Hey there, I’m Jake, and I’ve been selling horizontal multistage pumps for about 7 years now—long enough to know that when a customer shoots me a question like, “Can I hook two of these bad boys up in series?” it’s never a random thought. Most of the time, they’re staring at a project where one pump just won’t cut it: maybe the piping system needs a way higher head than a single unit can push, or they had a pump fail and are wondering if swapping in another will get them back up and running fast without splurging on a whole new system. Let’s cut the jargon and get real about this, because I’ve seen this play out in factories, water treatment plants, even large residential well setups more times than I can count. Horizontal Multistage Pump
First, let’s do a quick refresh on what a horizontal multistage pump actually is, because I get that not everyone speaks pump geek. Unlike a single-stage pump (which has one impeller pushing fluid), these have multiple impellers stacked on the same horizontal shaft—each one adds a little more pressure, right? So a 10-stage unit can push way more head (that’s the total pressure the pump creates, usually measured in feet) than a 2-stage one, even if they’re the same frame size. That’s why they’re so popular: compact, efficient, and way more versatile than most folks give ’em credit for.
Now, back to the big question: yes, you can connect two horizontal multistage pumps in series. But here’s the thing—you can’t just yank two random pumps out of storage, plumb ’em pipe-to-pipe, and flip the switch. I’ve seen a customer do that once (shoutout to that food processing plant in Ohio) and end up burning out two pumps in 48 hours. Why? Because they skipped the most critical part of series connections: matching the two pumps’ curves.
Let’s break that curve thing down real simple. Every pump has a performance curve—it’s that graph that plots flow rate (how much fluid it moves per minute, gpm or m³/hr) on the x-axis against head (pressure) on the y-axis. When you put two pumps in series, their curves add up at every flow point. So if Pump A does 100 gpm at 150 ft of head, and Pump B does the exact same at 100 gpm, together they’ll do 100 gpm at 300 ft of head. But if their curves don’t line up—say Pump A maxes out at 120 gpm at 200 ft, and Pump B only does 100 gpm at 100 ft—you’re gonna end up with a weird “kink” in the combined curve. That mismatch forces one pump to work way harder than it was designed for, or worse, to operate in a low-flow zone where cavitation happens.
Cavitation is the silent killer here, by the way. It’s when fluid pressure drops so low that little vapor bubbles form in the pump’s impeller, then collapse violently when they hit a higher pressure area. Those tiny collapses erode the impeller over time, cause weird noises, and can destroy a pump fast. When you connect mismatched pumps in series, one might end up running at a flow rate way below its best efficiency point (BEP)—that’s the sweet spot where it’s most efficient and least likely to cavitate. I’ve fixed multistage pumps where the impeller looked like it had been sandblasted, all because someone didn’t check their curves.
Another non-negotiable here: making sure both pumps are rated for the same suction pressure. Wait, why suction pressure? Because when you put pumps in series, the first pump pushes fluid into the second pump’s suction side. If that second pump isn’t built to handle the pressure coming at it from the first, it’s like trying to blow up a balloon that’s already been overinflated—it’ll burst. I had a guy call me last month panicking because his second pump was leaking out the shaft seal, and turns out he paired a low-pressure residential pump with a high-pressure industrial unit. The first pump was pushing 180 psi, and the second only handled up to 100 psi—boom, seal failure. Lesson learned: check that suction pressure rating on every unit before you hook ’em up.
Now, let’s talk about when series connections make total sense, because it’s not for every job. Let’s say you’re upgrading a water system for a new development. The existing single multistage pump only does 200 ft of head, but you need 350 ft to get water to the top of the 10-story building. If you swap that single unit for a slightly bigger pump, you might waste money on overkill when you could just add an identical pump in series, plumbed right after the first. Or maybe you have a pump that’s failing regularly because it’s operating at max head—adding one in series takes the load off each individual unit, so they run cooler, last longer. That’s the thing about series: it’s a great upgrade path, not a band-aid.
Wait, but what about parallel connections? I get why some people confuse the two. Parallel is when you hook pumps up side-by-side to double flow rate for big jobs, like a municipal water plant. Series is all about upping the head, which is exactly what you need if your problem is not enough pressure to get fluid to a distant spot or a high elevation. I always tell customers to ask themselves: do I need more flow, or more push? If it’s push, series is your guy. If it’s flow, go parallel. And for multistage pumps, since their whole design is about building head incrementally, they’re perfect for series—each impeller is already like a tiny series stage, so stacking two full units feels natural, not forced.
Let’s dive into a real example to make this concrete. Last year, a mining client reached out to me because their slurry transfer line was only getting half the head they needed to move material 2 miles away. They had two horizontal multistage pumps already, but they were different models from different brands, and someone tried to connect them a year prior with disastrous results. I sat down with their maintenance team, pulled the spec sheets, and found two identical 12-stage horizontal multistage pumps that matched the original units’ curves almost exactly. We plumbed them in series with a check valve between them (super important—no backflow! If the first pump stops, the second could push fluid backward, which would damage both), then tested the system. They went from 180 ft of head to 360 ft, hit exactly the flow rate they needed, and those pumps have been running for 11 months now without a single seal issue or impeller wear. That’s the win we’re all after.
Now, the common mistakes I see customers making, and how to avoid them. First, skipping the curve match step. Don’t just take my word for it—always cross-reference the pump performance curves. Most manufacturers post these online, or you can hit me up and I’ll send ’em over. Second, forgetting the check valve between the two pumps. Backflow is a real risk, especially if the power flickers. A check valve lets fluid go forward only, so if one pump shuts off, the other doesn’t have to work against reverse flow. Third, not accounting for system friction loss. Wait, what’s that? Every pipe, elbow, valve, and filter adds resistance to fluid flow. When you calculate the total head your system needs, you can’t just go by static elevation. You have to add that friction loss. If you don’t, you might size your series connection wrong, and end up with either too much head (wasting energy) or too little (back to square one).
Another thing I get asked all the time: can you mix different horizontal multistage pumps? Like, a 5-stage and a 8-stage? Technically, yes, but I’d only recommend it in a pinch, and only if their curves align at your specific operating flow. But why risk it? Identical units are cheaper long-term, easier to service (you can swap parts between them), and less likely to cause issues. I once had a customer mix a 6-stage and a 9-stage to save a few bucks, and within 6 months, the 9-stage’s impeller was worn out because it was running at a flow that was too low for its curve. Replacing that single impeller cost way more than just buying an identical second pump would have.
What about maintenance when you run pumps in series? It’s not that different from a single unit, but you have a few extra checks. Every month, make sure the pressure gauges on both pumps are reading correctly. If the first pump’s discharge pressure is way higher than the second’s suction, that’s a red flag—means they’re not matching. Also, check that shaft seals on both units are staying tight. The first pump takes the brunt of the pressure, so its seals might wear a little faster than the second’s, but if both are maintained regularly, you won’t have issues. Oh, and keep an eye on vibration—if either pump is vibrating more than usual, that’s probably a misalignment from bad plumbing, not the series connection itself.
Wait, let’s address the elephant in the room: is connecting pumps in series efficient? Sometimes, yes, sometimes no. If you match the curves and size them right, it’s almost as efficient as a single larger pump. But if you mismatch them, you’ll lose a lot of energy because one pump is working harder than it needs to. That’s why so many industrial clients swear by identical series connections—it’s not just about pressure, it’s about saving on electricity bills. I’ve had a textile plant tell me their power usage dropped 12% after they replaced their mismatched series pumps with identical ones. That’s a huge win for their bottom line.
Now, what about residential use? A lot of people don’t realize horizontal multistage pumps aren’t just for factories. They’re used in large well systems, whole-house water pressure boosters, even pool heating systems. Can you put two in series for a big custom home with a pool, a 5-car garage, and a guest house on a hill? Absolutely. I helped a guy in Colorado do that for his 8,000 sq ft home last year. His original pump only pushed 120 ft of head, which wasn’t enough to get water to the guest house. We plumbed two identical 4-stage pumps in series, added a pressure tank to smooth out flow, and now he has consistent pressure everywhere, even when the sprinklers are all running. No more waiting for water to hit the shower at the top of the house—game changer.
But here’s a caveat for residential folks: don’t try to do this yourself if you don’t know pump basics. I’ve seen guys try to plumb their own series connection with parts from the hardware store, and they end up with leaks or burned-out pumps. It’s better to either work with a pump pro (that’s me, by the way) or make sure you have a clear curve match and check valve before you start.
So to wrap this up: yes, a horizontal multistage pump can absolutely be connected in series, but only if you follow the rules. Match the performance curves, check suction pressure ratings, add a check valve between them, calculate total system head correctly, and use identical units whenever possible. Skip those steps, and you’re looking at expensive repairs and downtime. Do them right, and you’ve got a reliable, efficient way to get the extra pressure your project needs without breaking the bank on a whole new pump system.
If you’re sitting there right now thinking, “Hey, that’s exactly my problem—my pump’s not enough head, and I’m not sure what to do next,” hit me up. I don’t do pushy sales stuff, I just give honest advice because I’ve been in this game too long to see people waste money. I’ll send you the curve specs, help you figure out if two of our horizontal multistage pumps will work for your job, or even troubleshoot if you already tried a series connection and it’s acting wonky. No pressure, just real talk about pumps.
Vertical Multistage Pump References:
- Hydraulic Institute. (2021). Pump Application Handbook: Series and Parallel Operation of Centrifugal Pumps. Hydraulic Institute.
- Karassik, I. J., Messina, J. P., Cooper, P., & Heald, C. C. (2014). Pump Handbook (4th ed.). McGraw-Hill Education.
- American Water Works Association. (2019). Water Treatment Pumping Station Design Guide. American Water Works Association.
- Fluid Handling Society. (2022). Horizontal Multistage Pump Application and Installation Best Practices. Fluid Handling Society.
Xiaofeng Machinery Technology Co., Ltd.
As one of the most professional horizontal multistage pump manufacturers and suppliers in China, we also support custom service. Please feel free to wholesale advanced horizontal multistage pump made in China here from our factory. Quality products and reasonable price are available.
Address: No.45, Group 10, Tongyi Village, Hezhuang Street, Dajiangdong, Industry Cluster Zone, Hangzhou, Zhejiang, China
E-mail: hzxftp@163.com
WebSite: https://www.hzxfmt.com/
