UV Sterilizers, pumps, filters and Pressure side Pressure: Too High

[mas985]

BTW, the spreadsheets in my signature can estimate your pump's flow rate without having to buy a flow meter.

 

[Yurij]

BTW, the spreadsheets in my signature can estimate your pump's flow rate without having to buy a flow meter.

Yes, for a SWAG or baseline I think it's great. But in reality there could be a difference. Ie. The UV sterilizer impact to head loss and other equipment that impact head loss.. I'll let you know how things work out. Most head loss and GPM curves based on pump HP show a small difference in head loss could have a reasonable impact to GPM and turn over. Think about it, Friction and work are variables here not to be ignored. My next season project is almost defined.

 

[mas985]

Yes, for a SWAG I think it's great. But in reality there could be a difference. Ie. The UV sterilizer impact to head loss and other equipment that impact head loss.. I'll let you know how things work out. I like it! My next season project is almost defined.

The spreadsheet takes all of that into account. The filter pressure is used as one data point which includes all head loss from that point forward to the pool. The rest can either be modeled or directly measured with a suction gauge. These techniques have been proven to be fairly accurate (<5% error).

Just keep in mind that Blue White flow gauges are not very accurate (10% at best). If you want something more accurate, get a FloVis.

 

[Dirk]

By the way, I noticed most on this site prefer SWG systems and not much content on UV systems. Would be interesting to get some unbiased opinions of the pros and cons of each and compare.

It's not really opinions, there's science to back it up. At least, that's my opinion! Here's my take. UV systems do a fine job of stripping your water of the nasties you don't want in and on your body. But they only do that for the water that is actually inside the tank. Your model makes claims that it can treat a pool up to 50K gallons, and that might be true, IF (big if) the pool was completely isolated and nobody swam in it! Once the water leaves the tank, your UV system provides no protection from nasties out in the pool, where you are. There is no residual protection. And the sterilizing you think it is doing assumes every cubic inch of your water passes through it. Once back in the pool, the processed water doesn't magically sterilize all the other water (though technically it dilutes it to a small degree). What do you think the chances are that your circulation system is so good that all your water passes through your UV system often enough to protect you enough? The answer is zero chances, and here's why. Your water can take on pathogens at any moment. A bird flying over. An animal drowning during the night. Bugs. Run off. Etc. And all humans introduce nasties, the minute they get in, even if they aren't sick (don't make me explain that!), and even more if they are sick. How much time must pass between those "introductions" and when those germs are going to get sucked into your UV system? Meanwhile, you and your guests are swimming around in that stew.

That's why there has to be the same amount of chlorine in a UV pool as there must be in one without UV. Chlorine provides that residual protection. It's everywhere, all the time, in every corner or crevice, in every cubic inch, and it goes to work instantly on any junk it touches, not some number of minutes or hours or days later. You've gotten the impression that you can use less chlorine. I'm pretty sure that is not true. Maybe a tiny bit less, as the UV is doing a small amount of the sanitization. But not in the way you are thinking.

Now UV does provide benefit to your pool. But that is more than covered by the sun (no flow problems there!). If your pool was in constant shade, or indoors, that might justify a UV boost. It's why we tell folks that they have to uncover their pools every day or two to allow the sun's UV to do it's thing. But if your pool is in the sun some part of the day, it's already getting all the UV it needs.

I'll let someone else chime in about the Frog system, as I don't know much about that, other than it introduces metals as part of its process, and they will eventually wind up as stains on your finish. Something like that.

I had to tear a couple of components out of my system when I first came on board here. A lot of us did. Pool builders don't know this stuff, or do, and sell us these "solutions" anyway, because there is good profit in those products. I understand that some of these types of product manufacturers incentivise PBs to do the install, because they know they'll get that back in parts sales (your UV bulb, for example). Sorry, that's the reality of the industry.

Like I said, if you want to solve your flow problem, bypass the UV. You have to put the same amount of chlorine in your pool anyway. I get why you might not want all the salt of an SWG, but you'll find the general opinion here is that that amount of salt does not cause the problems that PBs and Pool Stores want you to believe. Or there are chlorine injection systems (Stenner) that work to save you some effort on liquid chlorine use. Might be worth a look before you buy that second UV. That's where you can gather opinions, between SWG and injection. Lots of pros and cons to those to systems. But UV systems are not in the running. As Pat mentioned in his post #15, you can do a search of the forum and you'll find tons of threads debating between SWG and Stenner.

Good luck with whatever you decide.

 

[Flying Tivo]

My next season project is almost defined.

I was just like you in my younger years, life has kicked me in the butt a few times and now i dont overthink things much. Rather be floating in the pool with a cold one and enjoying every last minute of Sunshine on my face. You have not asked me but my opinion is to keep a good control on chems and a Good CSI index so your heater is safe(this is what has you most worried). Ph is the most important for this index and your heater. As for energy, you pay the bill, so play with flows as much as you want. I run my pump at 1200rpms@89watts with filter presures at 1-2psi for just 2 hours a day.
Proof is in the pudding:

 

[Yurij]

It's not really opinions, there's science to back it up. At least, that's my opinion! Here's my take. UV systems do a fine job of stripping your water of the nasties you don't want in and on your body. But they only do that for the water that is actually inside the tank. Your model makes claims that it can treat a pool up to 50K gallons, and that might be true, IF (big if) the pool was completely isolated and nobody swam in it! Once the water leaves the tank, your UV system provides no protection from nasties out in the pool, where you are. There is no residual protection. And the sterilizing you think it is doing assumes every cubic inch of your water passes through it. Once back in the pool, the processed water doesn't magically sterilize all the other water (though technically it dilutes it to a small degree). What do you think the chances are that your circulation system is so good that all your water passes through your UV system often enough to protect you enough? The answer is zero chances, and here's why. Your water can take on pathogens at any moment. A bird flying over. An animal drowning during the night. Bugs. Run off. Etc. And all humans introduce nasties, the minute they get in, even if they aren't sick (don't make me explain that!), and even more if they are sick. How much time must pass between those "introductions" and when those germs are going to get sucked into your UV system? Meanwhile, you and your guests are swimming around in that stew.

That's why there has to be the same amount of chlorine in a UV pool as there must be in one without UV. Chlorine provides that residual protection. It's everywhere, all the time, in every corner or crevice, in every cubic inch, and it goes to work instantly on any junk it touches, not some number of minutes or hours or days later. You've gotten the impression that you can use less chlorine. I'm pretty sure that is not true. Maybe a tiny bit less, as the UV is doing a small amount of the sanitization. But not in the way you are thinking.

Now UV does provide benefit to your pool. But that is more than covered by the sun (no flow problems there!). If your pool was in constant shade, or indoors, that might justify a UV boost. It's why we tell folks that they have to uncover their pools every day or two to allow the sun's UV to do it's thing. But if your pool is in the sun some part of the day, it's already getting all the UV it needs.

I'll let someone else chime in about the Frog system, as I don't know much about that, other than it introduces metals as part of its process, and they will eventually wind up as stains on your finish. Something like that.

I had to tear a couple of components out of my system when I first came on board here. A lot of us did. Pool builders don't know this stuff, or do, and sell it anyway, because there is good profit in those products. I understand that some of these types of product manufacturers incentivise PBs to do the install, because they know they'll get that back in parts sales (your UV bulb, for example). Sorry, that's the reality of the industry.

Like I said, if you want to solve your flow problem, bypass the UV. You have to put the same amount of chlorine in your pool anyway. I get why you might not want all the salt of an SWG, but you'll find the general opinion here is that that amount of salt does not cause the problems that PBs and Pool Stores want you to believe. Or there are chlorine injection systems (Stenner) that work to save you some effort on liquid chlorine use. Might be worth a look before you buy that second UV. That's where you can gather opinions, between SWG and injection. Lots of pros and cons to those to systems. But UV systems are not in the running.

Good luck with whatever you decide.

You bring up some good points. As far a nasties in the pool, obviously a UV sterilizer will not eliminate algae that is secured to the liner and not able to pass through the sterilizer. That's why we need chlorine supplements, otherwise having a sterilizer is a waste of money. You need to supplement with chlorine. As far as Ozone contributed by sun light? Yes this happens. But sunlight also is an incubator for algal blooms. That's an established fact of nature. In my case, I decided not to go with an ozonator for the same reason not to go with a SWG. Unless you have perfect water chemistry SWG systems cause corrosion to things like heaters. They can clog up and become not useful. So I guess it depends on your requirements and goals. Both SWG and UV systems need chlorine. My requirement is to also preserve the heater. BOth solutions minimize the amount of chlorine sanitizer needed to maintain your pool. SWG creates it's own chlorine source and UV require you to supplement with Chlorine. Same results, just different methods. Note: Public pool systems running on SWG require to have a chlorine back up in case the SWG cannot generate enough chlorine to do the job. Also, SWG systems do recommend occasional shock as needed to keep things balanced. There is a reason for this. I understand science, chemistry and physics very well!

 

[Yurij]

You bring up some good points. As far a nasties in the pool, obviously a UV sterilizer will not eliminate algae that is secured to the liner and not able to pass through the sterilizer. That's why we need chlorine supplements, otherwise having a sterilizer is a waste of money. You need to supplement with chlorine. As far as Ozone contributed by sun light? Yes this happens. But sunlight also is an incubator for algal blooms. That's an established fact of nature. In my case, I decided not to go with an ozonator for the same reason not to go with a SWG. Unless you have perfect water chemistry SWG systems cause corrosion to things like heaters. They can clog up and become not useful. So I guess it depends on your requirements and goals. Both SWG and UV systems need chlorine. My requirement is to also preserve the heater. BOth solutions minimize the amount of chlorine sanitizer needed to maintain your pool. SWG creates it's own chlorine source and UV require you to supplement with Chlorine. Same results, just different methods. Note: Public pool systems running on SWG require to have a chlorine back up in case the SWG cannot generate enough chlorine to do the job. Also, SWG systems do recommend occasional shock as needed to keep things balanced. To your point about finding a dead animal in my pool, It's happened. The first thing I do is shock the pool very well when this happens. Regardless of whether the UV sterilizer is running well. I would do this regardless if I were running a UV system or SWG. There is a reason for this. I understand science, chemistry and physics very well!

 

[Yurij]

I was just like you in my younger years, life has kicked me in the butt a few times and now i dont overthink things much. Rather be floating in the pool with a cold one and enjoying every last minute of Sunshine on my face. You have not asked me but my opinion is to keep a good control on chems and a Good CSI index so your heater is safe(this is what has you most worried). Ph is the most important for this index and your heater. As for energy, you pay the bill, so play with flows as much as you want. I run my pump at 1200rpms@89watts with filter presures at 1-2psi for just 2 hours a day.
Proof is in the pudding:

View attachment 158914

I hear you, Since installing the Eco Pump my energy costs have decreased at least 50% compared to running a pump full force 100% of the time. My current cost $200/season or $40/month for electricity. Some people still run low efficency and high cost pumps as you probably know. I am an Engineer and not as young as you think. No skin off my back and far from over analyzing. Bottom line, I spend about one hour a week maintaining my pool and it looks very similar to yours. I probably run my pump at full power longer than needed. This is because of heating and running another pump to allow my Polaris 3900 to complete pool cleaning. You have to just love and respect wisdom!

 

[Dirk]

Uh, you missed a couple things, I think. The chlorine will work on stuck-on algae where UV won't, yes. But I was describing pathogens floating around in the water. Algae is relatively harmless to humans, but those pathogens are not. Chlorine kills those almost instantly. UV systems may, OR MAY NOT, do that, as those pathogens may, OR MAY NOT, ever end up in the chamber. But even if they do, it won't be instantly. So the chlorine you're "supplementing" with is not just for stuck on stuff, it's for the entire body of water. And if you have to use chlorine to protect yourself (which we know you do), why are you using UV? One could say, "It's not hurting anything, and adding some benefit, so what's the harm?" except in your case it is hurting something, your flow. For no measurable benefit. Your trying to solve a problem that doesn't need to exist, is my over-arching theme.

And please allow me to correct your statement "SWG systems do recommend occasional shock." That is not true at all. I've never shocked my pool, and/or had to perform a SLAM. Shocking is a Pool Store term and scare tactic to get people to buy their shock products. Nothing more. It's more than possible that with a properly functioning SWG you would never need to add any additional chlorine, let alone shock (which, I think, is just chlorine, don't know, never bought any). SWG pools do not require shocking as any part of a regular, normal maintenance regime. At any interval. Now, any pool is subject to abnormal conditions that might require additional sanitation to control (dead animal, bather load, extreme heat, etc) but that would occur in any pool with any sanitizing system, and has nothing to do with the use of an SWG.

And sorry, I didn't mean to dump on you and your choice of sanitation, nor mean to put you into a position of having to defend that choice. I just know I wouldn't want to swim in a UV only pool, and would be cautious about a UV+chlorine pool unless I knew the owner understood the principles I've described. But that's for each pool owner and swimmer to decide for themselves.

Thanks for being so gracious about our discussion.

 

[Yurij]

Uh, you missed a couple things, I think. The chlorine will work on stuck-on algae where UV won't, yes. But I was describing pathogens floating around in the water. Algae is relatively harmless to humans, but those pathogens are not. Chlorine kills those almost instantly. UV systems may, OR MAY NOT, do that, as those pathogens may, OR MAY NOT, ever end up in the chamber. But even if they do, it won't be instantly. So the chlorine you're "supplementing" with is not just for stuck on stuff, it's for the entire body of water. And if you have to use chlorine to protect yourself (which we know you do), why are you using UV? One could say, "It's not hurting anything, and adding some benefit, so what's the harm?" except in your case it is hurting something, your flow. For no measurable benefit. Your trying to solve a problem that doesn't need to exist, is my over-arching theme.

And please allow me to correct your statement "SWG systems do recommend occasional shock." That is not true at all. I've never shocked my pool, and/or had to perform a SLAM. Shocking is a Pool Store term and scare tactic to get people to buy their shock products. Nothing more. It's more than possible that with a properly functioning SWG you would never need to add any additional chlorine, let alone shock (which, I think, is just chlorine, don't know, never bought any). SWG pools do not require shocking as any part of a regular, normal maintenance regime. At any interval. Now, any pool is subject to abnormal conditions that might require additional chlorine to control (dead animal, bather load, extreme heat, etc) but that would occur in any pool with any sanitizing system, and has nothing to do with the use of an SWG.

And sorry, I didn't mean to dump on you and your choice of sanitation, nor mean to put you into a position of having to defend that choice. I just know I wouldn't want to swim in a UV only pool, and would be cautious about a UV+chlorine pool unless I knew the owner understood the principles I've described. But that's for each pool owner and swimmer to decide for themselves.

Thanks for being so gracious about our discussion.

No worries, I'm here for fun and to learn. Currently, with respect to end results, I see very little difference between SWG and UV in terms of results. I have a close friend who runs a SWG and he shared some pros and cons with me based on his experience. At the end of our conversation we reached consensus that both systems produce similar results, and from a cost perspective, very little difference. He ended up having to clean out his SWG because of mineral deposits which threw the unit off. I hope this doesn't offend anyone here. I agree the UV threw me a curve in terms of the pressure issue and appreciate confirmation that it's all about the UV unit. I'll throw in the flow meter, do some calculations, read the articles, and tweak away. This is not a major project and just a fun hobby. Will post results. Be well and thanks for the conversation. Dirk, I read a lot about SWG systems and not everyone is in agreement using shock is not recommended. Please refer to public pool policies and mandatory rules in place to have a back up chlorination system if the SWG fails to maintain proper ORP levels. I believe you, but these safe guards are in place due to issues with SWG systems to keep levels to acceptable standards. This does not make SWG systems a bad choice, but something to keep in mind.

 

[Newdude]

Unless you have perfect water chemistry SWG systems cause corrosion to things like heaters

Having water within range is a snap the TFP way. Using the pool store, its darn near impossible.

Also, SWG systems do recommend occasional shock as needed to keep things balanced

The manufacturer knows about building my equipment. They are not experts in how to manage my water after the fact. They follow the government guidelines enacted in the 70s. Yes, the 1970s. Imagine going to the Dr today like it was 1970. The government did not evolve with the times and likewise neither has the pool industry. Thank goodness Healthcare did !! In 8 years I never needed to shock my salt pool. 6.5 of those were pre TFP so I was ignorant to proper (and easy) chemistry and STILL never had a need to shock because the SWG kept my FC exactly where it needed to be.

 

[Yurij]

Having water within range is a snap the TFP way. Using the pool store, its darn near impossible.

The manufacturer knows about building my equipment. They are not experts in how to manage my water after the fact. They follow the government guidelines enacted in the 70s. Yes, the 1970s. Imagine going to the Dr today like it was 1970. The government did not evolve with the times and likewise neither has the pool industry. Thank goodness Healthcare did !! In 8 years I never needed to shock my salt pool. 6.5 of those were pre TFP so I was ignorant to proper (and easy) chemistry and STILL never had a need to shock because the SWG kept my FC exactly where it needed to be.

SWG systems do not walk on water and are not perfect. Neither are UV sanitizers. It's about weighing out the pros and cons and selecting based on your individual requirements. I'm happy to hear you have had success with SWG and never had to shock. Honestly, I don't think you can say no one ever needed to shock a SWG system. That would be completely unrealistic and a waste of time to debate. I think it's time to move on to another discussion. I'll work on the pressure issue now. Respectfully

 

[Dirk]

No offense, at all! If you follow TFP guidelines, you can avoid the build up on the SWG plates. That has worked for me. And my thoughts are based mostly on my direct experience with only one pool, mine. I think it is safe to say (I'll be corrected, otherwise), that TFP methods and our teachings about them are geared to residential pools, and outside residential pools at that. Not exclusively, but primarily. Indoor pools and public pools are a different beast. Government jurisdictions that involve themselves in pool care have a different set of guidlelines that make using TFP methods prohibitive. (I think that's what Newdude was saying.)

Edit: Oops, we were writing at the same time. Roger that, moving on. Cheers.

 

[mas985]

Both SWG and UV systems need chlorine.

SWGs don't need supplemental chlorine, they generate the chlorine from the salt.

Also, there is one large difference between SWGs/chlorine systems and UV systems. Chlorine residuals. SWGs/chlorine residuals kill bacteria and algae even while the pump is off. UV systems can only do that as water passes through the cell. So it will take many days before all the water passes through the UV system. That is far too long to wait for a pathogen to be killed. With chlorine residuals, the kill time is in seconds, not days. So if you are reliant on chlorine anyway, of what use is the UV system? TFP only recommends UV systems for indoor pools where there is no UV to break down combined chlorine. That is really their only use.

 

[Yurij]

SWGs don't need supplemental chlorine, they generate the chlorine from the salt.

Also, there is one large difference between SWGs/chlorine systems and UV systems. Chlorine residuals. SWGs/chlorine residuals kill bacteria and algae even while the pump is off. UV systems can only do that as water passes through the cell. So it will take many days before all the water passes through the UV system. That is far too long to wait for a pathogen to be killed. With chlorine residuals, the kill time is in seconds, not days. So if you are reliant on chlorine anyway, of what use is the UV system? TFP only recommends UV systems for indoor pools where there is no UV to break down combined chlorine. That is really their only use.

As mentioned, prior to installing the UV I had an occasional bout with algae with my current system. The UV sanitizer is sized to kills pathogens in the water with every cycle. After installing the UV, there has been a noticable difference in water quality and clarity. Not even cloudy water. This is no coincidence. TFP is not a definitive source of pool maintenance, although very respectable source of information. As mentioned in another post, if you think SWG walks on water, that's fine, but it's simply not true. I'm glad it works for you, and I almost purchased a SWG. Again, it's a matter of weighing out the pros and cons. I have similar results with the UV as SWG systems. For that matter, probably no different than just using plain old chlorine for sanitizing. From what I hear SWGs are great systems. I am not trying to say UVs are any better than SWGs. Just sharing experience. Time to move on. This thread is about Pressure issues, which I acqknowledge is caused by the UV sanitizer. That's a con, but fixable.

 

[Flying Tivo]

There is a reason for this. I understand science, chemistry and physics very well!

Many have walked this path, we are not here to shove or push, but, after you lurk and read enough in this forum you will come to your own conclusion(as i did) about specific Pool water chemistry, not chemistry in general. We have figured out the ROI on SWG on this forum and is mostly equivalent to purchasing liquid chlorine in advance. Dont know about ROI of UV lamps, maybe you can help us.

 

[mas985]

As mentioned, prior to installing the UV I had an occasional bout with algae with my current system.

If you were following TFP methods, that would not be the case.

The UV sanitizer is sized to kills pathogens in the water with every cycle.

It kills some of the pathogens in the water. Each turnover passes only 65% of the water through the system. To get a 99.5% kill, it takes 5 turnovers. If your pump is running at 30 GPM, a turnover is 17.8 hours so it would take close to 90 hours. A fast kill is a safer pool.

 

[Yurij]

If you were following TFP methods, that would not be the case.

It kills some of the pathogens in the water. Each turnover passes only 65% of the water through the system. To get a 99.5% kill, it takes 5 turnovers. If your pump is running at 30 GPM, a turnover is 17.8 hours so it would take close to 90 hours. A fast kill is a safer pool.

I respectfully disagree but will not debate a few hours of difference. Pushing subjective opinions is a waste of time. That's why I like real data, which you haven't presented. This is my last post on the topic. Respectfully

 

[Yurij]

I respectfully disagree but will not debate a few hours of difference. Pushing subjective opinions is a waste of time. That's why I like real data, which you haven't presented. Reputable data reference please? Otherwise I can't take the comment seriously. This is my last post on the topic. back to the original objective of this thread. Respectfully

 

[mas985]

What are you disagreeing with and what data would like? The forum has lots of data that supports all of these concepts.

If you are referring to the law of dilution, that is here:

CPO Training - Further Reading

www.troublefreepool.com

and here:

Law of dilution - Wikipedia

en.wikipedia.org

Also, Pool School has all the evidence anyone should possibly need.