Criteria for upgrading filter

[deenamccauley]

What criteria should be included when looking at upgrading a filtration system?
I'm getting lots of mixed messages on whether we need to upgrade so I'm just wondering what the pool pro's here would look at as indicators of a need for increased/upgraded filtration.
Thanks

 

[mas985]

Big.

Ok so I assume you want a bit more detail but you really want to oversize your filter. Make sure it can handle at least the flow rate of your pump at low head loss and even then I would oversize that by at least 20%.

Other than that it is a matter of prefrence between, DE, Cartridge and Sand.

 

[duraleigh]

Deena,

Your question begs more questions. What does your current system consist of? How big is your pool? Have you had any past issues with pool circulation? Tell us a little more about what currently exists and we'll be able to submit some opinions.

 

[deenamccauley]

Deena,

Your question begs more questions. What does your current system consist of? How big is your pool? Have you had any past issues with pool circulation? Tell us a little more about what currently exists and we'll be able to submit some opinions.

My pool is 120,000 litres. I have a 26inch Fox Meteor High Rate Sand filter. Max flow rate on that is 70 gpm
Pump: Centerian 2 speed Switchless Motor 1.5/.25 HP

This past summer our bather load increased alot so we had issues with cloudy water. Also very short filter runs, we were backwashing at least once a day, often 2 or 3 times a day. We also had issues with bacteria for the last bit of the summer.

So we are looking at whether or not we need to add a supplimental filtering system or whether we are just doing something wrong.
Thanks for your help

 

[JasonLion]

120,000 liters is about 31,700 gallons. At the max rate for the filter of 70 gpm that would be 453 minutes to turn over the water, or about 7 1/2 hours. It is likely that running the pump on high speed doesn't actually move 70 gpm (though it might) so the actual turn over would probably be somewhat longer. Assuming your setup is fairly standard, I would guess that turnover is actually somewhere between 8 and 12 hours. All of that is normal for a residential pool and about what we might recommend (though we would suggest a slightly larger filter).

A commercial pool would typically aim for a four to six hour turnover (or faster in some cases). That would require a substantially larger filter, larger pump, and probably larger pipes as well (depending on what you have now).

A typical residential pool might support an average of 2 to 6 people swimming a day. I know that when we have a pool party, perhaps 20 people in the water over the course of the day, it takes a couple of days for the filter to catch up. If you had 20 people every day I could well imagine there would be problems. Still, you mentioned needing to backwash more than once a day, which doesn't seem plausible if the system was working properly.

 

[JohnT]

This past summer our bather load increased alot so we had issues with cloudy water. Also very short filter runs, we were backwashing at least once a day, often 2 or 3 times a day. We also had issues with bacteria for the last bit of the summer.

Frequent backwashing with a sand filter would indicate the problem is either an increased dirt load into the pool, or that a large amount of your sand is completely clogged making your 26" filter work like a much smaller one. If the dirt load in the pool clogs a sand filter often, you'll have even more clogging problems with a DE or cartridge.

The bacteria issue is a chemical issue, not a filter issue unless circulation is reduced to the point that the sanitizer can't do its job. Increased bather load leads to increased sanitizer demand.

 

[deenamccauley]

Jason and John
I should have added that we are considered a public pool as we have a pool at our campground. On average we would have at least 20 swimmers a day with a maximum of 50. So we are pretty busy.
Thus why we are thinking we may need to up our filtering capacity here. I would rather not move to a larger sand filter if I don't have to but it sure does seem like we have to do something.
We have 2 inch pipes (I believe). We did consider putting in a larger pump (2 HP) but were told by one place that our pipes would not work with that size of pump??? Not sure if that's true or not.

I think a large part of our bacterial problems were a high CYA level thus making even the high chlorine levels we maintained rather ineffective.
Interesting....when I took water samples from the controller flow tank I had terrible bacterilogical counts.....but from the actual pool they were better. Any thoughts on that?

During our busiest months we do not go a day without backwashing. 2 or 3 times occasionally. The sand is new, we just replaced it at the begining of May. We will be replacing it again this May only because the person who replaced it broke the manifold so we have to repair that. (This is the same person who raised my CYA levels to 100 and needless to say does not work for me anymore)
With CYA levels that high we ran our chlorine above 10 most of the summer just to try to stay on top of things. We stopped using stablaized chlorine as well and the CYA levels did come down to 70/80 after 4 months.

Any ideas on this are greatly appreciated.

 

[JasonLion]

With that bather load you are no where near having what you should have. Ideally you want to aim for at least 130 to 150 gpm, and then oversize the filter above that. That means something like two 36" sand filters and a much more substantial pump (or two). All that could be hooked up to 2" pipe, but you really wouldn't want to. Pump efficiency is going to fall significantly trying to push that much water through 2" pipes. It can be done, but it isn't usually the best approach.

The central question is probably: how much money do you have to spend to solve this problem? Ideally you are looking at more than doubling your equipment size, probably by using two complete systems each larger than what you have now, and adding additional pipe runs, preferably to different spots in the pool to improve water circulation. That could be a substantial investment.

Short of that, practically anything you do will improve the situation. First priority would be to get a larger filter. Then upgrade the pump. If you can afford it the next step is to double the entire system with independent plumbing to the pool.

That will only take care of some of the problems you listed. Some of your problems are caused by insufficient sanitizer. You need to keep ahead of that kind of bather load, raising the FC level in advance of peak swimming times of day. Lowering the CYA level even further will go a long way to helping with that aspect of things.

 

[duraleigh]

Hi, Deena,

While I agree entirely with Jason, as he suggests, you may be able to improve your situation dramatically without an entirely new supplemantal system.

I would assume you NEVER run your pump on low speed. With that bather load, you need that pump on high. Secondly, what is your pump run time? My guess is your pretty close to 24/7 but post it up, anyway.

Next, if you can't redo the whole system, you must purchase a VERY, VERY large sand filter. Somewhere in the 150gpm range, IMHO. A triton TR-140 may come pretty close to what you need. Purchasing a filter that is tyhe duplicate of what you have and hooking it up in "parallel" to your existing filter might work as well. In short, you clearly need much more filtration than you currently have and you need to run that pump a lot.

Post back what your regimen for daily maintenance was this Summer and you'll get lot's of ideas on how to improve it. As you can see from the above posts, you must increase your filtration to keep your pool crystal clear next summer.

 

[deenamccauley]

Thanks for you input.
At this point putting in new lines is not in the budget. I do have a 2 HP pump available but was told my pipes would not handle it. Is that true? He implied that the pipes would just cave in on themselves.
The other issue is space in my pump room. There really is only room for one filter although it could be larger than what we have now.
Generally speaking we are able to keep the water clear and sparkling but one of my big concerns is with the new laws for pools here we need to be able to have a turnover of 6 hours. I'm quite sure we are not getting that right now. Especially looking at the calculations done here.

I'm new to our Rola Chem automation system as well so I'm sure I'm making some mistakes there. We use 12% liquid chlorine and muratic acid to keep the pH down.
As I said our CYA was very high last season so I kept chloine levels around 10 -15 but I almost always had combined chlorine issues. Which I am assuming contirbuted to our bad bacterilogical counts.???
We completely drained the pool this fall to replace the liner so we will be starting with fresh water in the spring. (Yes, we did put water in it for the winter)
I'm thinking too I may need to make more use or an MPS product to oxidise the organics?
I've never had an issue with algae but I do do a intial treatment and then weekly treatments.
I did figure out to bump up the chlorine prior to heavy use but I was reluctant to bump it up too high when my counts were already so high.
I do run the pump full speed 24/7 the whole summer.
So when you are talking very, very large filter Dave. How large is the filter you meantioned in dimensions? We have limited space. I notice you have a much larger filter than I am running on a 1.5 hp pump. Do you have any pump issues with that size of filter? Is that something I could try first, just putting in a larger filter?
As far as my maintenance regimen:
Aside from testing and adjusting chlorine and pH daily....I do a weekly algae treatment and use an MPS product occasionally. We also use Pool Perfect enzyme on an automatic feeder. I use a sequestering agent at the beging of the season and as needed. I also have used Phosfree but I'm not entirely sure that does much???
Thanks again everyone.

 

[duraleigh]

Deena,

The filter I mentioned is 36" wide and probably 40" tall with a side mounted multi-port. I'm sure there are other brands the same size....I referred to it because I have it and am familiar.....it's been trouble free.

Probably the single most important thing you could do to improve your situation is more filtration. You do not have nearly enough. Your pump will work less and your pool will stay cleaner. As Jason and I implied but probably didn't make clear, that may be the ONLY thing you need to do mechanically to your system.

You didn't ask for this advice but I would suggest you are using W-a-a-a-y too many chemicals that are simply not necessary. Chlorine will keep your pool free of bacteria and algae.

MPS, Algae Treatment, Poolperfect, Sequestrants, and Phosfree are all unneeded items, IMHO, and you are wasting money and confusing yourself by using them.

Read and Reread "The Stickies" section up in the header on this page.........it'll give you some more insights as to what you really need in your pool.

If I owned your pool, I would purchase a sand filter capable of at least 140gpm and replace your existing filter. Then, balance the water (pH and Alk) Check Calcium level, bring my CYA up to around 40-50ppm and then plan on using nothing but chlorine to keep your pool pristine all summer.

The more I read about your situation, the more I think that is all you need to do. You will probably pay for the filter in the money you save by getting rid of the unnecessary chemicals you are currently using.

 

[JasonLion]

There is a "design flow rate" for the pipe and using a 2 HP pump would probably exceed it, but it is a guideline, not an absolute limit. Many people here run their system well above the design flow rate for the pipe and never have any problems. With PVC you can actually go way above the design flow rate before you will see any problems. The total system efficiency does go down a little at these higher flow rates, more energy is lost to friction in the pipes, but that is often a reasonable price to pay.

I would not upgrade your pump unless you are also upgrading the filter. You are already either near or at the design flow rate for the filter and that is a much more important limit than the pipe limit. A larger filter is actually easier on the pump, so you can pair a large filter with a small pump, but not the other way around (a small filter with a large pump will cause problems).

I agree with duraleigh that simply putting in as large a filter as you can fit will be a significant improvement. A 36" sand filter is only a little larger than 36" on the outside, plus you need some clearance for the intake and output pipe connections. You may also need to upgrade the pump to insure a 6 hour turn over, but most of the improvement will come from the larger filter.

I strongly suspect that if you keep CYA around 30-50 and FC around 6-7 that you won't have any significant problems with CC.

 

[DLSDO]

Okay. I probably should stay on the sidelines here and let the pros do their job....but I had a thought.

You described a problem with cloudiness. I would just be curious to see all of your testing numbers....CC/TC/TA/pH/CYA...in particular your CH. I assume your pool is concrete. Wouldn't a high CH also cause cloudiness? I am sure the primary issue is bather load and sanitizer levels/ filtration but a full set of testing #'s might help.

Just a thought.....

 

[deenamccauley]

Okay. I probably should stay on the sidelines here and let the pros do their job....but I had a thought.

You described a problem with cloudiness. I would just be curious to see all of your testing numbers....CC/TC/TA/pH/CYA...in particular your CH. I assume your pool is concrete. Wouldn't a high CH also cause cloudiness? I am sure the primary issue is bather load and sanitizer levels/ filtration but a full set of testing #'s might help.

Just a thought.....

Our pool is concrete with a vinyl liner.
We had only one time of extreme cloudiness, in which I actually closed the pool for 3 days. It was very hot, very sunny and we had a huge bather load for 2 days prior to that. (50 people in the pool at almost any given time, that's our max capacity)
CH 350
PH 7.3
FC 8.17
TC 9.2
ALK 99
TDS 1500
CYA 90
All this was back in July, we are closed now for the winter and we actually drained and replaced the liner this fall so at least we won't be dleaing with the high CYA next season.

 

[DLSDO]

Thanks for posting the test #'s. Your right. Since you drained and refilled you get to start anew.

So whats the plan? Upgrade the filter? I bet that a filter upgrade and keeping the FC adequate for your CYA will be satisfactory.

 

[duraleigh]

dlsdo (Dave),

Okay. I probably should stay on the sidelines here and let the pros do their job.

Absoutely not. The only way I learned about any of this stuff was to become engaged on the forum and ask questions and probe for answers.

As you can tell, there's every level of expertise on the forum. The path to understanding your pool better and having crystal clear water is to stay very active on the forum and participate at every opportunity.

 

[deenamccauley]

Thanks for posting the test #'s. Your right. Since you drained and refilled you get to start anew.

So whats the plan? Upgrade the filter? I bet that a filter upgrade and keeping the FC adequate for your CYA will be satisfactory.

Yes, that is the plan. To upgrade the filter and stay on top of the FC.
If that doesn't work then I guess we upgrade the pump. Which we most likely will have to do eventually to get the turnover rate that the health department wants here (of 6 hours).
Just trying to do it a bit at a time so that it doesn't break the bank.

Thanks for everyone's help.

 

[DLSDO]

dlsdo (Dave),

Okay. I probably should stay on the sidelines here and let the pros do their job.

Absoutely not. The only way I learned about any of this stuff was to become engaged on the forum and ask questions and probe for answers.

As you can tell, there's every level of expertise on the forum. The path to understanding your pool better and having crystal clear water is to stay very active on the forum and participate at every opportunity.

Thanks!!