Did my builder screw up by using 2HP pump but 1.5" pipe ?

[SPP]

Hello All,

I been reading hydraulics 101 by Mark ( an excellent work, thank you Mark ) and also plumbing FAQ by others.
I keep reading about maximum water velocity allowed and I was concern about my filter performance if water velocity is too high. I know anything moving too fast is not good for filters.

In one of my line of work with diesel engine fuel filtration system, maximum flow by engine total fuel demand ( burn & return ) and all pipe fittings ( elbow, reducers & etc ) is something I have always pay attention to. However pool is more complicated because of the long pipe run and so many elbows and so on. Worst of all, I never got involved in my pool building at all, I leave it to the so called "professional."

I am trying to source a Blue & White series 300 flow meter and fortunately there is a Indonesian dealer. I hope they stock what I need. I just emailed them.

It seems it is so wrong based on sources I am reading, that my fix mount 2HP Hayward Pump is married to 1.5" PVC pipe both suction and entire discharge piping. This is why I wanted to get that flowmeter to know how bad is the friction loss or whatever detrimental effect is going on. I been searcing the web to try to figure out what are the complete negative effects if a filtration system supposedly using a 2" pipe and instead 1.5" pipe installed but I can't find any.

I have a Pentair 1.5HP on trolley as back up. If needed, I may switch that with the 2 HP Hayward, so that my fix mount pump becomes 1.5HP and can run more effieciently with 1.5" plumbing. Next is to buy a new pump next time that Hayward come of age ( its only 2 years old now ). I also like the Pentair pump better, it is so much more quiet than the Hayward. Maybe the Hayward is noiser because of plumbing resistance of the pool, where my Pentair on trolley only has short in and out hoses. The motors are the same, Smith something. I maybe hearing impeller noise ??

Do I loose a lot of filtration capability or performance on a system with increased water velocity ?
Hayward guideline stated 6-8 feet/sec maximum for suction and 10 ft/sec maximum for disharge.

Vampire electric bills I can live with but filtration system not working at its best in terms of particle capture, I consider that a failure. Loosing money on electrical bills and at the same time not getting my investment from the filters...so sad. I rather dump some more money now and correct the filtering situation, regardless that 1.5" pipe is wrong to begin with. I can't change pipes, its all inside concrete.

The typical filter data sheet always put commercial operation must have lower flow for a typical filter or bigger filter than a residensial one. Its like 50% flow reduction for commercial filters application.

Now, filters always talk of GPM of flow, based on square feet of filter material. Pipe talk of GPM and water velocity.
For a smaller pipe to flow same GPM compared to next bigger pipe, water velocity must increase.

What actually will happen if my setup up of 2HP pump, which supposedly must use 2" pipe at least .....get plumbed with 1.5" pipe ?

The filters I have are designed with 2" port, but plumbed with 1.5". Is fair to say that I will have higher water velocity within the filter housing, even though the filters internal water plumbing are for 2" ( or sized at 2" ). I don't understand hydraulics to verify water velocity in this kind of scenario. All I know back pressure or total dynamic head will increase for sure due to smaller pipe size being used.

Anyone who can help, I will be most grateful.


Thanks,

Surya

 

[mas985]

SPP,

First off, for a given pump size, smaller pipe will have higher head loss and lower flow rates than larger diameter pumps. You can see the effect in one of the charts I have in the sticky (second post). It shows several plumbing systems combined with several pump sizes to give you an idea of what happens when you change pump size and/or pipe diameter.

Second, depending on how your plumbing is set up, small diameter pipe is not always that bad. If the plumber used multiple 1 1/2" runs from the pad to the pool for each skimmer, drain and set of returns, then this can be just as good as a single large diameter pipe. So maybe you could describe the plumbing in a bit more detail.

Also, in the second post of the sticky, I cover the meaning of flow rate maximum for PVC piping but the short answer is that the higher the flow rates are in piping the more likely it is that you can cause some damage with water hammer. So generally, you would like to adhere to the recommendations but if you exceed the flow rates it doesn't mean that something bad will happen only that it is more likely.

Given that it looks like you don't have a spa or any water features, I am not sure why the PB put such a large pump on that pool especially with small diameter pipe.

So I can help a bit more but I need more detailed information.

How is the plumbing laid out? Length of runs, number of runs, etc.

What is your current filter pressure?

Is the Whisperflo a 2 HP uprated or full rated pump (i.e. what is the service factor)?

 

[SPP]

Thank you very much Mark.

I will look into the hydraulic 101 in more detail after this.

In the mean time this is my data :

As per name plate on motor : A.O Smith / Hayward
The pump is Hayward Super Pump 2.0HP. SF is 1.0. This is a 50hz unit at 220V. The maximum ampere rating is 11.7, so its a 2,574 watts. I can't track model number thru Hayward www, I think because 50hz is special order for export and thus need to do special request for data sheet. Model number is C56M2U23 and there is SP-0150-2-1CM. Super Pump has part number that starts with SP as per www. Your list of 2.0 HP Super Pump stated 2,230 watts. Its quite common for 50hz unit to need more watts compared to 60hz units to do same amount of work. If I buy USA water pump with 60/50hz spec for marine air conditioners, using it at 50hz I usually loose 10% of the rating. The same if for air-cond compressors. I think the downrating figure is somewhere around 17% according to my friend who does air-cond. Anyway...

The photo is what the pool supplier stick on my wall. This is the only plumbing schematic I have.
POMPA means PUMP, the rest is easy to interpret.
However there are some things not written in that schematic.

- There is a check valve on the suction pipe in balancing tank. Suction pipe is about 7 feet below pump impeller.

- Now I have a Hayward cartridge filter dowstream of the sand filter

- The MAIN DRAIN suction pipe sits 14 feet below pool water surface

- The pump impeller is about 3 feet above pool water surface

- Due to space, sand filter is located about 9 feet ( its valve ) above the pump impeller or 12 feet above pool water surface

CONTINUE ............

 

[SPP]

My sand filter pressure when clean in about 5 psi before adding cartridge dowstream. Now its 10 psi clean and cartridge 3-5 psi clean.

My pool has 6 inlet nozzles. I do not have the schematic how they are plumbed but logic tells me that the builder seek lowest cost and I drew what I guess is their set up. I assume so because I can feel the power of water flow is weakest at the furthest nozzles, so I can guess how they plumb it. Total run of pipes is about 100 feet combined and including distance to pump.

Sorry for the poor drawing


CONTINUE.......

 

[SPP]

This is how the actual position of the pump and filters are

 

[SPP]

This is how the plumbing are on the suctions

Gee the area look dirty, must get my pool boy to be more disciplined

 

[SPP]

See the single inlet pipe into the pool, this is why I drew what I assumed to be the most likely way the 6 inlet nozzles of the pool are plumbed by builder/supplier.

 

[SPP]

Hello Mark,

Your 101 stated :

"The above plumbing scenarios are defined as a typical swimming pool plumbing system with 2" pad plumbing and varying suction and return pipe diameter as shown below. "


What is a PAD plumbing ?

Thanks
Surya

 

[SPP]

Hi Mark,

Correct me if I misunderstood the graph.
Page 2 ( post 2) in Hydraulic 101 shown that pump graph with different size piping.

My 2.0 HP Super pump is using 1.5" pipe suction and discharge, so it is scenario A
There the scenario A line intersect the 2.0HP at about 88 feet and 57GPM.
At my pump size, I should be using 2" suction and discharge pipes, so it should be scenario C, which is 77 feet of head and 92 GPM.

So if I use 2"/2", I will fall into -10% best efficiency, if I use 2.5" suction and 3" discharge as in scenario F, I will get best efficiency.

You were saying that we are afraid of water hammer and I know what you mean. In my old house I can hear pipe sound when someone turn the tap open and then close....scarry. In a pool its a circulation system, unlike house plumbing which is like and on/off cylce as far as pressure on pipes are concerned. I agree that water hammer happens when pump at first start up and if valves are closed, for pool plumbing that is. Valves being closed I don't worry, the only time valve is closed is when from filter mode to backwashing mode at the sand filter and the pump is turned off when such action takes place.

I am still wondering, if my plumbing system exceeded its GPM reccomendation...what loss do I get in terms of filtration efficieny?...if there is any. Kw per GPM I am sure I am loosing quite a bit due to water friction and more back pressure from the smaller 1.5" pipes.

Come to think about the whole thing, if I were to build a new pool, I would make sure I over size the pipes by at least 2 size and use reducer later when needed, just like you reccomended. If I am a pool pump supplier or builder , I will run a test with a few pumps of different power until I get the best efficiency. Paying say US$100-200 up front and save electricity and all other benefits from correct pump size for the next say 5-7 years of the pump life, is cheaper for sure.

My pool parts supplier was the one who designed the plumbing system and pump sizing. They knew the pool spec because they are also invloved in the pool design. All I said was I want the pool to be "X" size and the depths bla bla bla, they know how much water is in the pool. All was left to them to calculate.

I'll see what happens when I get my flowmeter, should be sent over to me by middle of this week.
I just downloaded the Hayward pump sizing PDF, its a simpler form of your Hydraulic 101 but enough information to know that 2" pipe should be choosen with my 2.0Hp super pump due to water velocity concern. Basically the Hayward pump sizing & piping manual guideline was not closely followed by them, otherwise pipes would be at least 2"/2" as per Hayward to begin with.

This is the problem with 3rd world countries like mine. Builder wants to save money or maximize profit or what ? They could have just told me to pay more for a say 3" pipe...I will do so in a blink. HHmmm, not good...


Regards,
Surya

 

[JasonLion]

Small pipes waste electricity but otherwise aren't so bad. The key to filter efficiency is to run at a flow rate below the rate the filter is designed for. The filters design flow rate doesn't necessarily have anything to do with the the pipes design flow rate. You don't want to keep increasing the pipe size without limit. It is actually possible to have too little resistance to flow in the pipes and be running the pump outside of it's ideal performance zone.

 

[SPP]

Yes, I just read that electricity cost thread for the pump. Interesting read. I never actually measure a pump electrical demand to that detail yet. Anyway, looking at various publication, 2"/2" is a minimum for my 2.0Hp pump. I can always create restriction later but I can' recover the current parasitic resitance from too much water velocity...so sad.

 

[mas985]

SPP quite a setup you have there. I will try to answer some of your questions below in bold.

Hi Mark,

Correct me if I misunderstood the graph.
Page 2 ( post 2) in Hydraulic 101 shown that pump graph with different size piping.

My 2.0 HP Super pump is using 1.5" pipe suction and discharge, so it is scenario A
There the scenario A line intersect the 2.0HP at about 88 feet and 57GPM.
At my pump size, I should be using 2" suction and discharge pipes, so it should be scenario C, which is 77 feet of head and 92 GPM.

I am not sure what you are getting at here. Are you suggesting that you want to change your current plumbing? Normally, this is very difficult and expensive so I wouldn't suggest doing that. Usually, you can find a proper pump for nearly any type of plumbing. Also, note that the super pump has a service factor of 1.0 so your pump is closer to the 1 HP (1.9 BHP) pump shown in those curves. So your plumbing is probably somewhere between A and B with the pump being close to the 1 HP (1.9 BHP) curve. So for scenario A, that would be about 77' of head @ 52 GPM.

So if I use 2"/2", I will fall into -10% best efficiency, if I use 2.5" suction and 3" discharge as in scenario F, I will get best efficiency.

You were saying that we are afraid of water hammer and I know what you mean. In my old house I can hear pipe sound when someone turn the tap open and then close....scarry. In a pool its a circulation system, unlike house plumbing which is like and on/off cylce as far as pressure on pipes are concerned. I agree that water hammer happens when pump at first start up and if valves are closed, for pool plumbing that is. Valves being closed I don't worry, the only time valve is closed is when from filter mode to backwashing mode at the sand filter and the pump is turned off when such action takes place.

I am not afraid of water hammer, I was only explaining why it is not a good idea to exceed recommended flow rates. It is pretty rare for pool plumbing to experience water hammer but it can happen. Normally, turning on and off the pump will not cause much water hammer but if you have a check valve then this can slam shut and create water hammer. Most of the time though this is not an issue.

I am still wondering, if my plumbing system exceeded its GPM reccomendation...what loss do I get in terms of filtration efficieny?...if there is any. Kw per GPM I am sure I am loosing quite a bit due to water friction and more back pressure from the smaller 1.5" pipes.

You can damage a filter by exceeding it's recommended flow rate but it is difficult to know for sure, unless you have a flow meter.

Come to think about the whole thing, if I were to build a new pool, I would make sure I over size the pipes by at least 2 size and use reducer later when needed, just like you reccomended. If I am a pool pump supplier or builder , I will run a test with a few pumps of different power until I get the best efficiency. Paying say US$100-200 up front and save electricity and all other benefits from correct pump size for the next say 5-7 years of the pump life, is cheaper for sure.

My pool parts supplier was the one who designed the plumbing system and pump sizing. They knew the pool spec because they are also invloved in the pool design. All I said was I want the pool to be "X" size and the depths bla bla bla, they know how much water is in the pool. All was left to them to calculate.

I'll see what happens when I get my flowmeter, should be sent over to me by middle of this week.
I just downloaded the Hayward pump sizing PDF, its a simpler form of your Hydraulic 101 but enough information to know that 2" pipe should be choosen with my 2.0Hp super pump due to water velocity concern. Basically the Hayward pump sizing & piping manual guideline was not closely followed by them, otherwise pipes would be at least 2"/2" as per Hayward to begin with.

This is the problem with 3rd world countries like mine. Builder wants to save money or maximize profit or what ? They could have just told me to pay more for a say 3" pipe...I will do so in a blink. HHmmm, not good...


Regards,
Surya

Most pool builders (in any country) really don't understand hydraulics very well. They simply do what has been taught to them without any regard to what might be better. Two things to always remember when building a pool: Big Pipes, Small Pump. Of course there are times when a big pump is necessary (i.e. spa, waterfalls, etc.) but then you need really big pipes.

I would say your 2 HP Super Pump is probably slightly oversized for your plumbing. If you don't need the 2 HP, than a 3/4 HP Super Pump is probably more than enough pump for your pool.

 

[SPP]

Hello Mark,

Thanks for the reply.
Now way I will re do my piping.... :lol:
OOppss, I read your graph at 2HP not 2 BHP, so sorry.

With 2"/2", I can get closer to the efficient point, what a waste yes ??
I got the flowmeter today and I will install it tomorow. Went to the hardware store and can't get a 5/8" spade cutter.
So I bought a 5/8 concrete drill bit...ha ha ha. I will try on a used 1.5" PVC first, see how is the result of the drill hole using such drill bit, but I will make the hole first with 1/2 regular sharp drill bit.

SPP

 

[SPP]

I am so sad...

I got the flow meter running.
I have always assumed I am getting at least 85 GPM flow, which is like 67 feet head loss in a 2HP ( 1.9BHP ) pump.

Sand 12 psi / cartridge 15 psi = 33 GPM 17.6 hrs 1 turnover...holy cow !!!
Sand 12 psi / cartridge 5 psi = 49 GPM 11.9 hours 1 turnover.

Sand clean is 10 psi. Cartidge clean is 5 psi ( 3 psi with high pressure wash...I am afraid it will get damage )
So based on 1.9 BHP Super Pump, I am having a head of about 77 feet...wow, that's a lot.

I don't know what is the head loss equivalent that the 1.5"/1.5" did to my plumbing if compared to ( by right ) a 2"/2" plumbing.

I am ordering swing check valves to replace the high-loss plunger type I am using...I hope to reduce head loss.


Now let me calculate backwards my total Plumbing Head Loss:

FILTER
My filter pressure, I will calculate at the sand one since it is upstream. 12 psi is = 2.31 feet x 12 = 28 feet head loss

SUCTION
Hayward estimate for 2HP with 2" suction, the loss is 13.5 to 16 feet. I am using 1.5", so assumed at least 20 feet loss here


OTHER LOSS
Now I have about 29 feet of head loss equivalent from plumbing total length, pipe size ( wrong size that is !!! ), Tees, ball valves, elbows, check valves, 6 water nozzles and whatever else I miss. IS THIS ALOT ?

The Blue White series 300 flowmeter I am using stated +-10% accuracy...I hope mine is +10% wrong...

Thanks
SPP

 

[mas985]

I guess I didn't catch this before but you have two filters? This will increase your head loss by some. If I understand you correctly, the cartidge has 5 PSI lower than the sand filter which means you are losing 5 PSI in the sand filter.

Now that you have the flow rates, it is best to use the SuperPump head curve directly. For example, 49 GPM is at about 43 feet of head.

I am a little confused with all of the PSIs you are throwing out. I am not sure what the real PSI is. Can you post the flow rate and both PSIs with both the sand and cartridge filters clean?

 

[SPP]

Hi Mark,

Yes, I have two filters. One is sand and downstream of that is cartridge.
When I first installed the flowmeter, at that time the cartridge was dirty at 15 psi and sand relatively clean.
With this I got 33 GPM only, registered by the flow meter.


If sand is clean, I can get 10 psi on its gauge it and if cartridge is clean I can get 5 psi on its gauge.

So cartridge was cleaned after that and I got 5 psi from cartridge, while sand was at 12 psi because I did not backwash it.
With this almost very clean filters, I got only 49 GPM on the flowmeter.

I use the 1.9BHP on the chart, because my pump is 2.0HP at SF 1.0.

So looking at 49 GPM of flow, that means I am having an equivalent of 77 feet head loss as per 1.9BHP motor curve.


I was just trying to figure out what made up of the total of 77 feet of head loss equivalent.


Since my sand is at 12 PSI, I tried to convert it to feet of head equivalent by multipling 2.31. Since sand is before the cartridge, I do not need to calculate the PSI reading of cartridge filter. Is this correct ?
I am assuming my both filters have slow down my pump in an equivalent head loss of 12 psi x 2.31 = 28 feet.

I am also trying to convert the loss during suction and I put 20 feet of head loss equivalent.

Now, those two above made 48 feet of total head loss equivalent

So, next head loss is from water movement, length of pipes, elbows, tees, check valves and etc, this is why I was asking if 29 feet head loss ( 77 - 48 = 29 ) is normal ? If my pipes were all 2", instead of 1.5", I was wondering what reduction of head loss I can expect.

If usually 65 feet of head loss is expected in a typical pool, I would be happy, because I would have got 75GPM from my 1.9 BHP pump.

This is why I am so sad. I been assuming all this time I am getting 75GPM.
If my PB were more careful in his plumbing calculation and use bigger pipes, better soft bend elbows, better check valves
( swing ones ) and whatever efficient way water can be moved, I would loose less.

Its not the electric bill here I am concerned. At clean filter and only 49GPM, that means 11.9 hours of 1 pool water turnover in my 35,000 gallon pool, I would say I am screwed. I expected 8 hours per 1 pool water turnover is the minimal design target for residential pool.

I can't redo plumbing deep within the concrete. This is why I am ******.
Its my decision that I added cartridge filter after the pool is built, but at 5 psi clean, that is 11.55 feet of head loss equivalent only and the water clarity is worth it.

I started this thread because I worry that the 1.5" all around pipes used is too small for my 2HP pump after I read Hayward reccomendation of 2".

Thanks Mark.

 

[SPP]

Hi Mark,

I got this on-line calulator....finally. I have searched wrong all this time.
I got it while refine searching for the keyword :

The head loss is inversely proportional to the diameter of the pipe


Pipe pressure loss calculator


I tried calculating what is the head loss increase if my pool using supposedly 2" pipes and instead has 1.5".

My data entry as follows :

Pipe type : PVC, Plastic, Glass
Pipe Diameter : 38mm ( 1.5" ) and 50mm ( 2")
Pipe Length : 30 meters ( 99 feet )

Fluid Type : Water at 20 * Celsius
Flow Rate ( M3/ Hour ) : 11 cubic meter/hour ( 48.5 GPM )

Minor Loss Coeff : Zero

At 1.5" pipe size, I am getting head loss at 5.32 meters, which is 17.55 feet
At 2" pipe size, I am getting head loss of 1.43 meters , which is 4.72 feet

So here I am getting extra head loss of 12.83 feet equivalent just because my PB used 1.5" pipe.

I could have reduced my current heady lost of 77 , by 12.83 = 64.xx feet of head loss only

64 feet of head lost will allow my 2.0HP pump to move approx 74 GPM, instead of current 49 GPM.

64 feet of head loss is the high side of the typical pool, as per your 101.

Now I am sooooooo ****** with my PB.

 

[mas985]

Ok I think I know what may be throwing your numbers off some. The chart in the sticky is not a very good representation of your pump. That pump curve is for the Whisperflo series of pumps. Although the BHP is about the same, the head curves between your pump and that pump is actually a bit different. Your best bet is to look at the actual data for the SuperPump. That can be found here.

Also, note that your Sand filter gives you a pretty good estimate of TOTAL return head. So you don't have to add anything to that number. Assuming clean filters, your sand filter runs at 10 PSI which means your total return head is about 23 ft. However, you only have 49 GPM so your suction head must be pretty high. Using the SuperPump data and extrapolating some, you can get to a total system head of about 70 ft. This is close to the pump curve in the sticky but off about 10%. So in summary:

Total Return Head = 23'
Total Suction Head = 47' (really high could be something wrong here)
Total System Head = Return Head + Suction Head = 70'

I would check your suction side to make sure you don't have any blockage because the suction head should not be that high. For most pools, suction head is well below return head.

As for your pump, since your flow rate is only 49 GPM, there really is no chance of any damage to your plumbing system. The pump you have now is fine, just not very efficient so if you want something more efficient then look into another pump. Otherwise stick with what you have.

 

[SPP]

OK Chief...thank you very much. What would I do without you.... :-D

I will look into the suction side carefully. I know it broke the 10x pipe diameter rule for the need of a straight pipe into a pump inlet. But its the space constraint.

Check valve I will change soon, its on order from USA. Everything must be imported...hhhmmm.
NowI got new task....thank u Mark.