Hey there, if you’ve ever stopped to wonder what’s inside a metering pump (you know, those tiny but mighty workhorses that dose exact amounts of chemicals for water treatment, pharma, or even backyard pool maintenance), you’re in the right spot. As a metering pump supplier who’s been on the ground helping folks pick the right gear for over a decade, I get asked this question all the time. People assume it’s just a hunk of metal and a seal, but nope—every part of a metering pump is built for a specific job, and picking the wrong material can turn a simple dose into a huge mess (we’ve all heard the horror stories of a pump failing mid-batch because of a cheap part, right?). Today, we’re breaking down exactly what these pumps are made of, no stuffy jargon, just real talk from someone who’s seen it all. Metering Pump
First off, let’s start with the most obvious part that touches the fluid: the wet-end. That’s the section that holds the chemical you’re dosing, and it’s make-or-break because chemicals can be finicky. I’ve had a client dump $10k worth of raw material because they used a pump with a plastic wet-end that dissolved in a harsh acid. Not fun. So what materials do we actually use here? Let’s run through the big ones, and why we pick each.
First up, PVC. Yeah, you’ve heard of PVC—it’s that clear or gray plastic used in plumbing. Wait, no, not just plumbing-grade PVC. For metering pumps, we use what’s called CPVC sometimes, or high-grade PVC that’s stabilized for chemical resistance. It’s cheap, lightweight, and works great for mild stuff like chlorine, dilute acids, and even some household chemicals. But here’s the catch: it’s not for everything. If you’re dosing hot chemicals (anything over 140°F) or strong solvents, PVC will start to warp or leach weird stuff into your fluid. I had a wastewater client try PVC for a 120°F bleach solution a few years back—within two weeks, the wet-end had swollen so bad the flow rate was off by 30%. That’s when they switched to PVDF, and haven’t had an issue since.
Speaking of PVDF, that’s a big one for us. PVDF (polyvinylidene fluoride) is a fluoropolymer, like Teflon, but way more durable for heavy industrial use. It’s acid-resistant to almost every common industrial chemical, works in temps up to 300°F, and doesn’t leach even when you’re dosing super pure stuff—perfect for pharma or semiconductor manufacturing where contamination is a death sentence. We use PVDF for like 40% of our metering pumps now, mostly for clients in water treatment and specialty chemicals. Yeah, it’s a bit pricier than PVC, but the peace of mind is worth it. One food and beverage client we work with uses PVDF pumps for dosing food-grade citric acid, and they’ve had zero contamination issues in five years. That’s the stuff you can’t put a price on.
Then there’s stainless steel. Wait, not your regular kitchen stainless—we use 304 and 316 grade stainless steel for metering pumps. 304 is the standard, works for mild acids, bases, and even saltwater (to a point). But 316 is the heavy hitter—has molybdenum added, so it resists corrosion from chlorides, strong acids, and even things like sulfuric acid at medium concentrations. We save stainless steel for jobs where plastic can’t cut it, like dosing hot sulfuric acid for metal plating, or brine for desalination plants. The downside? It’s heavy, it can rust if you don’t pick the right grade (we’ve seen 304 fail in high-chlorine environments), and it’s more prone to scratching, which can lead to leaks over time. But when you need it, you need it. I always tell clients: if your chemical is anything stronger than 5% hydrochloric acid, skip the plastic and go for 316 stainless.
Oh, and let’s not skip glass. Wait, glass? For metering pumps? Yeah, specialty glass (like borosilicate or even quartz glass) is used for super corrosive chemicals, like hydrofluoric acid, that even PVDF can’t handle. It’s inert, doesn’t react with almost anything, and lets you actually see the fluid moving, which is a huge plus for small-batch pharma or lab applications. The downside? It’s fragile—so you only use glass for low-pressure, low-volume pumps, not for heavy industrial jobs where it might get jostled around. We’ve got a few lab clients who swear by their glass wet-ends for testing new chemical formulations, since they can spot a bubble or a reaction instantly.
Now, moving beyond the wet-end, let’s talk about the other parts that keep the pump running. The diaphragm, for example—this is the part that actually moves to push the fluid through, right? It’s the heart of a metering pump, and most of the failures we see are diaphragm-related. What are those made of? Again, depends on the job. EPDM is common for mild chemicals, seals well, and is cheap. We use EPDM for a lot of pool and mild water treatment applications. But for harsh stuff, we use PTFE (Teflon) diaphragms. PTFE is non-reactive, works in almost every chemical, and holds up way longer than rubber. The only downside? It’s more expensive, and it’s not as flexible as rubber, so it might not be the best for low-flow, high-cycle applications. We’ve got a food processing client that uses PTFE diaphragms for dosing vinegar and other acidic food ingredients, and they last 2x longer than the old EPDM ones they were using.
Then there’s the pump head, the part that holds the diaphragm and connects the wet-end to the drive. Most of the time, the pump head matches the wet-end material—so PVC heads with PVC wet-ends, stainless heads with stainless wet-ends. But some pumps have a lining inside the pump head if the main material isn’t chemical-resistant. Like, we’ve had aluminum pump heads lined with PVDF for clients who need aluminum’s strength but PVDF’s chemical resistance. It’s a middle ground, works great for medium-duty jobs where cost is a factor.
Seals and O-rings—these tiny parts get overlooked, but they’re the reason pumps don’t leak. What are those made of? Same as the diaphragms, mostly EPDM, PTFE, or Viton (which is another brand of fluoropolymer, super chemical-resistant). We always tell clients: if you’re switching to a new chemical, never forget to check the O-ring material. Last year, a paint manufacturing client bought a pump from a supplier that used cheap EPDM O-rings for a strong solvent they were dosing. Within a month, the O-rings crumbled, and they had 50 gallons of solvent leaking all over their floor. Total disaster—cost them way more than saving a few bucks on parts. That’s why we never skimp on seals, even if it means a small upcharge.
The drive mechanism, too—wait, that’s the part that actually powers the pump, right? The motor and the crankshaft? Most of those parts are made of steel, but they’re usually coated or treated to resist corrosion. For example, we use zinc-plated steel for the drive parts in most of our standard pumps, and for heavy industrial pumps, we use powder-coated steel or even stainless steel drive parts to handle harsh factory environments. I always tell clients to ask about the drive material if their pump is going to be outside or in a damp area—regular steel will rust if you don’t coat it right.
Now, let’s get real for a sec: there’s no “one-size-fits-all” material for metering pumps. I see so many clients try to save money by buying the cheapest pump they can find, only to end up replacing it every six months, or worse, dealing with a chemical leak. Let’s take two examples: if you’re dosing dilute chlorine for a small swimming pool, a PVC pump will work perfectly, it’s cheap, and it’ll last years. But if you’re dosing hot, concentrated sulfuric acid for a metal plating shop, PVC will dissolve, and you need 316 stainless. If you’re dosing a super pure chemical for a vaccine, you can’t have any leaching, so PVDF or glass is non-negotiable. That’s why as a supplier, we don’t just sell parts—we ask questions: what’s the chemical? What’s the temperature? What’s the pressure? Do you need it for food, pharma, or industrial? Only then do we recommend the right materials, because we’ve seen what happens when you guess.
Wait, I should also mention some newer materials we’ve been testing lately, just to keep things fresh. Like, there’s a high-performance polymer called PEEK (polyether ether ketone) that’s gaining traction for some applications. It’s super strong, heat-resistant, and works with a lot of chemicals, cheaper than PVDF but more expensive than PVC. We’ve been using it for a few clients doing high-temperature water treatment, and so far, it’s holding up way better than expected. Another one is ceramic—for really high-wear applications, like dosing abrasive slurries (like mining materials or paint pigments). Ceramic is way harder than metal or plastic, so it doesn’t scratch or wear down even when you’re pumping gritty stuff. We’ve had a mining client test a ceramic diaphragm pump for dosing iron ore slurry, and it’s lasted three times longer than their old stainless steel pump. Cool stuff, right?
But here’s the thing I want you to take away: when it comes to metering pump materials, it’s all about matching the material to your specific application, not just picking the cheapest or shiniest option. We’ve made our fair share of mistakes over the years—like selling a PVC pump to a client who was dosing 10% hydrochloric acid, and it failed in three days. We learned our lesson: now we do a full material check with every client before we even quote a pump. No exceptions.
If you’re not sure what material you need, or you’re tired of dealing with pumps that fail, hit us up to chat. We can walk you through your specific application, answer any questions you have about materials, and help you pick a metering pump that’ll last, no leaks, no headaches. Don’t waste money on cheap parts that’ll cost you more in the long run—let’s get it right the first time.
Progressive Cavity Pump REFERENCES
- Metering Pump Material Compatibility Guide, National Association of Water Companies
- Chemical Resistance of Thermoplastics, Society of Plastics Engineers
- 316 Stainless Steel Corrosion Resistance for Industrial Pumps, American Society of Mechanical Engineers
- High-Performance Polymers for Fluid Handling, International Society of Pharmaceutical Engineers
DEPAMU (Hangzhou) Pumps Technology Co., Ltd.
DEPAMU (Hangzhou) Pumps Technology Co., Ltd. is one of the leading metering pump manufacturers and suppliers in China, with professional factory we are able to produce Chinese best metering pump at both low price and good quality. If you are looking for Germany technology or famous brand metering pump, please feel free to contact us.
Address: No. 658, 20th Street, Hangzhou Economic & Technological Development Zone, Hangzhou City, Zhejiang Province, China
E-mail: international@depamu.com
WebSite: https://www.depamupumps.com/
