my personal systems, It would also let me test the known max head of one of my smaller Iwaki pumps using equipment I have laying around… this would tell me if gutting and drilling the sump for a submerged bulkhead is worthwhile!)

 

[Peace River]

IME, cavitation can also become an issue when one pump becomes functionally undersized due to degraded performance based on an array of reasons.

 

[UncommonSense]

IME, cavitation can also become an issue when one pump becomes functionally undersized due to degraded performance based on an array of reasons.

Wouldn’t this be more of an issue on startup, especially with external pumps in series?

I do know that there was discussion of pitching impeller vanes to throttle flow through the upstream pump on the significantly nicer pumps used in industrial applications, but this was more for flow rate control than cavitation…

The risk of over pressurizing the upstream pump’s impeller housing and seal(s) is definitely something to consider too, though it would really depend on the pumps in question…

 

[Peace River]

At start up and at failure or degraded performance. It’s an interesting experiment. Just realized it comes with challenges.

 

[Peace River]

I have learned more from stuff that didn’t work than the stuff that did exactly what it was supposed to. The problems for me come in when I assume that everything I try is going to work.

 

[UncommonSense]

I have learned more from stuff that didn’t work than the stuff that did exactly what it was supposed to. The problems for me come in when I assume that everything I try is going to work.

Aptly put, good sir!!

That’s exactly why I’m bringing up the topic to make sure there isn’t a glaring hole in my logic, then simply putting it to a real-world test!

Would anyone be interested in my results?

 

[Peace River]

It’s worth posting because even if someone doesn’t need it right now, they likely will need it in the future. There are things that I have come across on the R2R forum from years ago that have helped me find some obscure answer to one of my questions.

 

[Tangdora]

Cost is probably a simple reasoning why you don’t see this much. Brand to brand assuming they have variety it’s probably always cheaper to size up and stay with a single pump then to get two just to run in series. Plus if the main benefit is mainly head pressure. Going bigger and routing to a basement or closet is probably people’s first choice as you’re now eliminating sound. . Think this ever only become consideration when physical obstructions come into play where two smaller at different sport be have to do. Plus that would be some ugly piping imo if trying to place close together given centrifugal pumps create natural 90s.