Any concerns about SLAM'ing my pool?

[mgianzero]

I've been taking care of my pool for years and algae is always sneaking up on me, regardless of how diligent I am about chemistry. When my pool gets overwhelmed with algae, I simply SLAM it and start over. I find that when I SLAM, the pool cleans up in days. So far I've had to SLAM it twice this summer.

I just had a "pool expert" in the area evaluate my pool and he told me that you should only "shock" your pool maybe twice a year otherwise it can cause more problems. Is there any truth to this? What problems can it cause?


Marc G.

 

[mknauss]

Using sodium hypochlorite - aka bleach - will not do anything harmful. I am more concerned on why you lose control of the water chemistry when you have a SWCG. You do not show what location you are in, so you might have to be more diligent on CYA to ensure the chlorine created by the SWCG is being protected.

 

[mgianzero]

My Pool description:
I have a pebble-coated pool (about 25,000 gallons) with a SWG, a secondary tub with three fountains, 2 shear descents inside, all connected by a spillway. I also have a raised hot tub connected by another spillway. I run my main variable-flow pump at 50 GPM for around 12 hours daily and I run my "water features" secondary pump AND hot tub booster pump (runs additional 6 jets in tub) each for 15 minutes daily to keep chemicals circulating everywhere.

My last chemistry test showed this:
Chlor = 4.5 (CC is always zero), pH = 7.4, , TA = 60, CYA = 50.

I check my Chlorine, pH at least every week and do my best to keep Chlor 4-7 and pH 7.4-7.8. My last CYA (about a month ago) was around 60 and my TA never seems to change much - usually always around 60. I thought these results were fine (maybe some low but acceptable values) according to TFP advice. I also measured my phosphate levels for the heck of it - they were also immeasurable (< 200 PPB).

I try to brush the pool, hot tub and fountain area about once a week (or pressure wash - easier since I have lots of rounded corners in the pool). Seems that whatever I do, I have to SLAM the pool 2-4 times a year to keep algae down. Takes about 4-6 weeks after SLAM to start showing more algae.

I had a pool service man come by and he confirmed that I had an algae problem (grows on ALL the walls, and lays on the bottom but easily brushable). He also said that my CYA was too low. (he likes it 70-80's). He also said I needed to get my TA to at least 80 (but prefers around 100). He thought these reasons were why my algae always comes back so easily.

Really? Could it be TA around 60 and CYA around 50 be the source of the problem? I know they are a little low, but really?

 

[mknauss]

Location?

 

[woodyp]

TA has nothing to do with your algae issue. Your level of FC and the ability to maintain that in our acceptable levels of minimum and maximum does. A CYA of 50 is tool low for your SWCG to maintain a residual of minimal FC. 70- 80

 

[proavia]

What test kit are you using?

With a SWG and recurring algae issue, dauly testing is necessary until you get to know your pool and what it needs. Once that occurs and using a SWG, testing every other day or at leat 3 times a week is good.

Are you familiar with the PoolMath app?
Use PoolMath and share the logs here.
Also be sure youare tracking CSI in PoolMath

Post a full set of current test results

FC
CC
pH
TA
CH
CYA
Salt
Water temperature

Edit your account details to add your location

https://www.troublefreepool.com/account/account-details

Edit your signature to add your test kit(s)

https://www.troublefreepool.com/account/signature

 

[mgianzero]

Yes, I do have PoolMath app. I can start using it again.

But what should be my next step? I just bought some more liquid chlorine. Should I shock now at the lower CYA level (so I don't need as much) and then raise my CYA levels to 70-80 once my overnight FC test is < 1 ppm? Or should I just get my CYA to target range now?

Is TA of 60 okay? It says 60-80 in ideal levels notes from TFP. I guess the best way (and possibly cheapest) to raise it is with baking soda. I find that my TA rarely ever changes much throughout the year - always around 60. So I've stopped checking it as frequently as my other tests like FC, pH and CYA.

My test kit is the TFP-100 test kit sold here. I tend to buy a new kit every 1-2 years to keep the chemicals fresh.

 

[duraleigh]

It seems you have all the tools to SLAM the pool but you do not have a clear understanding of the process. Importantly it IS a process and not a one-time dose. It is also EXTREMELY important to understand algae reoccurs because of inadequate chlorine.......nothing else.

Please read "Pool Care Basics" up in Pool School. Follow the SLAM article precisely and then maintain your FC based on a CYA of 50. Keep that SLAM value chlorine in your pool until you complete the SLAM process. I don't think you have been completing the SLAM

 

[mgianzero]

It seems you have all the tools to SLAM the pool but you do not have a clear understanding of the process. Importantly it IS a process and not a one-time dose. It is also EXTREMELY important to understand algae reoccurs because of inadequate chlorine.......nothing else.

Please read "Pool Care Basics" up in Pool School. Follow the SLAM article precisely and then maintain your FC based on a CYA of 50. Keep that SLAM value chlorine in your pool until you complete the SLAM process. I don't think you have been completing the SLAM

As much as I appreciate all the help, why do you say I do not understand the process? I never said it was a one-time dose. My understanding is that "shocking" is adding chlorine to raise levels higher than normal to a designated "shock" value to kill algae, but that SLAM'ing is a procedure (takes several days to weeks) which includes shocking, but in combination with the overnight FC test. (ONCL) test.

These were the steps I took for one of my SLAM'ing procedures ...

Twice, over the summer, I decided to slam the pool because algae got out of control. First, I made sure my pH was low normal as I know it's not accurate to test while SLAM'ing (had around 7.4). After hitting the pool with liquid chlorine at shock level (can't remember the exact number at the time, but I believe it was around 16,) I confirmed that the process was complete (I think it took around 5 days) as I eventually had an overnight FC drop around 1 ppm. During that week, the pool was in service mode - circulating the water 24 hours / day. I would brush once a day, even thought there wasn't much to see after day two.

I ended up keeping FC high over over a week afterwards even, to be certain there was no more residual algae still living in my pool. I then took apart my filter and washed all the cartridges thoroughly (there's not really any mention of this in the SLAM instructions, but I assumed that was the time to remove all the "dead" algae from the filter). I then got the CYA up to around 60 after SLAM'ing and never let the FC go below 4. The TA was around 60 (it's always been around that - never seems to change).

Here were a few questionable things I did as it was not clear on TFP about this. (Perhaps someone here can address my comments below)
1) I know my TA was low normal (around 50-60) before starting SLAM, but I figured it's best to leave it at this lower level until SLAM is complete - otherwise it would require more chlorine to SLAM, correct?
2) During the SLAM the FC would trend downwards (as a positive overnight free chlorine loss > 1ppm) but I kept it at the designated SLAM level or above for the 5 day process by adding more chlorine. I checked these levels maybe twice a day at the time.
3) After my SLAM, I took apart my filter and washed all the cartridges thoroughly (there's not really any mention of this in the SLAM instructions, but I assumed that was the time to remove all the "dead" algae from the filter). TFP just says "Backwash or clean the filter as needed" which I think is pretty vague as to what to do so I waited until I completed the SLAM. Is this wrong? I didn't bother washing filter before SLAM since it would accumulate even more algae during the process.
4) I pretty much ignored the pH during the SLAM since I was told it's inaccurate during high FC levels. But once it trended below 10, I started to remeasure it and add acid accordingly.
5) I turned my SWG cell back on after ONCL test was normal, but with still high FC in the pool (around 10) just to be certain there was no residual algae. I figured there's no harm in running it during high levels of FC in pool. It would just keep it elevated for a longer time period.

Again, my last chemistry test showed this:
Chlor = 4.5 (CC is always zero), pH = 7.4, , TA = 60, CYA = 50. Temp is 75 degrees F.

So back to my original question ... there's algae again in the pool. This time was probably because I went away for a bit and didn't tend to the pool. We haven't been using it for past 3 weeks anyways so I mostly ignored it. Brushed it maybe a week and a half ago last. In last post was my last chemistry test. Should I SLAM now, or do something else like raise the CYA and / or the TA first? Like I said, I had a pool serviceman come by and said he could fix it easily but recommended I did not "shock" (or SLAM) the pool as this is not good to do very often. So I don't know what his plan would be. I told him I don't like using algicides as they seem to be frowned upon at TFP. But maybe that was part of his plan.

What's the consensus here as to my next step?

Thanks for listening!

 

[JJ_Tex]

Your next steps:
1. You have algae, start a SLAM. It sounds like you know the process, but read up again on the slam a few times and make sure you are following it exactly, especially the 3 exit criteria.
2. After the SLAM, keep your FC higher than you have been. 4.5 is not working for you so you need to go higher.
3. Part of your problem may be you are keeping your CYA lower than recommended for a SWCG. Get it into the target range of 70-90. Note, you may have to re-evaluate your FC level and bump it up a bit once you do this too.
4. Mess with your other chemical levels, if you want, but they are not a factor in your algae issue.

For reference, I keep my CYA in range and my FC between 5 and 10. In 3 years, I have never had algae, strong chlorine smells, irritated eyes, high CC, equipment problems, bleaching of swimsuits, etc. My pool is ready to handle kid germs, bird poop, and whatever else gets thrown at it. On several occasions, I have been complimented on my pool and how they are amazed how they do not have the issues they get when swimming in a "chlorine pool". I just smile and say thank you, and do not try to explain that they are currently swimming in a much higher chlorine level than probably any they have ever swam in.

 

[Newdude]

What's the consensus here as to my next step

SLAM it to clear the algae. Raise your FC target to keep it away. You want to be sure that the FC never dips below the 5. If the pool swings 3ppm a day in the peak season, then that makes your new target an 8 instead of a 5.

Also, raise the CYA to 70 to help keep more of your FC protected from UV.

*Edid cuz JJ beat me. What he said.

 

[Mdragger88]

What they said
visible algae = slam time
A few notes:
*ta has nothing to do with algae or the efficacy of the SLAM Process your ta is great especially with all the water features you have that contribute to ph rise.
*Clean your filter when pressure rises 25% over clean pressure- whether you are slamming or not
* during normal (non slam) times, if your cya is too low your fc may be falling below minimum in certain areas of your pool at times (especially on high uv days). It can be hard to catch this phenomenon if you only test weekly or only test after the swg has run all night & caught back up etc.
the solution is to raise cya to protect more of the chlorine your swg produces (after passing ALL 3 end of slam criteria) & raise fc accordingly FC/CYA Levels
Keeping fc a little higher than target harms nothing & is good insurance. Keeping fc right on the edge of minimum is flirting with algae & other nasties.
* you mention scrubbing the filter after slam but what about all the other nooks & crannies during slam?
Recurrent algae can often mean it’s hiding out somewhere just waiting for fc to get borderline low. Check/scrub light niches, drain covers, skimmer throats, weir doors & their foam, ladder rails, rock features etc. Run water features at least a couple hours daily during slam, also be sure to check & flush out any “abandoned” lines , overflow drains etc.
Slam level for cya of 50 is 20ppm.
Maintaining fc anywhere between minimum & slam level for your cya with liquid chlorine will not harm your pool, equipment or swimmers.
Only you can decide who’s advice to take, TFP or the pool service, the two methodologies will likely clash more than agree.
Algae is like the canary in the coal mine- it’s presence indicates that fc has fallen below minimum acceptable levels at some point. Using algaecides, even if effective, add things you don’t want in your pool that can cause other issues & are only solving the symptom(algae) not the real problem (low fc).
Clear water doesn’t always mean safe water.
I personally want safe water - not just algae free.

 

[mgianzero]

Thanks everyone for chiming in. My plan then is to lower pH to 7.2, recheck my CYA and FC before before determining my target levels for the SLAM process.

One of the problems I find with SLAM'ing is that it can be difficult for me to do an overnight FC loss test every night since I have to work early in the morning most days (before sunrise). But I can test FC in afternoons when I return and I might have someone check FC levels during the day. I figure as long as it stays over the SLAM target, I should be fine. I sometimes go a bit over the target to give myself more time before adding more chlorine.

Regarding spots where FC and CYA may drop, I do have what I call a "bubbler tub" which is about 6 inches deep and has three fountains inside, with a spillway and two shear descents on the walls behind it. I run this about 10 minutes every day to mix with pool water. This may be a source of low CYA / FC levels. How often do people suggest I run this tub and for how long after the SLAM procedure? It's on it's own pump, which is also connected to 5 water sconces on two raised back walls of the pool.

I also have an auto-pool filler valve with float connected directly to the pool as a separate compartment area. Probably best to scrub this little fill tank too.

Then I have a Dolphin robot which I run in the pool weekly. I often times keep it in the pool when we're not using the pool out of convenience. Personally, I like that it circulates the water on the bottom and walls to better mix chemicals everywhere. Is there any harm to keeping it in pool and even running it during SLAM?

I use a pressure washer underwater most of the time in leu of brushing because I find it agitates the water better and more easily to reach all areas compared to brushing. I have two raised walls which can be difficult to scrub with a standard pole and brush, but my extending wand on my pressure washer gets everywhere.

 

[mknauss]

Regarding spots where FC and CYA may drop, I do have what I call a "bubbler tub" which is about 6 inches deep and has three fountains inside, with a spillway and two shear descents on the walls behind it. I run this about 10 minutes every day to mix with pool water. This may be a source of low CYA / FC levels.

That is your issue very likely. Does algae show up in this 'tub'? Being very shallow creates a ripe climate for algae. Likely need to run it much more often to prevent algae buildup, especially when the water temperature is above 60F.

There is no need to do an OCLT every night. Only once the pool water is crystal clear and there is NO dead algae debris left in the pool.

 

[Newdude]

What time do you go to work ? There is 'early', which still allows the pool to be UV free (dark) for 8-10 hours, and 'stupid early' which means you woke up today and it was really still yesterday.

Anywho, think of the longest sunshine day of the year in June, the sun is down for about 8 hours. Even if you go to work stupid early at 2AM, you can squeeze 8 hours of darkness in for the OCLT, 6P-8A. If it's lost 0 FC in that long, you're good.

*after the water is clear.

 

[mgianzero]

Got it. So assuming my pool is 25,000 gallons (it's a very odd shaped pool and very difficult to estimate) and shock level is 20 (starting at FC of 4.5) - that would mean I'd need about 3.9 gallons of liquid chlorine (pool store grade at 10%) according to my calculations to REACH a FC level of 20.

Sorry, but I have just a few more questions:
1) Is it safe to say that if my FC dips below 20 (since I sometimes work long days and cannot attend during the day) that it's okay - I just add more liquid chlorine at next test to raise above 20?

My understanding is that I'm primarily just watching for 3 exit criteria. For some reason I have never shown ANY CC level in my pool testing in 20 years (just never positive) and the pool always clears up pretty much completely in 3-4 days. So I think the overnight test is really the one criteria I need to focus on.

2) What about running my robot during the SLAM? Is that okay? I feel it really stirs up the water on the bottom and the walls.

3). When is it best to turn my SWG back on? Once I pass the ONCL test and stop shocking? I know if left my SWG on during a SLAM then your ONCL test won't be accurate, but I was wondering if it's harmful if left on during a SLAM. During one SLAM I forgot to turn it off the first day or two, but then turned it off for the remainder of the process.

 

[mknauss]

1) Is it safe to say that if my FC dips below 20 (since I sometimes work long days and cannot attend during the day) that it's okay - I just add more liquid chlorine at next test to raise above 20?

Correct. No need to go above SLAM level FC. Simply add liquid chlorine to get back to SLAM level FC as often as possible, no less than twice a day.

So I think the overnight test is really the one criteria I need to focus on.

First is crystal clear water and no dead algae debris.

2) What about running my robot during the SLAM? Is that okay? I feel it really stirs up the water on the bottom and the walls.

You can use it. Might want to remove it and wash it down between runs.

3). When is it best to turn my SWG back on?

We generally say to turn the SWCG off during a SLAM, especially the start. But up to you. Nothing harmful, on or off.

 

[mgianzero]

Thanks so much! - That helps to clarify some things.

Off we go to the pool store for some liquid chlorine!

 

[mgianzero]

So I SLAM'ed my pool today. Actually got in it an pressure-wash brushed entire pool and cleaned and ran my robot as well. Initial shock level was 20.5 which correlated nicely with TFP SLAM chart. 4 hours later and pool is looking so much better - no obvious green algae on any surfaces, but water is somewhat cloudy, which I expected.

Just a quick story ... went to pool store to purchase liquid chlorine and granulated CYA. I met up with a pool serviceman there - he gave me his card. I asked if he ever uses algicides or phosphate removers in his customer's pool. Surprisingly, he said "No. Not if you keep good chemistry, it really isn't needed." I was impressed with his answer. Then he asked why I bought all the CYA (bought 4 lbs of granulated CYA) and I answered that once I slam my pool that I will raise it from 50 to 70+. He said for me NOT to because it could cause a "chlorine lock-out" - what does that mean? Sounds like more gibberish from these so-called "pool experts". Darn, I almost thought he was a on the right track!

 

[mknauss]

Chlorine 'lock' is a pool store term. It is when your CYA is very high (100++) such that your FC is not effective at levels below 10 ppm. 70 ppm CYA does not give you chlorine 'lock'.

Stay with the process.