1 hour pool turnover and moving water - possible ?

[SPP]

Hi My Seniors,

Me need some help.
Its been said that at least 6-7 times the water turnover, then the pool water gets a 100% filtration.
I completely agree, in fact my database seems to show 9 times being best and that need a 1 micron slime bag assisting.

One of my boss is making a pool. Target size is 20 meter long x 4.5 meters wide x 1.5 meters = 135,000 liters of water.
I been thinking, in my city high airborne dust, 8 hours per turnover is borderline and recovery is slow at this 8 hours.
Recovery meaning people in pool causing reduced clarity.

My 135,000 liters pool to have great clarity stability, I need my 2HP pump to run 24/7 non stop 365 days a year and come bather load, the extra 1.5HP on trolley will be used to assist.

My friend's pool of 225,000 liters now uses 4 x 1.5HP to get the clarity stability and recovery similar to my pool and that is an approx 4.7 hours per turnover.

Keeping aside pumps and filters cost, I did the calculation on the electrical power requirement which for my city is at US$0.15 per KwHour, if I use 14 of 0.75HP pump at 15 psi head loss but run it for 2 hours a day or 2x turnover and add 1 of 0.75HP as an 8 hour pump to circulate top layer of water which I assumed will have its chlorine reduced by sunlight during day time, the electrical cost is lower than 8 hour turnover 2 x 1.5HP pumps but running 24 hours a day.

The catch is, I must create a moving water to reduce mixing of old and filtered water like in a conventional pool.
At 1 hour turnover of 135,000 liters per hour group of pumps, I can in theory will make the water move 33 centimeters a minute from one end of the 20 meter pool to the other end. Place water injection/inlets on one end and suctions on opposite end . Imagining the pool as though as a 4.5 meter wide and 20 meter long pipe

I am betting that moving the water at this mild velocity will create a near perfect filtering opportunity based on my own assumption that unfiltered water now can't mix easily with filtered water like in our conventional pool. All I need to do is install 14 of 2 inch PVC pipes with no jetting adapter on one pool end wall and install 14 of 2 inch pipes as suction on the opposite pool wall , covered by some sort of protective mesh as wide as 4.5 meter by 1.5 meters so that people do not get sucked buy the pipes

Overflow system as I seen, even in endless pool, only get the top water moving but not the entire water column....correct ?

I am basing this pool "imagination" from a clean room scenario.
In a clean room, fresh air at low pressure is injected ( properly filtered ), by having higher pressure in the clean room, no way ambient airborne dust can enter the clean room. This to me is the moving of the water in the pool. For a clean room it is cheaper and more effective to inject clean fresh air this way than to filter out the entire clean room air if ambient airborne dust can find its way into the clean room.

On my dives, I seen water current bring dirty water or clean water to say a reef, but of course the current speed is approx 0.5 to 1 knot or 900ish to 1,856 meters per hour, not 20 meters per hour like I intended to create in the pool

Do you guys think what I am imagining here will result in a fast clarity recovery and at the same time 2x turnover a day will yield better than an 8 hour turnover 3 times a day ?

Many thanks
.

 

[jblizzle]

I feel like you are over thinking things ... Although admittedly I did not read very carefully Many people here turn their pools over less than 1 time per day and have crystal clear sparkling water. I recall some people that are running their pumps for no more than 4 hours each day with no issues.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[SPP]

Hi J,
Thanks for the reply. I am interested to know technically will the water move or not in such a set up and flow, that is all.
As to achieving clarity I am very good with it already and know my pool well, so no issue.
Speed of getting best clarity and the experimentation of such set up is what I am after....he he he

 

[chem geek]

The following are the percentages of water passed through the circulation system (including the filter) for the number of turnovers indicated assuming perfect mixing in the pool (which of course doesn't happen):

1 turnover: 63.2%
2 turnovers: 86.5%
3 turnovers: 95.0%
4 turnovers: 98.2%
5 turnovers: 99.3%
6 turnovers: 99.75%
7 turnovers: 99.91%
8 turnovers: 99.966%
9 turnovers: 99.988%
10 turnovers: 99.995%

You never get to 100% and again, the above assumes perfect near instantaneous mixing in the bulk pool water.

 

[SPP]

Hi Chem,

Yes that data looks Dang good. I needed 11x turnover with no bather load, just ambient airborne dust , to get back my maximum clarity during my 50% water change.

This is the exact reason I was doing some day dreaming if moving water the way I imagined, will make a 2x turnover my dream version as efficient as say a 7-8 times turnover on conventional pool plumbing. The impossible way of actually getting all "old" water filtered is what made recovery so slow and power consumption so high isn't it ?

Thanks
.

 

[chem geek]

So for what you want to do you want to introduce water at one end of the pool and remove it from the other end and try to "move it" as you say so that it doesn't mix as much. That isn't easy to do and if you were successful it would probably be a significantly strong current which isn't a good side effect unless you intended this to be an "endless pool".

 

[East_Akl_Neil]

I cant help thinking that any potential savings made in reducing runtime would be way less than the costs of all the plumbing, filters and pumps to run it all.

The other thing is why is a setup like this not 'the norm', I guess that comes back to cost.

I do like the theory tho.

 

[SPP]

Hi Chem & Neil,

Yes, something like endless pool but not that fast waterflow. This is not about swimming practice, this is about getting best clarity fast. US$$20,000 for extra 14 pumps and cartridge filters and plumbing is nothing compare to the overall pool cost and pleasure of needing only 2 hours for maximum clarity, assuming it will work

Like my friend who owns a 25 meter pool, he wants a 50 meter pool next time when space allows and he does not want the 4.7 hours per turnover as he has now, to him that is too slow when his kids has lots of friends. He has seen his peak water clarity and he realized it takes lots of money to stay clear fast and he is willing to do so. Its addictive being able to get best clarity, it shows the proper way of pool care is possible when one is willing to spend more $$ and time and listened to an alumni of TPF . He tried an indoor pool in Japan and he said not only the clarity is superb ( better than his pool ) the comfort of water is the best he ever tasted in his mouth. No that he drinks it but its the same as putting Evian in his mouth.......that good he said.

So its kind of fun when my boss wants to build a 20 meter pool, if I can experiment 1 hr turnover and trying to move the water. Regardless it works or not the moving water theory, having 1 hour turnover is simply great.

If I were to make a new pool, most unlikely though, I will make it have the system to do 1 hour turnover.
The pump and the filter cartridge based on Pentair 50HZ version ( lower power than 60HZ ) 0.75HP is only US$1,100 local price. 14 of those and extra plumbing will make it US$20K. I can make a few filter towers that can house something like slime bag or anything with 1 micron capability but not using DE as secondary filter downstream of the cartridge ones. Slime bag does work, its proven, it is so cheap at US$50 a piece, all I got to do is make a filter tower for it.

I now have access to very powerful ozon generators at low cost. 1/3 or less than what USA makers are pricing it.
I probably inject ozone to German DIN standard so that chloride level and whatever TDS from chlorine will not raise so much in a year by using less chlorine if I can. This is all about personal satisfaction and extra $$ can be justified.

You know.........one funny thing. My friend's 225 M3 pool was designed with 1.5HP x 2 pumps 50hz version. Pool builder calculated it to be within 8 hours per turnover but when I installed flow meters, it was 12 hours per turnover due to :

01. Pump room is minus 4 meters below pool's water surface. To look good the pump room is underground but one pay lots of pressure loss. His two sand filters, both have cracked ( Australian brand ), due to the massive pressure caused by -4 meters and and additional cartridge filter downstream of the sand filter ( zeolite for sand ). I had to add air cooling blowers to remove the heat of all the pumps running.

02. Pool inlet overall height is not the same towards impeller because the pool is part in ground and part above ground. So some flows water well and some don't. Surely distance wise no inlet is the same distance to the pump too, adding the misery of not able to achieve similar output per water inlet nozzle.

03. Simply too optimistic calculation because none of the builder installations ever has a flowmeter installed, so he never actually learned the truth.

So finally, I had to use the allocated 1.5HP vacuum robot pump as filter pump by adding a slime bag only at output. Clarity improved and recovery was faster as 12 hours per turnover have dropped to approx 8 hours.

As time goes by, my friend expectation gets higher. He wanted to see clearly end to end of the 25 meters pool and he knew he can do that when pool at peak clarity when low bather load. So he asked me, how could he achieve that clarity consistently while in use and/or faster speed of recovery ? I said add another pump. So he did, another 1.5HP pump using cardtridge filter and 1 slime bag at output.

Now his pool is at approx 4.7 hours per turnover and that needs 6 HP pumps and none is ever off, all run 24/7 whole year.
His electrical bill for the pool is a lot but he knew there is no other choice. The concrete pool building cost is any easy US$200K, so, like any Ferrari owner, play hard and pay plenty.

I don't know about most people who own pools, but for me and my friend, who is already addicted to very clear water, there is no going back. Since we both are divers, we wear mask for inspection of water clarity and that is one tough test. Pool swimmers goggle have distortion, diver mask are glass and great lens quality and 25% magnification due to refraction and we see so much better.

The other facts which speak for himself is a comment from his swimming instructor who serves very wide clients base and have access to many private pools or 5 star hotel pools. The best pool water in terms of comfort is my friend's pool, that is what the instructor said. His instructor been teaching my friend and his kids for two years and the schedule is once a week. So at least close to 100 pool sessions as comparison. The same comment I get for my pool from dive students, which are plenty of them a year. Even my son and daughter does not want to swim in public pools anymore. They understood of chloramine smell and water balance. When their eyes get that uncomfortable sensation, they knew its not like Daddy's pool

Experimenting with my boss pool is the kick I am getting now.
I am naturally an itch handed person and like to experiment.........ha ha ha.

Thanks Guys.
SP

 

[chem geek]

If you do the flow end-to-end (rather than side-to-side) and it's a 50 meter long pool with a 1-hour turnover rate, then that's about a 1/2" per second water flow. You'd want very broad returns, not eyelets, to produce an even smooth flow and likewise for the drains on the wall at the other end. However, it's not at all clear that the water won't form channels with that long distance such that there will be dead spots unless you have additional returns on a diagonal along the sides.

A completely different approach would be a flow from one side to the other. To minimize the feeling of getting "pushed" during swimming, you would want broad returns (not eyelets) and would want something similar for the drains and gutter on the other side. Assuming cost is no object, it's a "wall-of-water" project. The velocity of water in the pool would be less side-to-side in proportion to the width vs. length.

If the pool is not shallow, then consider that most of the contaminants are introduced from bathers (or from things dropping in from the air in an outdoor pool) so the water near the surface is generally dirtier than that at depth unless it's particulate matter that settles.

 

[mas985]

I am always game for a good thought experiment although this one seems have a few OCD underpinnings that might be better served on a therapist's couch than on a pool forum.

But I agree with Richard, lowering the water velocity will reduce the mixing of the water and thus filter more of the water in the same amount of time. I use this technique when I need to replace water in the pool so I drain the pool but replace the water while at the same time removing it from the other end of the pool. I can get water replacement rates well above 90% but I am only replacing about half the water.

Also, a few comments on the pumps. For a given flow rate, you are far better off using fewer larger HP pumps than many more smaller HP pumps. Power efficiency of the motors and wet ends tend to go up with larger pumps so for a given flow rate, less energy will be used with the larger the pump. Of course you need the plumbing to support the high flow rates as well.

 

[chiefwej]

Most anything that you are trying to filter out is either heavier than water or lighter than water. So it all sinks or floats. That is the reason that pools have skimmers and bottom drains to draw water from the top and bottom of the pool. Water clarity can be more a result of the type and effectiveness of your filter than turnover rate. Low speed pumps don't have a very high turnover, but when combined with a good Highly effective DE filter can result in amazing water clarity.

If you aren't returning highly filtered water, turnover rate means very little.

 

[SPP]

Most anything that you are trying to filter out is either heavier than water or lighter than water. So it all sinks or floats. That is the reason that pools have skimmers and bottom drains to draw water from the pool. Water clarity can be more a result of the type and effectiveness of your filter than turnover rate. Low speed pumps don't have a very high turnover, but when combined with a good Highly effective DE filter can result in amazing water clarity.

If you aren't returning highly filtered water, turnover rate means very little.

Hi Chem,
My boss pool will be 20 meters most likely and 4.5 meters wide.
If say I do side to side water flow, based on 14 pumps ( to get that 1 hr turnover ) wont there be more potential of old water mixing with new one ?.
I mean pushing 20 meter wide water against 4.5 meters wide, won't pushing a 4.5 meter wide water be easier ? If I were to do the long 20 meters end to end, surely I will not install that small nozzle aiming balls for the inlet. I will just open up the whole 2 inch pipe. Channeling is a possibility, yes possible.

Perhaps I must do scale test.........he he he. I know how pool builder make theme park for moving water, the looped pool one, but there is still old water and filtered water being mixed right ?


Mas,
What is an OCD ?

But I agree with Richard, lowering the water velocity will reduce the mixing of the water and thus filter more of the water in the same amount of time. I use this technique when I need to replace water in the pool so I drain the pool but replace the water while at the same time removing it from the other end of the pool. I can get water replacement rates well above 90% but I am only replacing about half the water.

Yes, that does sounds good , thanks.


Also, a few comments on the pumps. For a given flow rate, you are far better off using fewer larger HP pumps than many more smaller HP pumps. Power efficiency of the motors and wet ends tend to go up with larger pumps so for a given flow rate, less energy will be used with the larger the pump. Of course you need the plumbing to support the high flow rates as well.

OK me will check the much bigger HP ones. 1.5 vs 1.0 vs 0.75 HP as per Pentair data sheet, I get better efficiency with 0.75 as long as I don't make the head above 15psi. I suppose if I get a slower rpm pump, a big one, the efficiency goes up yah ?

[attachment=0:1303t93y]Pump curve 50hz.JPG[/attachment:1303t93y]

I can't tell of the electrical demand between the 0.75HP vs the 1.5HP when each at 15 psi head but the flow favors the 0.75HP as per the chart based on purchase of pumps quantity. That is why I choose 0.75HP.

Thanks Gents.
.

 

[SPP]

Most anything that you are trying to filter out is either heavier than water or lighter than water. So it all sinks or floats. That is the reason that pools have skimmers and bottom drains to draw water from the top and bottom of the pool. Water clarity can be more a result of the type and effectiveness of your filter than turnover rate. Low speed pumps don't have a very high turnover, but when combined with a good Highly effective DE filter can result in amazing water clarity.

If you aren't returning highly filtered water, turnover rate means very little.

Hi Chief,
DE is what I never tried. Its hard to buy the maintenance stuff in my country for DE. I asked before and I don't like making "cakes" on the drain from DE, one complaint I heard.......is that true ?

I can go water treatment route with 1 micron cartridge filters. I will take a look at DE real beta ratio against other types and see how. The last time I checked I can't get DE filter beta ratio and that is one value I must know. Sand for sure even with zeolite has very low beta ratio.... I don't like it, must add cartridge downstream of it.

If the DE can catch super small algae like the slime bag, I will be most happy, otherwise its not fine enough. No matter how clear my water is, the super small baby algae are always trapped by the slime bag.

If you are using DE and have those waterproof camera, can you please take underwater photo from pool end to pool end while at best clarity for me to see what DE can deliver in a cleaner environment like yours ? My city airborne dust dirt is so bad . Or if you have turbidity test using NTU value, I am dying to see it, that so happened is the only data I have with me to relate to my filter performance.

Many thanks Chief.

.

 

[SPP]

Chief,
I forgot to tell you. Drains on pool bottom is not effective to get dirt based on suction alone for a wide area pool. Overflow is effective to get the top dirty water direct to gutter, yes. I clean my pool with scuba tanks, vacuum hose on left hand and a brush on my right hand once in a while. Daily vacuuming the pool bottom is not bad and is done everyday by my pool boy.

Ur 2 HP pump x 2 for a 19K gallon pool is big...nice !!...... if all dedicated for filtration and none for massage or whatever water features u got.
Are those 4 HP total all goes thru the DE ? Looks like ur pool can do <4 hours turnover yah ? Dang so sweet.

Thanks
.

 

[mas985]

OCD - Obsessive Compulsive Disorder

Anyway, the pump curve that you are showing is for the Optflo above ground pump which I would not recommend for this application because you will never get them to prime unless they are below water level.

OK me will check the much bigger HP ones. 1.5 vs 1.0 vs 0.75 HP as per Pentair data sheet, I get better efficiency with 0.75 as long as I don't make the head above 15psi.

It depends on what you are assuming for the plumbing system. Smaller pumps can be more efficient only if they are put on independent plumbing systems so their head is not additive. If you retrofit an existing pool, this may not be the case so a few larger pumps may end up being more efficient.

When pumps are placed in parallel so they share common plumbing, the head is additive because the plumbing head loss is dependent on the flow rate of all pumps together and this reduces the efficiency of each pump. However, if they are plumbed on independent plumbing loops, then their efficiency is maintained and they no longer interact.

But if money is no object, I would get twice the number pumps in two speed form and run them all on low speed. But again, they would each need its own plumbing loop to maintain efficiency.

 

[East_Akl_Neil]

This is all sounding like some serious cases of "Sparkly Poolits" is going on here....

 

[chiefwej]

Chief,
I forgot to tell you. Drains on pool bottom is not effective to get dirt based on suction alone for a wide area pool. Overflow is effective to get the top dirty water direct to gutter, yes. I clean my pool with scuba tanks, vacuum hose on left hand and a brush on my right hand once in a while. Daily vacuuming the pool bottom is not bad and is done everyday by my pool boy.

Ur 2 HP pump x 2 for a 19K gallon pool is big...nice !!...... if all dedicated for filtration and none for massage or whatever water features u got.
Are those 4 HP total all goes thru the DE ? Looks like ur pool can do <4 hours turnover yah ? Dang so sweet.

Thanks
.

Only one of my pumps is for filtration, the other is dedicated to the spa. For filtration I have a DE filter but I use cellulose fiber media. If you have a high turnover but use a filter that only filters to 30 microns like sand, the water won't be as clear as a lower turnover with a DE (or cellulose media) that filters to 3 microns. We have lots of dust and dirt here in the desert. I typically run my filtration around 6 hrs/day and the water stays quite clear. Of course I have 3700 ppm salt and 50 ppm borates which seems to add some extra sparkle to the pool.

 

[SPP]

Ok Chief, got that. Thanks

My Pump 1
My sand with zeolite can do 3 microns but at very poor beta ratio
Downstream of my sand, I have 20 micron filter cartridge, not too bad

My Pump 2
Cartridge 20 micron >>>>Slime bag 1 micron with unknown beta ratio but proven to work well

Later,