#1.7 Mixing Valve Sizing: Why Pipe Size is Misleading?

We’re diving deep into the practical mechanics of thermostatic and digital mixing valves, featuring the Caleffi 521 Series and the 520 AngleMix™. Moving beyond the spec sheet, we break down how these valves actually behave in the field, and why sizing design flow rather than pipe size is critical for performance. 

What we cover in this session:

• The Standards Playbook: Why distinguishing between ASSE 1017 (point-of-distribution) and ASSE 1070 (point-of-use) is the only way to ensure true anti-scald protection.
• The 1017-before-1070 Rule: How to avoid the 120°F hard-stop trap.
• The Oversizing Epidemic: Why sizing by pipe diameter instead of Cv leads to "hunting", and how to use ultrasonic flow meters to get the math right.
• Digital vs. Thermostatic: Navigating minimum flow requirements and the tighter temperature bands of electronic controls.
• The Real-World Fix: Why you should adjust your settings based on the farthest fixture’s thermometer, not the valve’s dial.

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Transcript

Speaker 1 0:01

Welcome to the Ask Caleffi podcast coming at you live from the lab.

Speaker 3 0:06

Guys, what do we got going on? Plumbing, hydronics, expert insights, and a few stories from the trenches. Whether you're on the job or just along for the ride, we've got you covered.

Speaker 1 0:22

Well, today we're going to talk about mixing valves, thermostatic mixing valves, um, and electronic mixing valves. I mean, we do a pretty good job of bringing a lot of different offerings to the table. Um, you know, from 1017 to 1070 valves, there's quite a few options, and we're just gonna have a conversation about them, you know, where they go, how they work, and and uh hopefully that helps everybody else uh understand what goes on inside of one of them. So Matt, you got one right there in front of you. It's uh an ASSE 1017 valve. Correct.

Speaker 1:00

Yeah, this is our our 521 series, um, kind of our standard workhorse, especially for you know residential applications, small like commercial applications. Um this would be installed at you know the point of um mix distribution. Point of distribution, I'm sorry, thank you. Um and you know, you can temper 10, 12 GPM um down to you know whatever you you want to set it down to.

Speaker 1 1:30

Yeah. Um like you said, it's it's a very legacy product for us. It's a you know, the cross-shaped uh mixing valve. Um is that kind of the first thermostatic that Cleppy brought to market? It is the very first in our market, yeah, in the North American market. So um, you know, you hit the nail on the head with it you're we're able to handle up to about 12 GPM at a 20 PSI drop, right? Correct, yeah. So if that's acceptable, then this is the right valve for you. I mean, application is is always key. The more information you can give us about the application you're working through or working with, um, you'd be able to uh we'll be able to help you pick the right valve.

Speaker 2:11

For sure. Yeah, that's that information is critical when selecting your mixing valve. Um, but I mean for typical single-family residents, um, this is gonna be more than enough valve.

ASSE 1017 Vs 1070 Explained

Speaker 1 2:22

Yeah. Definitely. And to kind of clarify things, like we threw out an ASSE standard, right? ASSE. What can you tell us about ASSE?

Speaker 2:33

Right. So ASSE stands for the American Society of Sanitary Engineers, and they are kind of a governing body. Um, they make all kinds of standards. One standard, ASSE 1017, governs point of distribution mixing valves. Um, another one pertinent to mixing valves is ASSE 1070, and that's point of use. So that's gonna be like a sink mixer, Roman tub mixer, something that's just controlling a single or one or two fixtures. Um, and those those have different um limitations to them. Like a 1070 valve, you cannot set above 120 degrees Fahrenheit. That's the cutoff. Um, they require inlet check valves, um, where a 1017 could have that. Um, it can be you know turned up to I believe it's 150 degrees. Yep. Um but it and then there's there's also skull protection as is a must-have in in 1070. So in the event that you lose pressure on the hot or the cold, it's gonna shut down flow completely, basically.

Speaker 1 3:35

Yeah, and that's that's what that cartridge is designed to do. So if we were to take and look at that cutaway that you had in hand there, um that cartridge is is the limiter, right? Actually, the knob is the limiter of how far the cartridge can open and close. So that's how we're making that adjustment for more hot or less hot exact water going in to mix.

Speaker 3:57

Yep. Yeah, this the spring tension is is governed by you know what setting you have on this knob, and then that that tension is gonna restrict that shutter up and down, mixing more more or less hot or cold as as needed.

Speaker 2 4:11

Yeah, that thermostatic element's gonna react based on that outlet temperature to drive those shutters. Exactly. Yep, yep, okay right there.

Speaker 1 4:18

Yeah, absolutely. And I bet Ryan, you take a ton of calls. I know I did on these mixing valves all the time.

Speaker 4 4:25

Yeah, definitely. Everybody's you know installing stuff different and got questions or just not working properly. Um, yeah, they're great for plumbing and uh hydronic as well.

Placement Rules And Real-World Adjustments

Speaker 1 4:37

Yeah, I mean we used it a ton in the in the field. Yeah, it might not have been this particular model, but it something similar where we're trying to bring the the delivery temperature of the water going into we'll say a concrete floor. Um we're trying to bring that down so we don't crack the concrete, right? For low temperature radiant application, exactly. So it it's pretty handy to have that way also. Um going back to the 1070 valve, I think people want to know, well, where should this go? We kind of explained it already, but I think the easiest way our our our buddy Kevin over here, the the engineer, he explained it to us a long time ago that you know, think about it numerically. The number 1017 always goes before 1070. So 1017 right at your water heater or your heat plant, whatever at your source. And 1070, 1069, 1071, 1069, 1071 are different standards, but they are an anti-scald standard, right? Right, right. They still have that application, those go further out in the system. So 1017s always go first, 1070s later. I don't I don't know how many calls you've gotten about somebody putting a 1070 valve right off a water heater. Dan and I used to get them all the time. Sure, yep. And you go, why did you put that there? Because it is hard stop at 120. That cartridge is starting to close off once it gets any higher.

Speaker 4 6:06

Yep, they can't get anything over 120 out of the mixed outlet of it. And yeah, um, like you said, stops.

Speaker 1 6:13

It's all about application. Yep, it is exactly. And you get people got to remember too, there's losses in the system, right? So just because you set the valve at 120 doesn't mean you're getting 120 all the way out to you know your second floor bathroom. Yeah, you got a heat loss that whole way up, right? Chances are that piping's not insulated. Um, you're just not getting enough flow that that far because of all the pipe in the elbows, the friction loss inside. So it's you might have to tweak that a little bit. You might have to adjust it just because you think you need 120 out of that valve doesn't mean you're getting 120 into the faucet. Right. So it takes some adjusting. And I always tell people, look, use your favorite thermometer, your most accurate thermometer out of the bag, even if it's the meat thermometer you use for the drill. Yeah, right. You know, that'll work and uh and go to that farthest faucet and turn it on and let it run for a few minutes, see what you got. Right. And you go, well, you know, we're only getting 113 113 uh degrees at this. This isn't acceptable. Someone's gonna complain. So we go down and we adjust that valve up.

Speaker 2 7:16

Well, and your adjustment setting might be different in different applications, and it's gonna depend on what your source water temperature is coming to that valve. I mean, if you're in an application where you're 130 degree water coming to the valve, you may have to set to a higher number on the adjustment range to get 120 out than you would if you're 150 degree entering water temperature. Exactly. You know, and I think that's a key. And how many times have you taken that call, Ryan, where someone has a mixing valve and they're like, it's it's not delivering 120 degree water? Well, maybe the water heater's still coming up to internal temperature, or maybe the water heater source temperature is not set high enough. Right, because it's always gonna be mixing.

Speaker 4 7:57

Yeah, you know.

Speaker 1 7:58

Yep. Yeah, you so you have a differential. Every valve has a differential. You just have to uh I hate to say it, you gotta open the pamphlet and look at it because everybody's products pretty close, but not quite. You know, one valve might be 20 degrees, another one might be 17. Yeah.

Angle Mixing Valves And Recirc Creep

Speaker 2 8:15

So you know, so we we've talked about the SSE, you know, 1070 and 1017 rating and the valves we have. Uh, another product to keep in mind that Clefy has is our angle mix, our 520 series angle mix. Um, what's really nice about this valve is that you know the hot inlet and the mixed outlet are in a direct line with each other. So you know, if you're retrofitting this on top of a tank, that hot outlet coming out of the tank is coming into the hot inlet on the mixing valve. The mixed outlet going to back to the building is coming directly out above that. Um, and then the cold comes off at a 90-degree angle, so it saves you some fittings. Really quick reacting cartridge, too. So it has the ability to close hot and cold 100%. Um, and it and it's it's so good that we're able to actually get this dual listed. Yeah. So this model will fit in the two C V body, it will meet the ASSE 1017 and 1070 standard.

Speaker 9:09

Right. Yeah, that the the one that actually is dual listed has a a little bit different cap, and it's got um kind of a set screw inside there that limits that um that outlet temperature to 120, and then obviously it's got inlet check valves, um, and that again that that real quick reacting element inside there that will shut shut off in the event of uh you know runaway temperatures or uh pressure loss on on either side. Yeah.

Speaker 1 9:36

It it does a nice job of helping prevent resert creep. Um, it's one of the few valves out there that does that. I mean, to my knowledge, it's the only thermostatic that does that aside from a 1070 valve, right? Right. So it's uh it's pretty neat, pretty neat setup. But you're limited, you know, nine gallons a minute on at a 20 PSI drop with that product. Um but it I like it for the fact that it says fittings, it's just a cool looking valve and it's yeah, the design is genius.

Speaker 10:07

I mean, the first time I saw that I thought it was just brilliant, honestly. Like that mixed outlet and hot inlet right in line with each other is it makes it so easy to retrofit.

Speaker 4 10:16

Yeah, it's a nice product. And the temperature difference on there is much closer than the 521. Yeah, yeah, much tighter temperature, yeah temperature band. So you don't have to crank that tank temp up so high.

Electronic Mixing Valves And Sensors

Speaker 1 10:27

Yep. Yeah. Yes, sir. Well, the only other product that we have that would close off bubble tight in a case of research creep would be our electronic mixing valve. So that's a totally different animal, right? Yeah. Um, we're relying on a control to send voltage to an actuator that uh communicates through sensors, right? We have uh a mixed outlet sensor, and then we have a research return sensor that for basic electronic mixing purposes, it's just a monitoring sensor. It just tells us what the research's coming back. It has no play on what the valve is actually doing. The only sensor that really matters is the mixed outlet sensor.

Speaker 2 11:10

Yeah, the electronic mixing valve is really nice. It's going to meet the ASSE 1017 standard for point of distribution. Uh, more of like a multifamily uh commercial mixing valve. Uh, very high CV valve body, very high flow rates, even in the small connection sizes. Um, but we have a lot of offerings from three-quarter all the way up to three-inch flange to kind of fit any application.

Speaker 1 11:35

You said something there. High CV. High C V means high flow. Whenever we're talking a high flow valve, there's something, a little flag that comes up in the back of my head that says, okay, we get all that flow, but how is it gonna react on the bottom end on a lower flow situations? And we we all know, right? Because we've all taken the phone calls and we still do every day. Yeah. What do you want to share about that?

Speaker 4 12:07

You got to keep in mind the uh minimum flow, the flow minimum. Uh three quarter inch is 2.2 gpm. Two inch will go all the way up to almost nine gpm for a minimum flow that we always have to have 24 hours a day, seven days a week, going through that valve. Yeah, that's minimum flow requirements. Right. Yeah. And if we don't meet that, this valve will start to hunt, and it'll have a hard time keeping that set temp coming out of the mixed outlet.

Speaker 2 12:41

100%. Yeah, but I mean those valves have really high design flow rates as well. So, I mean, Ryan, you talked you talked a lot about minimum flow rates. So when you start looking at design flow rates, you know, we have a chart that recommend has recommended design flow rate at a 7.5 psi pressure drop. And that's that's really what you need to consider when you're sizing the valve. Um, not pipe sizing. We get that a lot where you'll you'll walk into a job site that has a two-inch thermostatic mixing valve. You know, take a look at the requirements for that building and the design flow rates of our electronic mixing valve because you're not going to put a two-inch back into that application. You know, you you want to you want to really look at the design and size that properly.

Speaker 13:24

Right. When you see a pipe size, two valve size, one to one, like a two-inch valve on a two-inch line, almost every single time that is going to be oversized. Yeah. It's it's not uncommon to have one to even two, sometimes even three pipe size smaller valve than the actual pipe size that it's serving.

Speaker 2 13:42

Yeah, and because of that, you can see temperature instabilities or or um hunting in that control at lower flow rates because that valve is so greatly oversized. Exactly.

Speaker 1 13:54

Yeah, we've seen it plenty of times. Uh most of it is, you know, an engineer expects one thing. We get a phone call from the guy on the job, it's usually after the product's installed. Hey, how did you come to that flow rate? I mean, they used the old Hunter's curve numbers, right? Right. And how grossly oversized were those numbers back in the day, even still.

Speaker 2 14:15

I mean, I I look at an application, a tech call I took one time. You know, it was uh Harris Lawn in Tennessee where they took out an inch and a half thermostatic mixing valve and they put an inch and a half Legio mix in. And when we actually looked at the requirements of that building, it was like maximum that even the tankless water heaters could put out was 28 gallons per minute. It's like, okay, so that you're sized with a design flow rate of a valve that's three times what the water heaters can even produce. Right. So that's not applied right. I think we put a three-quarter inch back in.

Speaker 1 14:50

Yeah. And it's not uncommon to see something that looks so silly, you know, giant piping, tiny little valve. Um but the thermostatic valve was probably applied right.

Speaker 2 15:00

Yeah.

Field Story And Measuring Actual Flow

Speaker 1 15:00

Right because the CV values. Right. I just was in Michigan um looking at a hotel job with a plumber, um, three-inch pipe. The guy calls and says, Hey, I think I need a three-inch valve. Let's go take a look at that job. We're not that far. Go in there, the tank, I kid you not, is 12 feet tall in this giant mechanical room, 120-room hotel. It's a high-rise hotel, so they're boosting and they got all sorts of things going on there. And uh walk into the mechanical room and see this behemoth of a tank. It's being fed with four-inch and comes out three inch. Said, what what made you decide that you needed a valve that could flow over 500 gallons a minute? He just his his eyes just about jumped out of his skull. How much? Yeah. Oh, I said, what do you have for research? Well, I got a two-inch. Cool. You have a two-inch. Do you know what it flows? Well, the pump's up there, and of course, he needed a 20-foot extension ladder to get to it. And it was way up there, and you can't read the numbers off it. So we don't know what the curve is on it. I said, you know, there are tools to help us with this, so we don't have to try and figure this all out. It's called an ultrasonic flow meter. It's a wonderful thing. It's pricey, but if you want to be able to know exactly what you got in an existing system like that, you can put the sensor on the two-inch recircline that's tied back into the cold and let it run for 10 minutes, and it'll give you a reading of what is going on there. So it might be 20 gallons a minute or whatever it is. Okay, we know what our minimum is in this existing system. We know we need a new mixing valve. We need to put a mixing valve in here. What else do we have to do to figure out what size valve we we need here? Well, you're gonna have to put the 12-foot ladder out to at least strap onto that three-inch that's coming out of this monster tank and let it run for, you know, I say a week. Yeah. Because a week you're gonna get the peaks and valleys, right? You're gonna get Mondays, usually check uh might be a check-in day for the business people. It's they've already the the weekenders have checked out. So you're gonna have, you know, a valley down, and then it's gonna come back up towards the weekend. And if you get the two days of the weekend, the busiest days, you're gonna get a report. It'll actually give you a report, and we can go through that report with you and go, you know, we didn't see a flow higher than 150 gallons a minute. You don't need a three-inch. Right. Maybe you can get by with a pair of inch and a halves or inch and a quarters or something like that. It's good to run two smaller valves in parallel for redundancy just in case something happens. Um, but it's not uncommon where they'll just size one valve and be fine. Right, right.

Speaker 4 17:44

Like you said, that auto so ultrasonic uh sensor. Yep, flow meter. You know, it's it's pricey, but it's gonna save you so much time and headache on the back end.

Speaker 2 17:56

You get it right the first time. Yeah, you really know what you're sizing for and designing for. Yeah. So take that with a grain of salt. Well, I think when it comes down to it, I mean, it depend it. Doesn't matter what your application is, we're gonna have a product that's gonna fit that.

Speaker 1 18:14

Definitely. Definitely. And we always have someone here to answer the phone and help you figure out what you need.

Speaker 3 18:22

Well, that's a wrap for this episode. Got questions or stories to share? We'd love to hear from you. Reach out and let's keep this conversation going. Don't forget to subscribe and leave a review wherever you're listening. Until next time, stay curious and keep your systems running smoothly.