Hydraulics 101 - Have you lost your head?

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investindy said:
21000gal pool
3 turns a day this equals 21000x3 = 63,000gallons pumped per day
63000 gallons / (60x24) = 43.75 gallons needed per minute [60minutes an hour x 24 hours]
My pump pressure shows 28PSI thus 28x2.31 + 5 = 70 for head pressure

- Look at a pump manufacturers chart for something with 70lbs head pressure and a GPM of 44, for my needs around 3/4HP
- If I wanted the most energy efficient it would be around 1Hp but then I would get 65GPM so I would only need to run my pump (21000/(65*60)) = 5.4 hrs day for one turn.
Click to expand...

Not quite that easy...

Your head pressure is 'dynamic' because it changes with water flow. That means when you change the pump size, the head will change with it.

You need to start with your GPM at the known head level and then find your target GPM. To find the new head:

New Head = Known Head X ( Target GPM / Known GPM )^2

So, let's say you have 63 GPM @ 46' Head and you need to get to 75 GPM. The increased water flow will bring your TDH from 46' up to 66'.

You can then use that new head level and your target GPM to size your pump.

*Thanks to Pentair for doing the math for me on the example.
 
Not every pool will fall into this range but most should. I got these ratios from a hydraulics model that I developed and have calibrated with a couple dozen pools. So by knowing a few key parameters about the system, I can fairly accurately predict head loss and flow rates for various pumps.

There are a few things which will push you outside of these ranges but they should at least be close to the average pool.

Next, the one thing which screws this whole thing up is the filter gauge. They tend to get inaccurate over time and can account for a lot of error.

You state that you are using a 3/4 HP Hayward SuperPump but that pump will support about a maximum of 50’ of head @ 31 GPM so something must be wrong with your gauge or you really have a 3/4 HP SuperII which is a much more powerful pump. But even then the numbers don't work.

For a standard plumbing setup with 1-1 ½”suction line, 1-1 ½” return line, filter, heater and pool to pad separation of 40’, a ¾ HP Max rated SuperPump would have the following performance:

Flow Rate 41 GPM
Suction Head = 19’
Return Head = 25’
Filter Pressure = 11 PSI

For a Northstar full rated ¾ HP:

Flow Rate 49 GPM
Suction Head = 28’
Return Head = 36’
Filter Pressure = 16 PSI

So it is very difficult to get that kind of pressure with only a ¾ HP pump. Even a 2 HP pump would only produce 22 PSI. If you are running solar or have very long lines to the pool, then perhaps you could have that kind of pressure with a larger HP pump but a ¾ HP Max Rated SuperPump would never get to 28 PSI. The head curve doesn't support it.
 
Well my curiosity is peaked....Really all I know for sure is that the motor label says 3/4HP and the pump says superflow and the picture matches it, but I dont know if the previous owner had matched the right pump/motor....He did say something about its a newer motor but I never thought to ask if it was a like for like (smaller motor for original pump?). As long as the motor has the same frame series someone could of made an odd combo. I will need to research this.

I will get my numbers again with the newer gauges and report back what my measured head pressure is....This will give another example for the thread (the right way).
 
I misread your post. I thought that you had written that it was a SuperPump not a SuperFlo. Pentair makes a SuperFlo pump. Does the pump look like this?

I have never seen a Hayward Superflow and there are few references to it on the web other than forums.

A picture of the pump might help identify it.
 
All I know is that it is a super pump and looks like the ones from this link:

http://www.haywardnet.com/aboveground/p ... .cfm#pumps

The motor plate (not a Hayward) says 3/4HP.....I know its the superpump and has 1.5" connectors in/out so that narrows down just based off connections the possibilities but I still don't know which of the three series of Super pump it is, or if even the acutal pump part is constant across the three versions and they only change HP (assuming but I dont know). Studied the nameplate for several minutes and its Completely worn off...Looks like MAYBE a "2" as the first digit but I'm not confident thats what it is. Only digit I could kinda make out.

Anyone know how to narrow down which series and model of the super pump I may have?

I still need to get another gauge to verify the 28PSI.
 
Sorry for the confusion. In your post, you called it a SuperFlow which made me think it was a Pentair.

So if the pump says Hayward and the motor is a 3/4 HP with a service factor of 1 or not printed on the motor label, then that indeed is a Hayward 3/4 HP Uprated SuperPump.

That pump should not be able to achieve 28 PSI (65' of return head) unless, the pump is 15+ feet below the surface of the pool.
 
My whisperflo 3/4 HP comes in very close to the GPM listed using gauges, thus dialed right in for an 8 hour turn...I am wondering about how this ties into the energy usage...I'm lost :bump: lost in the thread about SF and BHP....So is my energy usage approximate as shown, or are there other factors for true energy usage of the pump based on its over/under optimum curve? Is real power usage, power usage x SF?

Just not following....lso, thread mentions general rule size for 3 turns but other threads say run it 1 turn a day? Guessing extra capacity is for filtering out problems?
 
A 3/4 HP Whisperflo will use about 1.3 kw of energy near right side of head curve. The service factor & BHP is usually specified at near maximum power which is close to the maximum GPM. As you move left on the head curve, the energy use drops a bit but not by much (~0.33%/GPM).

Another way to measure power is via the power company's meter on the side of your house. This is the power that really matters since they are charging you for it. You would need to take two measurements, one with the pump off and one on to find the pump energy. Some of the newer meters have direct kw readout while the older types have wheel that you need to count revolutions and apply a correction factor. Let me know if your interested in this but I need to know your meter model number to give you more information.

As for turnover, most pools need 1-2 turnovers per day. It is a range because it depends on the operating conditions and what is falling in the pool. In winter, I run at 1/2 a turnover and the heat of summer, 2 turnovers.
 
I have read through this excellent post twice, I'm either to dumb to get it or I can't cope with the english terms. I like to think it depends on lack in english knowledge, but I'm not hundred percent sure :?

If I describe my situation briefly someone might be able to help me with my choice in choosing pump and filter.

Approx 16K gallons of water
2 skimmers
1 bottomdrain
2 inlets.
All plumbing is thought to be done with 2" tubes
Pump and filter is placed at the same level as the bottom of the pool
less than 3m tube from each skimmer/drain to the pump.
less than 15m from each inlet to the pump(seperate lines).
Heat pump placed less than 12m from the pump(above ground).

I have decided to use a cartridge filter. Besides from that I'm not sure of anything.
I would like to be able to turn over the water atleast 3times/day.
I can also say that I have looked into Haywards swimclear series and would like to dimension that filter as big as possible without being stupid. I have read here numerous of times that one should overdimension the filter, I guess there is a limit when overdimension is not defensible anymore. But I have no problem with paying more initial if it can help us to maintain the pool with the less effort throughout the many years to come.

Any help is much appreciated
//Mats
 

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For a 16,000 gallon pool and a 8 hour turnover (i.e. 3x per day), you would only need 33 GPM from a pump. Even the smallest pump will deliver much more than 33 GPM so assuming you don't need a high flow rate for a spa, waterfall or other feature, either a two speed or variable speed pump might be a good solution.

If you go with a variable speed, the Intelliflo series is probably your best bet. The other variables have not had a lot of time out in the field so reliability could still be an issue. Depending on what you pay in electrical rates, the Intelliflo will likely pay for itself in a short period of time. If I were buying a pump today, this would be the pump.

If you go with a two speed, there are many options depending on the brand you want to use. You could go with a 1/2 HP but some manufactures use 3/4 HP motors in those pumps so the efficiency isn't that great which is why I usually recommend a 3/4 HP full rated pump as the smallest.
 
Thanks Mark!
From my half hour search yesterday I coulden't find any dealer who sell Pentairs products in Sweden.
If someone know's a trustable site within Europe please tell.
I saw there was to different types of intelliflo pumps. Never really understood the difference between the two.
One had 4 different settings, If the settings was preset from the factory was something I coulden't figuring out. The other one(3,2kw) was from my understanding free to operate with whatever flowrate you find appropriate. So I guess that is the model to go with!
If you have the time I appreciate all the info I can get(I'm not lazy, I read what I could find yesterday, but opinions from a genius like you shall never be underestimated 8) )
I wonder if the quality of the pump goes hand in hand with it's technical brilliance! I have to find a reseller in EU though, so I can get spareparts and service before I consider to buy it.
I can see the benefits with a pump with different flows from my situation. If things goes like I have them planned I will run the heatpump during the nights. It would save energy if I could set excactly the flow the heatpump needs instead if running full flow through the bypass valve.


I have a few questions about Cartridge filter Mark, I hope you will spread some light on that subject aswell :-D I will start a new thread so I don't hijacking anything, in few days. I'm little busy at the moment. I will Pour the concrete to our pool Tomorrow or the day after :goodjob:

Thanks!!
 
Try this link. At least it gives you a contact which might be able to tell you where you can purchase the pump.

There are two pumps in the Intelliflo series. The variable speed and the variable flow.

The variable speed allows you to set the pump up for 4 different RPM speeds. However for a fixed speed, flow rates will change with changing head loss (e.g. when go from pool mode to spa model) but since you have four speeds, that usually is not a problem. Each of the 4 RPM settings are adjustable so the controller can switch a setting with a change in the plumbing. But then you need the controller too.

Variable flow allows you to set a constant flow rate no matter how your plumbing valves are set or head loss seen by the pump. The RPM will automatically change to get back to the same flow rate with a change in head loss. This is more of a set and forget pump. Also, if you don't have a spa or water features, you could operate it without a controller. Basically set it to one flow rate and leave it alone.
 
In reference to measuring suction side vacuum, would it be acceptable to measure this at the strainer basket drain plug, or does it need to be upstream in the pipe? Also, for the pressure side, I'm assuming the pressure gauge on the filter is acceptable?

Thanks.
Jeff
 
Yes, the pump drain plug is a good place to measure the vacuum pressure.

The filter pressure gauge is normally fine for measuring pressure. You should check for signs that it might be broken before depending on it. Filter pressure gauges tend to break after only a few years. At a minimum, make sure that the gauge reads zero when the pump is off and moves to a non-zero reading when the pump is on.
 
A couple of options to get more life out of a pressure gauge:

1. Install a liquid filled version (they handle pressure fluctuations better)
2. Install a shut-off going to the pressure gauge and open only for your readings (minimizes fluctuations on the gauge).
 
1. Install a liquid filled version (they handle pressure fluctuations better)
2. Install a shut-off going to the pressure gauge and open only for your readings (minimizes fluctuations on the gauge).
Click to expand...
I like #1 but not so crazy about #2.

I would personally be more comfortable to have the pressure monitored constantly on any operating pool circulatory system. It is often the first indicator that something is not right. At 7-8 bucks, the longevity of a psi guage seems somewhat irrelevant.
 
Prepping for a potential new pump...and just validating what the builder created for me.

Current pump: PacFab Challenger 2.5 HP High Head (Uprated)
Filter: TA100D
Lines: 2" Coming and Going
Spa: 5 returns, 2 drains
Pool: 3 returns, 1 drain, 1 skimmer (drain is plumbed into skimmer base)
Heater: yes
Solar: not at this time
Cleaner: pressure side 1.5" pipe
Pool: About 20K gallons
Water feature: the spa overflows to the pool, and there is a small amount of bypass water that goes to the spa in pool mode
Note: The pump sits several feet above the pool level, the spa sits higher than the pool (but still below the equipment).

Pool Mode Measurements:
Suction: 1.13 * 19 = 21.5
Pressure: 2.31 * 14 = 32.5
Total Head: 54

Spa Mode Measurements:
Suction: 1.13 * 8 = 9
Pressure: 2.31 * 28 = 64.5
Total 73.5

Thoughts?
Jeff
 
The gurus will have to weigh in on that brand of pump. The things I would be concerned about:

1. Am I going to be able to use the same voltage source (ie 110v vs 220v)? - Potential extra expense.
2. Does this pumps setup when installed fall in the ideal curve for it? - See the beginning of this thread.
3. Is the new setups GPM going to provide 2-3 turns a day? - Suggested minimum range for 24hrs.
4. How much replumbing needs to be done to change this over? - Potential extra cost.
5. What am I truly gaining upgrading? - Purchase cost Savings, Lifespan, Performance, Energy Savings??
 
chumbley, if I am following correctly you have a single pump for both the pool and spa. That is a fairly common setup. The pump is normally sized for what the spa needs, and is too large for the pool. There can be a significant savings of electricity if you get a two speed, or variable speed, pump. The pool can use low speed, and the spa can use high speed.
 

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