Using UV lights for pool sanitation

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D

dollard

0
Aug 5, 2012
53
San Juan Cosala, Jalisco
I asked awhile back about using UV lights to sanitize our communal pool.
It has now been done. Our pool is about 120,000 gallons. The water for it comes from wells that reach down to hot water (about 130° F). The pool has two large sand filters but no heating system. 3 to 4 times a week the pool is lowered to allow room to add hot water from the wells to heat it. The pool is kept at a temperature from 86° to 102° F. Some chlorine is added to the pool. The water is fairly mineralized and the pH is over 8. In the past we have had problems keeping the pool clean.
So the following changes were made to our system to try and improve the water quality;
2 Spectralight UV lights were installed after the filters, 2 chlorine dispensers-Interwater Clorador Model 1W-0680, and 3 new 2 speed Hayward pumps were installed. It has been 2 months now and the pool is often quite green and cloudy but may be sanitary. Chlorine levels in the pool are now from nil to trace.
The water that was drawn down from the pool went to cisterns where is was stored for watering. Any excess ran down the street.
Our water supply for the homes in our subdivision comes from the same hot water wells. It is stored in several cisterns from where it is sent to the 300 some properties at various times. Now some of the water drawn down from the pool is sent to these cisterns that supply the homes in our subdivision.
Does anyone have any thought or suggestions about this arrangement?
 
dollard said:
Does anyone have any thought or suggestions about this arrangement?
Click to expand...

In the USA, your arrangement would be illegal! You cannot send "used" pool water to storage tanks that feed "potable" water to residential homes. That is a recipe for disease transmission and illness.

As for the pool, no amount of UV will fully sanitize the water, you need chlorine in the water to kill pathogens and algae. If the pool is green and cloudy then it is definitely NOT sanitary.

You must follow the SLAM procedure outlined in Pool School to fix the water problems BUT, without one of the recommended test kits, there is no way to perform the SLAM process.

What kind of test kits are you using??
 
UV does not really fully sanitize the water ... but it can help breakdown the byproducts from heavy use.
And it only does that on the water that passes through the UV system.

For the pool to be safe and to keep the algae from growing, you need to have residual sanitizer within the bulk of the water. And for that you need to keep your chlorine levels higher.

- - - Updated - - -

:shock: oh dang!!! I missed that the pool water is used for home water supply ... that is not good at all :shock:
 
Using pool water for plant irrigation is fine, but please do not use pool water for human consumption, animal consumption, or human/animal hygiene purposes.

Used pool water, even with two UV systems, is not potable water.

What test kit are you using to test/drop PH down to 7.8, test/replace CYA lost during draining/adding, and test/add FC at safe levels? Even with the UV systems, you'll need to test/adjust these. If the UV dealer suggested otherwise - they mislead you or didn't understand what you were using them for.

If you need a test kit, you can see if testkits.net will sell/ship a TF-100 test kit to you via email [email protected] or phone (USA) (919) 528-1454; or as a backup, buy a K2006C from Taylor Technology's international sales: HornerXpress Worldwide in Fort Lauderdale, Florida (954-938-5355) or [email protected].

With either the TF-100 or K2006C we can help you avoid the green and cloudy - and unsafe conditions you've been having to put up with.
 
Lo que están tratando de decirte es que el agua del pozo es muy dura y con muchos minerales. La única forma de mantener el agua sanitaria es con cloro! La luz UV no tiene la potencia necesaria para mantener el agua limpia. Pero el mayor problema es que estás diciendo que el agua que drenas de la alberca la usas para consumo humano y eso no es correcto y lo sé por qué soy doctor! Al menos que te refieras a la alberca como cisterna para consumo humano??? Se gustas explicar mejor en español yo te puedo asesorar!
Saludos
Felipe

Moderator comment: Translation
What they are trying to tell you is that the water from the well is very hard and with many minerals. The only way to keep the sanitary water is with chlorine! UV light does not have the power to keep water clean. But the biggest problem is that you are saying that the water you drain from the pool uses it for human consumption and that is not correct and I know why I am a doctor! At least you refer to the pool as cistern for human consumption ??? You like to explain better in Spanish and I can advise you!
regards
Click to expand...
 
Flying Tivo said:
Lo que están tratando de decirte es que el agua del pozo es muy dura y con muchos minerales. La única forma de mantener el agua sanitaria es con cloro! La luz UV no tiene la potencia necesaria para mantener el agua limpia. Pero el mayor problema es que estás diciendo que el agua que drenas de la alberca la usas para consumo humano y eso no es correcto y lo sé por qué soy doctor! Al menos que te refieras a la alberca como cisterna para consumo humano??? Se gustas explicar mejor en español yo te puedo asesorar!
Saludos
Felipe
Click to expand...


For those of us that failed high school Spanish (I actually took 6 years of Latin), I thank Google for their incredible technology -

What they are trying to tell you is that the water from the well is very hard and with many minerals. The only way to keep the sanitary water is with chlorine! UV light does not have the power to keep water clean. But the biggest problem is that you are saying that the water you drain from the pool uses it for human consumption and that is not correct and I know why I am a doctor! At least you refer to the pool as cistern for human consumption ??? You like to explain better in Spanish and I can advise you!
regards
Felipe
Click to expand...
 
For heating, why not pump the hot water through a heat exchanger?

That way, you wouldn't need to drain water and refill with hot water to heat. You could maintain a more consistent water temperature.

You need better sanitation and filtration. What size sand filters do you have?

Perhaps adding DE or cartridge filters would help.

If you're using a tab feeder, the buildup of CYA will be an additional challenge that you're probably better off avoiding.

Your water is not safe or sanitary. You likely have harmful bacteria in the water.

In addition, the cloudy water makes seeing a distressed swimmer under water more difficult.

What are all of your chemistry readings?

What is your total flow rate?

How many bathers per day?
 
Welcome to TFP! Good to have you here :)

Here's another alternative for ordering a test kit. You will save a lot of money by following Trouble Free Pool Care (TFPC), easily enough to pay for the test kit.
Taylor FAS DPD Test Kit Chlorine - SERVICE SIZE K-2006C $139.99

It's great that you have such a nice source of hot water, but yeh, heat exchange is the way to go, as suggested by JamesW. People should not drink pool water, so make sure those cisterns are chlorinated adequately to stop the risks, and then no more pool water put in them.
 
Wow! Thanks for all the helpful responses.
I am in Mexico where it may also be illegal but that is the setup we now have-so how to make it work well?
We use the basic Interwater test kit. I always thought that we need a better one.
I don't know if it would be possible to drop the pH down to 7.8. It is a large pool.
James W I can't answer all your questions without doing some checking.
Heat exchange sounds interesting I will have to do some reading on it.
 
As you can probably tell by my above post I am not the general in charge of running this pool. I am a user of this pool who hopes he can help in some way to make it run better. My personal concern with this pool is that it is too hot for me to swim laps. I feel like I am suffocating when I do more that a few laps. Many other users like it hot for hanging around in.
 

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You could recommend to them that community pools are usually kept around 80/82F for comfort, and the difference in growth rates of contaminants is massively lower at 82F than the growth rates at 100F. You could also refer them to information showing that chlorine effectiveness goes down as pH goes up and pH above 8 is uncomfortable for swimmers.

As far as putting pool water into drinking water, you could find some information on typical swimming pool pathogens, typical swimming pool salinity levels and the like.

Another option would be to suggest they hire an engineer familiar with municipal water treatment. You could also ask some local docs if they've seen more conjunctivitis, earaches, or gastro among people that use the pool.

Good luck and I hope you're successful influencing the powers that be :)
 
You're doing a good thing helping to make things better and safer!

Suggestions to improve your situation immediately:

1. To avoid them draining the pool down, perhaps you can just keep the cisterns filled with well water at all times so there is no room for pool water in them.

2. Suggest starting a garden or football pitch in an open piece of land close to the pool and when they want to drain the pool down for more hot water, flood the garden/pitch instead of pumping into the cisterns.

3. Might it be possible to make a 2nd, much smaller pool that they can just drain and fill whenever they want really hot water? Like a hot tub. This way they leave the big one alone?

If someone is willing to spend money on a suggested test kit and chemicals... there are three you'll need for sure:

Check with local hardware stores/pool stores/pool builders/commercial pools/etc to see who sells "Muriatic Acid" also called "Hydrochloric acid." Read all the instructions and follow them!!! Store safely away from kids and animals. If you've stored your current test kit in a cool dark place and the ph test isn't expired, you can use it to adjust the PH now, or wait until your new test kit arrives. Keeping the PH 7.2-7.8 will not only make the pool nicer for humans, but will help your bleach be more effective.

Find a reliable source for bleach to chlorinate the pool. The fresher the better and the stronger the better. If whoever is paying for this is up for it, a one time investment in a large enough SWG and salt would be another great option. Either way - this pool must be chlorinated correctly to avoid going green and being unsafe. Bleach will have to be added several times a week, perhaps even daily, in some amounts.

Also check to see who sells CYA or order it online. The correct amount will partially protect your bleach from the sun.

We can help you use PoolMath to determine the correct amounts if this is an option.
 
BattleOfYakima said:
You're doing a good thing helping to make things better and safer!

Suggestions to improve your situation immediately:

1. To avoid them draining the pool down, perhaps you can just keep the cisterns filled with well water at all times so there is no room for pool water in them.

2. Suggest starting a garden or football pitch in an open piece of land close to the pool and when they want to drain the pool down for more hot water, flood the garden/pitch instead of pumping into the cisterns.

3. Might it be possible to make a 2nd, much smaller pool that they can just drain and fill whenever they want really hot water? Like a hot tub. This way they leave the big one alone?

If someone is willing to spend money on a suggested test kit and chemicals... there are three you'll need for sure:

Check with local hardware stores/pool stores/pool builders/commercial pools/etc to see who sells "Muriatic Acid" also called "Hydrochloric acid." Read all the instructions and follow them!!! Store safely away from kids and animals. If you've stored your current test kit in a cool dark place and the ph test isn't expired, you can use it to adjust the PH now, or wait until your new test kit arrives. Keeping the PH 7.2-7.8 will not only make the pool nicer for humans, but will help your bleach be more effective.

Find a reliable source for bleach to chlorinate the pool. The fresher the better and the stronger the better. If whoever is paying for this is up for it, a one time investment in a large enough SWG and salt would be another great option. Either way - this pool must be chlorinated correctly to avoid going green and being unsafe. Bleach will have to be added several times a week, perhaps even daily, in some amounts.

Also check to see who sells CYA or order it online. The correct amount will partially protect your bleach from the sun.

We can help you use PoolMath to determine the correct amounts if this is an option.
Click to expand...
1. You can't keep the cisterns full as the water is pumped into in and then shortly thereafter sent to the homes. With our system the pool must be drawn down to make room for hot water from the wells to heat it.
2. We have a park and clay tennis courts where water drawn down from the pool is used but at at certain times of the year (especially the rainy season) there is excess water to water the park and tennis courts. Previously the excess water just ran down the streets. Now some of the excess is being used for household use. The wells produce only so much water to go around.
3. Some form of smaller pool or hot tub is a possibility but it would be expensive.

- - - Updated - - -

Another question about our pool water.

This is the setup in our subdivision. All ~350 homes have septic tanks. The two wells that supply the water for the houses are deep underneath the homes.
So most of the water from these wells is pumped to a large cistern where it is distributed several times a week to the homes. Some of the hot water from these two wells is also sent to our communal swimming pool 3 or 4 times per week to heat the pool. Before the hot water is added to the pool it has to be lowered from 4 to 16 inches (depending on the time of year) to make room for the hot water. Some of this water that is taken from the pool is sent to the cistern that supplies the homes. As mentioned earlier the water coming to the pool from the wells and that coming from the pool to our drinking water cistern is filtered, passed by UV light, and then some chlorine is added.
Now this water in the pool and the water going to the homes from the pool is tested regularly for coliform and fecal coliform. My question is-should other tests be done on this water?
 
I think you need professional advice to answer your questions, or a chat with the regulator, system designers and/or operators, and/or a look at the operating permits and what's allowed and not allowed. I worked at a site where municipal waste water was used for irrigation (similar ick factor, but much more ick). We had to be particularly careful with OH&S aspects for the crew there, and the regulators assured us that even though the water was not approved as potable, it was entirely safe to drink or get in your eyes, ears, or other places, because the level of treatment was designed to ensure that anyone coming into contact with the water would not get sick. That water was used on active pastures as well, so beef cattle and sheep were consuming it directly. So it's possible to treat the water adequately, but it requires thorough expertise, the right physical plant, and great testing! That water went through five (might have been more) treatment stages before being ready for irrigation.

This might be helpful and there are other links mentioned in the thread: Germy Truth

The pool water would also have elevated salt, which would be a concern to residents on low salt diets.
 

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