Debating the turnover is a myth belief

[mas985]

Pedantically the wide spread advice all over the internet is that you require 1-2 turnovers is a general easy to understand concept that is not really that far from a practical generalization that could be applied to 80% of pools to provide good filtration support.

I don't believe it is anywhere close to 80%. The key word here is "require". Again, sanitation is required, filtration is not. What is required is enough run time to distribute chlorine throughout the pool. For manual dosing, that is only about 30 minutes for the average pool. For SWG pools with properly sized cells, that might be 2-4 hours. Plus with low speed of a two speed pump or a VS pump running on lower speeds, it will be a fraction of a turnover. In the winter, I average about 0.25 turnover per day and in the summer with solar running, about 0.5 turnover per day.

If you turnover your pool water once, then industry studies have shown 64% of your pool water will have gone through your filter. This will generally remove suspended particles from your water.

64% is a number based upon full mixing of the incoming water with the existing water. But in reality most pool owners point their returns to create surface patterns to help with skimming. This results in much more water returning back to the skimmer directly from the return which will result in a far lower filtration rates.

But again, any particles that remain suspended in water cannot be filtered out a standard pool filter. In order for particles to remain suspended in water, they need to be less than 2 microns. Everything else will sink to the bottom of the pool before it can be filtered out. So you are better off using a floor cleaner than longer run times.

 

[JamesW]

The concept of “Turnover” started with commercial pools, which do have turnover requirements.

To some degree, the concept got transferred to residential pools.

To a large degree, pool builders were just trying to give homeowners a simple rule of thumb to make sure that they got enough filtration.

Most builders originally installed oversized pumps and told homeowners to get at least one turnover.

This was very simple, but costly advice. Since builders didn’t have to pay for the electricity, they didn’t much care that there was a 1.5 hp pump running 12, or more, hours a day.

Builders didn’t really have much incentive to figure out how much filtration was actually needed. So, they erred on the side of caution and just made up a figure.

The guideline of 1 to 2 turnovers per day can be considered to be a “myth”, in my opinion.

Some people like continuous skimming and filtration to keep the surface clean and the water extra polished. With a variable speed pump, this can be done relatively inexpensively by running continuously at low speed.

In any case, every pool is different and each person should do what works best for them based on their specific situation.

 

[JJ_Tex]

I was thinking about this thread last night when we were cleaning up the kitchen from dinner. We had chicken, so we sanitized the sink and dish that contained the raw chicken to kill any nasties left behind. After that we wiped down the counters and swept the floor.

Those are two different actions we used to clean our kitchen. While both are required, the immediate concern was to sanitize the sink since that action greatly reduces the risk of food poisoning. Sweeping up some crumbs off the floor was secondary and important to keep the kitchen clean, but no amount of sweeping would do anything about the potential salmonella in the sink.

The same goes here for pool maintenance. To properly maintain your pool, you need to sanitize your pool and clean the water. Chlorine sanitizes and skimming/cleaning/brushing/filtering cleans debris out of the water. Both are required, but the priority should be sanitizing first to keep your water safe and algae free.

 

[Leebo]

The actual pump run time you need primarily depends on the relative size of your pool, the pump flow rate, the amount of debris that falls into the pool and the use of solar panels (or not). Every pool is different and each pool owner needs to figure it out for themselves. Historically, the rule of thumb has been to run the pump at least 1 turnover per day. However, that has turned out to be a very poor indicator of actual required pump run time.

That’s the exact quote from Pool School, opening paragraph. I’m not sure there’s anybody in this thread who’s saying filtration isn’t needed. Same time, that’s not the “turnover myth.” The term “turnover” was an over generalization that said you MUST run the pump enough to filter all the water once a day. That’s false. Some need more. Some need less.

 

[Jimrahbe]

I think the horse had died..

Jim R.

 

[AUSpool]

I’d like to have a go at that horse too if I may...

A turnover is simply the time it takes for a given body of water to pass through a filter or filtration device, or total volume divided by the flow rate. There’s no myth but at the same time the idea doesn’t apply to the average pool owner. The problem with this simple definition and application to pools is that from the moment the first water returns to the pool it is possible to re-filter water that has already passed through the filter. Pool returns can be adjusted to enhance this possibility and the flow rate through the various filter types change with time. With all the plumbing and constriction at returns its very difficult to calculate or measure actual flow rates.

If the pool water is dirty, run your pump for longer or vacuum more often. If the water is really clean think about reducing the run time a little.

A retired rocket scientist by the name of Escoabal, R.P. proposed formula with purity coefficients to account for the mixing and re-filtering of water that had already passed through a system. The formulary is given as; turnover (T) = a(G/F) where G is the volume in gallons and F is the flow rate in gallons per hour. a is the coefficient where a = 9.2 for 99.99% filtration. There are coefficients for 99.9% and 99%. This applies nicely in the aquarium industry where flow rates are not impeded over time but does little for the pool industry.

It should be noted that the turnover idea is a very good sales tool for pool shops to sell floculents.

 

[Jimrahbe]

Steve,

Turnover itself is not a myth.. What is a myth is when it is used in the context of ... "I have to turnover my pool water x times a day otherwise my pool will turn green.." No one here cares how many times someone wants to turnover their pool water. We just want to make sure no one runs their pump just to meet some fictitious turnover number.

Jim R.

 

[markayash]

Phil, @Jimrahbe and myself are perfect examples for this discussion. We both run 24/7 and achieve the daily turnover. I just roughly calculated mine and it was 40k gallons a day. But the key is that we aren’t doing it for the sake of being told that we need to achieve the turnover. Jim and I prefer the slow and low method of running the SWG, which just happens to filter the water 24/7 also. Filtering doesn’t necessarily help after a given amount of time, but it certainly doesn’t hurt anything either. My family also prefers the look of the running water. So we achieve turnover for reasons that work for us, not because the pool industry thought it was necessary a few decades ago and is still telling that story today.

i do the same thing, have a spa water fall and like the sound

I will throw In with old pumps cost was an issue but with the newer VS style it’s not as bad

It’s a choice, I know I don’t have to but it does keep my water cleaner looking

 

[borjis]

I'm quite pleased that a 2 hr pump runtime in season is all I need daily.

 

[Katodude]

So to further take this to the extremes. Since the skimming/filtering is only for the stuff floating on the top. The total amount you need for a “turnover” is the surface area of the pool and about an inch of depth. There you have your turnover, should take about 20 minutes!