How to Calculate Total Dynamic Head

Finding the right pump for a water feature can be a challenge, and the stakes are high. The right pump, delivering the right flow at the right head height, while at its Best Efficiency Range, will last and last. Specifying the wrong pump or plumbing can damage the pump, increase operating costs, shorten pump life and lead to pump failure, perhaps even a fish kill if the water feature happens to be a fish pond.

In order to properly size the pump for any water feature, you’ll need to know both components of the work it has to do, the flow and the pressure. The flow is the volume of water it can push in a given time, measured in gallons per hour (GPH). The pressure is the force required to push that flow through plumbing and up to the top of the water feature. We measure pressure in ‘feet of Head”, because it’s easy to visualize. A waterfall four feet high requires the flow be delivered at 4 feet of “Vertical Head”, plus the extra work required to push that flow through the plumbing, the “Friction Head”. The total pressure required is the “Total Dynamic Head” (TDH) of your water feature. Once you know the GPH and the TDH, you can plug them into the Comprehensive Pump Chart (Chart C) to find the right pump.

Follow the steps below to calculate TDH and find the perfect pump for your water feature.

Find the GPH needed to achieve the look you want

determine friction loss

FIND TUBING SIZE & FRICTION

Find the dark blue cell in the row that corresponds with the Recommended Flow (GPH) in the chart below. The column indicates the recommended tubing size and the number in the cell is the Friction Loss in every foot of tubing. Keep Friction Loss low for greatest flow.

To find the Friction Loss of existing systems, estimate the flow through the actual tubing size used.

Chart A


ADD FRICTION IN FITTINGS

Add the equivalent lengths of all the fittings in the system from the chart below.

CALCULATE FRICTION HEAD

Multiply the Equivalent Tubing Length in feet by the Friction Loss in the dark blue cell from CHART A to find the Friction Head of the system.

FIND THE TOTAL DYNAMIC HEAD

Add the Friction Head in Feet to the Vertical Head of the system. Vertical Head is the height in feet from the surface of the water the pump will be TDH sitting in, to the highest point the water is pumped to.

CHOOSE YOUR TIDALWAVE PUMP

Find the TDH at the top of CHART C, then find the pumps below that provide at least the Recommended Flow. Grey colored cells indicate that the TDH is outside the pump’s operating range and the pump will likely not last in this application. The light blue cells indicate the pump is operating within its operating range. Dark blue means the TDH is in the pump’s Best Efficiency Range, where the pump will run best and longest. If the chart gives you a choice of more than one pump, check for the type that best fits your application from the list below, then check for the lowest wattage, to save on operating costs.

  • For Low Head, Low Volume applications, use Magnetic Drive Pumps (MD Series)
  • For Low Head, Very High Volume applications, use Axial Pumps (L-Series) with 3″ or larger tubing
  • For Medium Head, Medium Volume, use Asynchronous Pumps (TT-Series)
  • For High Head, High Volume Applications, use Direct Drive Pumps (A-Series)
  • For Solids and Dirty Water applications, use Direct Drive Solids Handling Pumps (PAF and SH-Series)

Chart C

To learn more on how to Calculate Total Dynamic Head, watch the How-To video on our YouTube channel, AWGtv.

Tools That Don’t Suck – The Ryobi ES1500

As water feature installers, my sons and I are used to hard, dirty, sometimes dangerous work. We enjoy what we do, whether it’s digging ponds, plumbing pumps, rolling boulders or tweaking waterfalls, but we also value anything that helps make the work easier or more fun. We’re always looking for tools, apps or gadgets that save time & effort, eliminate stress, add to our comfort on the job or are just fun to use. Often a buddy will turn us on to one. I’d like to return the favor by passing our favorite Tools That Don’t Suck along to you.

Handy Phone Tool

So, as you might expect, I often get asked to recommend a particular pump for a contractor’s project. The steps are simple and easy (not the same thing.) There are four simple steps to finding the right pump:

  • determine the required flow
  • choose the right size pipe
  • add friction head to vertical head height
  • go to the charts to find a pump that delivers the right flow at the right head

The steps are easy. Multiply the flow per foot by the width of the waterfall, in feet. Pick the right size pipe by finding the flow on a chart. Add up plumbing length. Multiply the length by a decimal. Add that result to the actual vertical height of the waterfall to find the Total Dynamic Head (TDH) – and there’s the problem.

It turns out that most people overestimate the actual height of the water feature they’re planning on building. By a considerable amount. It’s particularly hard for anyone to estimate true vertical height on a slope, where many of our potential projects are situated.

Why does that matter? Well, you need to know the true vertical height of the water feature to find the actual load the pump will be under. Knowing the true workload not only lets you pick a pump that will thrive under those conditions, you can also cut costs by using very efficient low head pumps…IF you correctly estimate the vertical head height.

The Ryobi ES1500

Photo credit: www.ryobitools.com

I have come to appreciate the Ryobi ES1500, a little gadget that takes the guesswork out of measuring height. It fits on any phone with a headphone jack. (Sorry, you need to have the jack.) I found mine at a tool store under a banner advertising Ryobi Phoneworks. For $15, I figured I didn’t have much to lose. I paid willingly, if a little dubiously, and downloaded the free app.

The “Laser Pointer/Transfer Level” plugs into the standard headphone jack on my Android phone and shoots a bright red laser beam on command. The app has a couple of level functions, including a bubble level. The easiest to use is a red dotted line with the numeric value of degrees the unit is tilted displayed right next to the line. Once the phone is level, at 0 degrees, the beam coming out is pretty level too. The accuracy of the unit isn’t stellar, but it’s close enough. It’s just bright enough to be seen in the shade during the day. I do most of my estimates after work, and it’s really visible as the light falls.

I’ve gotten pretty adept at holding the phone level, at head height, while standing where the pond will go. I note of where the roughly five-foot-high laser beam hits on a tree or a slope near the waterfall-to-be. For larger distances, I’ll repeat the process, moving to where the beam struck the ground, until I’ve worked my way upslope, five vertical feet at a time.

I will admit it’s a bit crude, but it works well enough to get a pretty accurate vertical height for the Total Dynamic Head calculations.

The Ryobi ES1600

So, as I’m finishing up writing this, I look up the Ryobi ES1500 to find there’s a new version, the ES1600, that sounds like it has my shaky eye level zapping method beat all hollow. The newer version clamps onto the phone and lets you snap a shot of the site with the camera and get a picture with the level marked directly on it. Sounds a whole lot easier to have the pic right there to refer to. I still see the ES1500 out there for $15-20 and I’d still call it a Tool That Doesn’t Suck.  The newer version is double that, but might be worth the $40 if if gives you a permanent record right on a photograph. I’m gonna pick one up and let you know next month. In the meantime, I’ll continue using my TTDS, the Ryobi Phoneworks ES1500. Might work for you too.

Are You Connected to Your Water Feature?

Are you connected to your water feature? Sounds like an odd question? You might think I’m heading in the direction of getting you re-connected to nature. You know what I mean, how in today’s world we have a shortage of nature in our daily lives and having a water feature is a great way to remedy that problem. If you have children, your water feature can be their connection to nature as an outdoor classroom to study the eco-system without them even knowing it. All of that would make a good article however that’s not the direction I was heading.

Instead, I was just curious if your current water feature has a Wi-Fi connection? Now I bet I have your attention, you didn’t think your water feature needed a Wi-Fi connection did you?  Well in today’s world who would expect anything else?

With the addition of two new Atlantic Water Garden products your water feature can join the high tech world. Atlantic’s Triton Ionizer and pump variable speed control both have their own Wi-Fi connection making your life that much easier and your water feature more interactive.

The Triton Ionizer ionizer is designed to mineralize the water helping keep water features clean and clear without the use of harsh chemicals and is safe for fish.  The unit can be controlled manually from the front panel or by the use of the ionizer mobile Application for iPhone or Android devices.

The TidalWave VSC allows you to vary the output of Tidal Wave TT & TW-Series Asynchronous pumps wirelessly by remote control or mobile app! The VSC allows you to set both on and off times as well as drop to 25% of the total flow in 10 levels of adjustment giving you the ultimate control over water flow.

Both of these products make life with a water feature more enjoyable. Previously the downfall has always been the effort to disguise them into the landscape during installation usually ending up in a location that is tough to access. With the new connect ability, you can hang out on the patio and play with your pond from your lounge chair. You see some debris in the waterfall, open the ionizer app and increase the level. Or the reverse can be true, you don’t see any debris in the water feature, open the app and lower the level of activity.

The variable speed control is even a little more interactive, as your mood changes so can the desired flow of your waterfall. If you are having a party and want the waterfall to really put on a show, open the VSC app and turn up the volume or it could be a quiet afternoon on the patio, open the app and lower the volume a little. The VSC can also be programmed to control your feature with its on/off programmable timer. This is a nice little feature that helps you to save electricity and water by having it turn off when you are not around to enjoy it.

So sit back in that lounge chair and visit www.atlanticwatergardens.com and learn how you can get better connected to your water feature!

 

About the Author:
Sean is the Regional Sales Manager for the Southeast for Atlantic Water Gardens. Fish Geek and water feature enthusiast, Sean has managed one of the largest aquarium stores in the Southeast while running his own pond maintenance company.SEAN BELL

Sean is the Regional Sales Manager for the Southeast for Atlantic Water Gardens. Fish Geek and water feature enthusiast, Sean has managed one of the largest aquarium stores in the Southeast while running his own pond maintenance company. When it comes to water features, Sean is your guy!