Anyone knows how public swimming pools are maintained? Do they completely change the pool water at the end of day, or weekly? Anything they do to the pool overnight (just circulate like daytime, or do nothing, or change entire pool water)? Is the water cleaner in early morning than evening because of this? Thanks.
most pools lose enough water through splashes, people and evaporation that they're being refilled pretty regularly. now that is probably only a couple hundred or couple thousand fresh gallons being added at a time, but it indeed does help. some places do this automatically; others you have to manually turn on the fill spout near the diving well.
Pools are generally a bit clearer every morning for the sheer fact that they've been sitting for several hours with no (or if outdoor, few) impurities entering, and the filters have had a nice chunk of time to turn the water over.
Just re-confirming what everyone has already said. At the pool I spend most of my time at (Blodgett Pool at Harvard), I think our filters circulate the entire pool every 5 hours +/- based on circulation flow rate. In a large pool such as ours, water is being added very regularly. Not sure how long it takes us to add a full 750,000 gallons of new water, though.
For us, one of the biggest problems with cloudy water is simply air bubbles. Sometimes if there is a leak in the circulation system, air can leak into the pipes, and cause really small air bubbles in the water, which makes it cloudy.
Also everything else... dirt, grime, hair product, lotion, etc., that comes off of everyone. (There is a good reason they ask you to shower first!)
-Rick
The pool I learned at (Grizzly Pool in Missoula, MT) had a foot pool as you exited the locker room onto the pool deck. They rarely filled it though, and I think they may have taken it out altogether when they renovated the pool at some point. I don't think I have ever seen that at any other pool, now that I think of it.
One thing they do in Europe that we don't have in the US is walking through a foot-pool before going on deck. I have to image that simple step (especially after visiting the rest room!) would help keep the water clean.
(Too bad the heavy perfume/cologne people forget about the "take a shower before entering the pool".)
This year, TN has required all pools to be inspected by the health dept., the same as restaurants. They are also required to post their scores for public view. The university, where I work, drains twice yearly I think. They test the water every 1/2 hour. Their pools are always well maintained. Now the public outdoor pool in the town, where I live, is a much different story....
Mermaid, Hoffman, Blackbeard, and Osterber nailed it. The only things I would add are: 1. Where I live, there are a number of fitness facility pools that the department of health requires to have the water at 82 degrees. 2. Early morning (4-5am) swimmers seem to experience the clearest water of the day, since it is easier for pool techs to work when the pool is least used. Getting a proper ph balance is said to be a pain and even far more difficult when there are people in the water. Therefore a lot of techs work at night. However, also note that the ph levels can be too high in the early a.m. and left at those levels with the mindset that swimmers and noodlers will have those levels down to proper levels by e.g. 9am which will be perfect for potential inspection times. 3. Even if every aforementioned preventative measure is taken, you are still at risk for Crypto. While I was living in Vegas last year, the Salt Lake County in Utah had a county-wide outbreak. At large pools with a lot of kids, they now have everyone exit the pool for ten minutes every hour so that they can test for Crypto and so that parents can change swim-diapers and take their children to the bathroom. I do not swim in any of those pools, though at least one of them was a USMS training pool :)
(Side note: You never fully realize how much chemicals are in pool water until you swim in open water. It amazes me every time. I also prefer the pool water that is run through a salt filtration system vs a sand filtration system. The chemicals seems less harsh.)
I think what mikedivl meant to say was Salt Cell System - not salt filtration system.
hofffam - you are correct there are an assortment of Sand, DE, and Cartridge filtration systems.
A Salt Cell System takes salt water (NaCl), passes it over electrically charged plates (in a process called electrolysis) to release the chlorine in the salt. NaCl in and HOCl out. Although chlorine is not used per se, chlorine is still present.
Yes, pools with Salt Cell Systems have water that is much "softer" and "easier" on the skin. Over time, Salt Cell Systems save money too.
The pH is the key to skin irritation -- too high or too low and you will have issues. The pH of your eyes is approx 7.4 - 7.6 (a greater population on the higher side). That is why the swimming pool guidelines have been established as such. For the ease and comfort of your body (& parts).
Regarding the water temp -- the activities taking place in the pool will dictate the temperature more than the local ordinance in most jurisdictions.
I have never heard of a salt based filter. I don't see how that would work. But maybe I'm just not keeping up.
I'm most familiar with sand, DE (diatomaceous earth), and cartridge filters (usually in home pools).
Ah, salt "cell" system. Thank you for correcting me. I used to swim in a pool at 24hr Fitness that had that system. Whenever water would get in my nasal passages or at the back of my throat, it was really quite tolerable. Now that I swim in two other pools that don't have the salt cell system, I notice the water seems more acidic and less tolerable. I know, don't inhale the water :)
As a 34 season HS swim coach - the pools were drained every July for maintenance. When refilled just b4 the start of girls season I would bring in the team to look at the wateriest put in it. To the amazement of all , it is green like a dirty river! This is the water we drink everyday from our faucets! When you filter it for 2 -3 days it becomes crystal clear. Yes it seems foggy & cloudy but, it still is the cleanest water your will swim it.
J. Not sure how long it takes us to add a full 750,000 gallons of new water, though.
-Rick
Modern fire trucks can pump water at 2,000 gallons per minute, so it would take about 375 minutes or 6 hours and 15 minutes to fill a pool with 750,000 gallons of water
