Will Draining Water Help With Algae?

[ugadawgs311]

Hello. In about 12 days, I’m planning on having some work done on my in-ground pool to repair cracks and the foundation underneath fiberglass steps. To do so, I need to drain the shallow end of the pool so it’s only 3-4 inches deep (it’s normally about 3-3.5 feet deep). The deep end is normally about 8 feet deep.

The pool is currently green and cloudy (see attached photo). This happens every year around this time unfortunately. I’m not sure if it’s the pollen, poor water management, or something else, but the only thing that has seemed to work in the past is dumping about 20 pounds of chlorine or turbo shock in the pool. However, I don’t want to do this before draining the pool, since I’d just waste all the newly added chemicals.

Once I drain the pool and refill with hose water, will the fresh water help with the algae problem? Or will I still need to do a pretty heavy round of shock? I just recently discovered the SLAM process here and am wondering if I should try that after the refill. Thanks for any help!

 

[JJ_Tex]

Only chlorine will kill the algae. I would plan on a SLAM after the refill. You can also add some chlorine to the pool while they are working to keep the algae in check.

The first step is to get a good test kit. Do you have one?

 

[HermanTX]

We don't use the word shock as that has many different connotations. The
SLAM Process is the best thing to do. Fresh water does not get rid of algae - the only thing that does is chlorine - lots of it.
Have you tested your pool water? Do you have one of the recommended test kits? See
Test Kits Compared If not, order it now you have it for the SLAM process, it is the only way you will get through the SLAM properly.
What is the CYA as that will be a driver in how much chlorine you need to add?

Doing a SLAM after you drain and refill is best because it will lower your CYA which in turns reduces the level of chlorine needed to perform the SLAM.
Suggest that prior to draining that you dump a couple of gallons of liquid chlorine in the pool and brush really good the walls and steps, etc. This way when you drain, you will drain some of that algae out that the chlorine killed. It is worth the $15-20 of liquid chlorine to remove some of the algae. You will not get it all but you be in a better starting position when you refill and reduce the amount of algae that your filter will pick up. BTW, since you are draining the pool, go ahead and backwash the sand filter before you drain. That way it is clean and ready for the SLAM.

Prior to staring the SLAM, have a full test of your water as you need to also know your pH level.

 

[ugadawgs311]

Only chlorine will kill the algae. I would plan on a SLAM after the refill. You can also add some chlorine to the pool while they are working to keep the algae in check.

The first step is to get a good test kit. Do you have one?

I do not - just test strips. Do you have any recommendations?

Also, you think I should add some chlorine now? Would that help prior to the step repair? Or just be wasted chemicals since I’ll be draining a good amount of water in about 12 days.

 

[JJ_Tex]

Herman posted the link on test kits and I’m partial to the TF100.

If it were me I would read up on the SLAM, get supplies and test kit before they start working. Then once you have drained, add some liquid chlorine to the half empty pool.
Then once they are done and you are refilled, start your SLAM and finish off the algae.

 

[PoolStored]

1) Order the test kit now.
2) add 5ppm PER DAY in liquid chlorine to the pool, this will keep the algae from growing worse. Do this until we figure out next steps.
3) When you get your test kit, post results and we can help you with the right order of operations based on your water. For example, if your CYA is high, I would delay slam until after drain and refill. If your CYA is reasonable, I'd slam now and clean it up.

YMMV

 

[HermanTX]

Or just be wasted chemicals since I’ll be draining a good amount of water in about 12 days.

We only recommend using Liquid Chlorine (LC). Sometimes powder chlorine can work but it is usually bonded to some other chemical that is not helpful. Also LC works quicker as it mixes well in the pool with pump running.

JJ made a good point - buy your supplies soon - test kit and about 15 gals of liquid chlorine. A gallon of LC at 10% will raise your FC level by 4.4ppm. For your SLAM, you will need to be at least at 12ppm which is assuming the CYA test is at 30. If it is higher, then your FC level will also increase. So, using my example you will need 3 gals of LC just to start the SLAM and then you have to keep adding LC throughout the day. So be prepared and get the LC within the next 7-10 days.

Furthermore, if you can add at least 1 gal a day until you drain then you might increase the amount of algae it will kill and it will be drained away. The goal is to not let it get worst then what it is now. Not sure what LC prices are in your area but expect about $6-10 a gallon. WalMart seems to be a good place to buy but places like Home Depot also carry LC.

 

[Bperry]

The pool is currently green and cloudy (see attached photo). This happens every year around this time unfortunately. I’m not sure if it’s the pollen, poor water management, or something else, y help!

If it turns green like that it means you aren’t maintaining enough chlorine in the water plain and simple. TFP can help you avoid having that happen again.

 

[ugadawgs311]

Thanks for the responses, everyone! This is very helpful!

Looks like my local Home Depot has liquid chlorine for just under $9/gallon. It’s 10% sodium hypochlorite - will that work for my purposes? Sounds like I should plan on having quite a few on hand to get through the whole process.

What about other chemicals? Or is this step mainly just a heavy purge with chlorine to nuke the algae?

 

[HermanTX]

Looks like my local Home Depot has liquid chlorine for just under $9/gallon. It’s 10% sodium hypochlorite - will that work for my purposes? Sounds like I should plan on having quite a few on hand to get through the whole process.

yes this is great

What about other chemicals? Or is this step mainly just a heavy purge with chlorine to nuke the algae?

We only need to ensure your CYA is at an acceptable level before you start to SLAM and we want to reduce your pH to low 7's before a SLAM (have some Muriatic Acid on hand for the pH)
We can address TA and CH after the SLAM.

 

[ugadawgs311]

Ok thanks. I found the Taylor K2006 test kit on Amazon. I think I’ll go with that one.

 

[PoolStored]

Ok thanks. I found the Taylor K2006 test kit on Amazon. I think I’ll go with that one.

Great, but get the K-2006C, the reagents are larger, which will help with SLAM. Better yet, get the TF-Pro with Smart Stir which has the smart stir.

 

[ugadawgs311]

I’ve got a bunch of HTH granular chlorine 1-pound bags lying around. Could I use those at all here, or should I only use liquid chlorine?

 

[PoolStored]

I’ve got a bunch of HTH granular chlorine 1-pound bags lying around. Could I use those at all here, or should I only use liquid chlorine?

Use Liquid Chlorine. The HTH is likely cal-hypo...which add calcium, which isn't really necessary for a vinyl pool. Without knowing your baseline chemical composition (no test kit), I'd avoid until you get the test kit.

 

[ugadawgs311]

Use Liquid Chlorine. The HTH is likely cal-hypo...which add calcium, which isn't really necessary for a vinyl pool. Without knowing your baseline chemical composition (no test kit), I'd avoid until you get the test kit.

Ok thanks. The test kit should arrive this weekend. I’ll try to pick up some LC by then too.

You’re correct: the HTH is 56% cal-hypo. Hopefully I can use it at some point since I already paid for it.

 

[ugadawgs311]

If the liquid chlorine is 10% sodium hypochlorite and 90% other ingredients, shouldn’t I be concerned what the other ingredients are? If there’s a problem with granular shock containing unnecessary fillers or other chemicals, wouldn’t the same principle apply for a 10/90 mixture?

 

[PoolStored]

If the liquid chlorine is 10% sodium hypochlorite and 90% other ingredients, shouldn’t I be concerned what the other ingredients are? If there’s a problem with granular shock containing unnecessary fillers or other chemicals, wouldn’t the same principle apply for a 10/90 mixture?

Nope, no concern. LC is typically 6%, 7%, 7.5%, 10% and 12.5%. It is just a diluted solution. No worries, good to go!!!

 

[Bperry]

If the liquid chlorine is 10% sodium hypochlorite and 90% other ingredients, shouldn’t I be concerned what the other ingredients are? If there’s a problem with granular shock containing unnecessary fillers or other chemicals, wouldn’t the same principle apply for a 10/90 mixture?

The other 90% is water and a little salt. No worries.

 

[JJ_Tex]

To turn the liquid chlorine into a more convenient solid form, the manufacturers have to add either calcium or CYA. Both are necessary for an outdoor pool.

Unfortunately, we see hundreds of posts a year from people solely using the solid forms of chlorine leading to issues requiring SLAMs and/or drain and refills.

Liquid chlorine should be your go to most of the time, and then save the solid forms for vacations and other times when you cannot add chlorine as often.

 

[ugadawgs311]

The other 90% is water and a little salt. No worries.

Gotcha. Sorry for the dumb question here, but is the main benefit of liquid chlorine just that it’s easier to mix in the pool water since it’s already a liquid? In the end, 10% chlorine in a 128 ounce bottle is more chlorine than 54% of a 16 ounce bag, so I guess the liquid does have more of the chemical, thus probably does a better job of sanitizing.