Hydraulics 101 - Have you lost your head?

Suley

LifeTime Supporter
May 31, 2011
228
Los Angeles, CA
WOW WOW WOW WOW WOW!

I am glad to have met you mark! Exactly what I was looking for!!! Thanks for all the time you spend developing those excel sheets.... I plotted rpm vs psi for my pump and saw how time consuming it was to get the data!

Really appreciate your hard work!

Thanks Thanks Thanks Thanks! :whoot:
 

mas985

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Thanks! That makes it worth all the work I put in to it. Let me know if you have any questions and/or suggestions.
 
G

Guest

Thank you. the Hydraulics 101 spreadsheet is incredible. I really appreciate all the work involved in putting it together.
 

jblizzle

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May 19, 2010
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JasonLion said:
The links to download the spreadsheets are in the third post of this topic, back on the first page.

Call me crazy, but I can not find the links to the spreadsheets. I see some of the posts were edited last month ... were the spreadsheets removed?

I have a lot of questions about my current set up and what I would like to change, but was hoping to do a little investigating/calculating before creating the post.

Thanks,
Jason
 

mas985

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No, are aren't going crazy and I should have posted a more detailed explanation so here it is:

There were a couple of reasons that I removed the spreadsheet. The most disturbing to me was that I found web sites that were posting the spreadsheet without giving any credit to TFP or myself. Plus, I didn't want a commercial company to benefit from my work without compensation.
I had no problem with true pool owners, especially those that have contributed to TFP, using it for there own benefit.

However, the second problem I found was with the watts to GPM estimates. The curve fitting was based upon the CEC data when I inverted the curve to determine GPM from watts, a very small error in watts resulted in a very large error in GPM so the actual watts measurement turned out to be important. Several users of the model had discovered issues with the results at low RPM and I had many questions coming my way on how to properly use the model to get a reasonable answer. So I ended up performing a more detailed analysis using my full hydraulics and I found that it took much less of my time to perform the analysis in the first place than it was to "teach" others. Plus it allows me to get more insight into other plumbing systems/configurations so it really benefits me to further hone the models.

Plus not all that many folks are truly interested in getting the operating points to the plumbing system and for those who are only interested in a rough estimate to their variable speed pumps, I do have some approximations listed in the beginning section of this thread.

In the future I may post the spreadsheet again, but next time will be limited to TFP contributors only and I will track downloads much better.

So the bottom line is if you can give the as much detail about your system, I can then give you the best answer I can for the operating point of the pump. As a minimum, I ususally ask the following:

Pump Make/Model
Filter Type and backwash valve model if known
Filter PSI reading at the desired valve settings and pump full speed.
Optional: Pump suction reading (in-hg) - not necessary but improves accuracy
Heater - yes or no
Pool/Spa valve - yes or no

Suction side plumbing system description: # runs pool to equipment, pipe size
Return side plumbing system description: # runs pool to equipment, pipe size, number eyeballs, and eyeball diameter

Also, note that once you have the plumbing curve for your plumbing, that same curve can be used for any pump head curve to get the operating point. This is useful when deciding on a new pump.
 

jblizzle

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mas985 said:
No, are aren't going crazy and I should have posted a more detailed explanation so here it is:

Ok, thanks for clearing that up. Like I said, I have a lot of questions about my current capabilities and the possibility of being able to add the solar system I want. I had you in mind to hopefully answer them based on these extensive posts :wink: Rather than contacting you directly, I will create a new thread so other members possible benefits in the next few days.

I am already picturing a VERY long post to get all the information covered and not looking forward to writing it :)
 

doncaruana

LifeTime Supporter
Aug 25, 2011
408
Northville, Mi
Really bummed you pulled this. I was kind of excited about getting a simple "rule of thumb" kind of number for my pump. I loved the idea of wattage / gpm.
 

mas985

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The problem was that it was not very accurate using wattage as an input so people were getting some pretty wild answers. I found that the more accurate method is to start with details about the plumbing and filter pressure and work it out from there. If you are interested in getting some help working this out, please start a new thread.
 

bzeller

Well-known member
May 9, 2013
138
Round Rock, TX
Trying to absorb all of this and understand it. I'm building a pool and I want to be try to insure the PB specifies the best plumbing and pump scenario possible to maximize efficiency and cost. I'm not sure I fully understand Tables 1 and 2 under plumbing considerations.

1. Is T1 saying that in 2.5" plumbing, moving 90 gpm gives me WFR of 6 ft/sec and 119 gpm gives me WFR of 8 ft/sec? The previous paragraph states the table highlights recommended flow rates for three different velocity specifications, but I only see two?

2. So does pipe size affect return or spa jet strength? One PB was trying to tell me that it was better to use smaller plumbing so that you would get more "power" out of the returns for circulation, etc. Given what I've read here, I'm not sure that makes sense to me. If I understand correctly, larger pipe will reduce head loss allowing the VS pump to run at slower RPM to move the same amount of water. If moving water at a given flow rate, the pressure out a given sized jet will be the same whether 3" pipe was used or 1.5" pipe was used. The only difference will be that my pump ran more efficiently with the 3" pipe since it did not have as much head loss, correct?

3. When looking at T2 and discussing parallel pipes, that would basically mean you could have some sort of manifold at the pad for 3 1.5" returns and that would almost be the equivalent of one 2.5" return?

Thanks,
Benjie
 

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Isaac-1

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May 10, 2010
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1, I have not looked at this lately so don't know

2, this is a common misconception and people trying to apply "common sense" to physics, it does not always work the way people think it would, but without getting into the details of fluid dynamics, pressure does not increase by making a pipe smaller. Bigger pipe is ALWAYS better, it just turns into a point of diminishing returns.

3, from memory 3 1.5 inch pipes are about equal in flow capacity to 1 2.5 inch

If you start a new thread telling us more about your pool plans we can help give specific advice
 

mas985

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#1 - Sorry, that was a typo. Originally the table had three velocities, now it only has two 6 ft/sec and 8 ft/sec. These are specifications in the APSP-15 requirements.

#2 - As Isaac points out larger pipe is usually better. However, the PB may be talking about the jet orifice size. In this case, smaller orifice creates higher velocity so the jets feels stronger so you can get away with lower flow rates. This is why a 3/8" jet at 15 GPM can feel the same as a 7/16" jet at 20 GPM. But in any case, the pipe leading to the jet needs to be large enough to handle the flow rate. That is why I put together the Spa Pipe table with the jet size because they need to be designed together. Just a warning, most PBs seem to screw up spas so be careful and don't let them talk you into a bad design.

#3 - Yes that is correct.
 

imrodee

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saving this for later................. when I have more time.
 

SPP

LifeTime Supporter
Apr 6, 2008
306
Indonesia
Hi All,

Long time no write.
I just want to add some info to this excellent thread.

Those from countries with 50Hz ( mainly Asian and Europe ) electric supply please request proper pump curve based on 50HZ.
Most US brands like Hayward and Pentair will show 60HZ pump model and they run faster and has approx 23% more output than the 50hz cousin.

I am a victim to such misinformed data on my main pump, the Hayward.
The best solution I have done was, I install a flow meter. Its cheap, under US$150 for mechanical one.
This read all parasitic value of elbows and so on.

As an illustration to what mas985 indicated that check valve will create poorer water flow and some are worse than other.

This is using my trolley pump, a 2nd pump I use to assist main pump. I can easily remove any check valve to test.

With Check Valve. Cheapo ball type.
[attachment=1:1uxulj6g]With check valve.jpg[/attachment:1uxulj6g]



If No check valve at all. Sorry this trolley pump does not have flow meter to show real GPM. The flowmeter need PVC pipe and some straight section to install.
[attachment=0:1uxulj6g]Without check valve.jpg[/attachment:1uxulj6g]


I did use model below :
BestCheckValve.jpg

For my main stationary pump and the vacuum gauge shows improvement.


The mistake my pool builder made which I can not fix is : 2 HP Hayward pump using 1.5" PVC all the way.
I did some math years ago and I paid 20% extra energy bill or US$360 per year ( for approx 7 years now ) for the loss of the flow due to small pipe. In other words, I could get better flow for the same energy bill if 2" PVC as output pipes were used and combined with perhaps 2.5 in suction pipes.

So this thread is so useful. Too bad I join this forum after my pool was built. :rant:

Later guys.
 

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jblizzle

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Actually the cost to run a pump is a function of flow rate. With bigger pipe, the pump would move more water and thus cost more electricity to run. So assuming you ran the same amount of time, bigger pipe would have cost you more money.

Now if you knew the flow rate was higher and compensated by running less time to move the same amount of water, then you may have saved money. But we generally put little value in knowing the flow rate, since you just need to run the pump long enough to keep it clean to your liking.
 

SPP

LifeTime Supporter
Apr 6, 2008
306
Indonesia
Hi Jason,

OK, I will check with my amps meter and see what I am consuming now against nameplate.
I am only after faster turnover, this pump is 24/7 and only stop when bearing or impeller start needing overhaul.
I am now getting so much performance loss by having less turnover per day since the flow meter shows that its well below pool builder calculation.

Thanks very much J.

SP
 

jblizzle

Mod Squad
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May 19, 2010
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Why are you running the pump that much? Have you read the article in Pool School about run time?
 

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