Help with pool going green

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killynz

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Mar 13, 2016
15
Auckland, New Zealand
I have an in ground fibreglass pool with a Viron EQ swg which also handles automated acid feeding.

Unfortunately my pool has started to go green and I don't know why. My test readings are as follows:

FC 4.0
CC 0.2
CH 170
TA 30
CYA 50
PH 7.0

I realise that I am not quite in line with the chemistry recommended here so is that likely to be the reason that I am getting algae? I have recently turned the SWG down a bit as the FC had gone up to 15 when i left the pool covered for a few days but I thought, clearly incorrectly, that as the FC level was at 4.0 I shouldn't be seeing any algae.

Any pointers would be much appreciated as I am keen to squeeze as much swimming in before the season ends here in New Zealand :)

Killy
 
Killy,

Welcome to TFP... a great place to find the answers to all of your upside-down pool questions... :shark:

How are you getting your test results? I ask, because if your test data is accurate, I too would have thought that an FC of 4 ppm would be ok...

If your CYA is really at 50 (Low for a saltwater pool) then I suspect that your FC dropped well below 4 ppm...

Maybe it is not algae... Have you run an Overnight Chlorine Loss Test.. OCLT..? If not, do that first and see what the results are... Here is how... Overnight Chlorine Loss Test

Thanks,

Jim R.
 
Hi Jim,

thanks for the quick reply. I should have mentioned that I am using a Taylor K-2006C test kit that I imported into NZ (with a bit of difficulty!) from Amazon. As far as I can tell from the test, the CYA is 50-55 but I erred on the side of caution and took the lower number. I do have a big bucket of CYA so do you think that raising the level to 70-80 would be a good idea anyway?

I have had the pool uncovered for the last week or so and we have had warm weather during the day so could it be possible that the chlorine levels are dropping so low in the daytime that this problem has developed and the SWG can't keep up with it?

I haven't done the OCLT but I will do that tonight and report back tomorrow.
 
killynz said:
Hi Jim,

thanks for the quick reply. I should have mentioned that I am using a Taylor K-2006C test kit that I imported into NZ (with a bit of difficulty!) from Amazon. As far as I can tell from the test, the CYA is 50-55 but I erred on the side of caution and took the lower number. I do have a big bucket of CYA so do you think that raising the level to 70-80 would be a good idea anyway?

I have had the pool uncovered for the last week or so and we have had warm weather during the day so could it be possible that the chlorine levels are dropping so low in the daytime that this problem has developed and the SWG can't keep up with it?

I haven't done the OCLT but I will do that tonight and report back tomorrow.
Click to expand...


Killy,

Raising the CYA to 70 or 80 will not help prevent algae, but it will keep the sun from burning off your FC so quickly... Your pool will work fine with a CYA of 50, it will just use more chlorine.

If you do fail the OCLT, then you will have to do a SLAM... so here are the instructions for that... SLAM Process

Good Luck,

Jim R.
 
Welcome to TFP! Good to have you here :)

You can switch to the 10 ml sample size for FC and CC. That will conserve the test supplies and is plenty accurate (1 drop = 0.5 ppm)

The OCLT test (Overnight Chlorine Loss Test) is a really handy test, and be sure to follow it to the letter. (test after mixing, after sunset, then again after water is stirred by the pump, and before sunrise; SWG must be off over night)
 
OK, I did the morning test and my FC level is 4.8 so it has fallen by 1.6 since last night which presumably indicates algae or something else i don't want so SLAM is the next step, correct?

The water hasn't been green for very long at all, probably less than 48 hours. I have included a couple of pictures but to be honest it is quite difficult to make out because the pool is a blue/black fibreglass and it doesn't show up that well in photographs. In the first picture, you can see on the edge of the step a green line which is the most visible part. The one with the red area circled looks slightly greener although it really doesn't come out that well in the photo. Effectively what it looks like in real life is a greenish film over some of the flat surfaces in the pool but not absolutely everywhere. If i brush it with my pool brush then it kicks up the green film and it is obvious against the white brush bristles.

Hopefully this is helpful and sorry about the bad pictures, photography is clearly not my strong suit!

20180311_083834.jpgInked20180311_083826_LI.jpg
 
I know this will sound silly but are you running your pump long enough? Maybe the timer was changed or one of the metal trip things loosed a bit and moved shortening the run time? (If you have in Intermatic type timer). Probably not what happened but certainly worth checking. Personally I'd increase the pump run time until you clear up the algae issue. Of course when the pump is off you're not filtering.
 

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I would go ahead and SLAM it. Double check that pH is still 7.0/7.2 and take it to 20 ppm FC right away. Your pictures don't look bad at all, though I have to admit I'm not 100% sure what I'm looking at. I think a SLAM will be brief and you can keep swimming. The OCLT greater than 1.0 is all the reason you need to SLAM.

In my accent, does your name sound like keely? Just need it straight in my head, ta. Cheers :)
 
Nectarologist said:
I know this will sound silly but are you running your pump long enough? Maybe the timer was changed or one of the metal trip things loosed a bit and moved shortening the run time? (If you have in Intermatic type timer). Probably not what happened but certainly worth checking. Personally I'd increase the pump run time until you clear up the algae issue. Of course when the pump is off you're not filtering.
Click to expand...

My pump runs for about 12 hours a day (8-8 with a half hour lunchbreak :p) and its all digital so no issues with the timer. It is a variable speed one too and I generally run it on the lowest speed as it is fast enough to turn over the whole pool in about 8 hours which I was advised is more than enough. The fastest speed would circulate the whole pool 3 times in 12 hours but it is noisy and uses 7 times as much power(!) so I generally avoid doing that.

One thing that I have just thought about though is that my pool installer has both of the return jets facing straight ahead, should I have these pointed downwards to stir up the water a bit more when filtering out the algae?
 
needsajet said:
In my accent, does your name sound like keely? Just need it straight in my head, ta. Cheers :)
Click to expand...


I don't think it would be like the girls name Keely - at least I hope not because I'm a guy :). It's pronounced like the word kill with a 'y' on the end - its an abbreviation of my last name that originates from Ireland.

I have gone ahead and added some liquid chlorine into the pool. I only added 4 litres as that was all I had lying around but I will pick up some more tomorrow when the pool shop reopens. Hopefully it should be looking a bit less green in the morning though.

I notice in your signature that you are using the K-2006C, can you order that in Oz or do you have to mail order it from the states? I got one from Amazon but it was a bit of a prick to actually get it here as Amazon wouldn't ship it and I had to use NZ Posts reshipper address and they initially refused to ship it because it had chemicals in it! They relented when I sent them the safety docs from the Taylor website but it was a bit of a rigmarole and it would be useful if I could order it from somewhere a bit more local.
 
Thanks for explaining, Killy, now I got it :)

Have a read through the SLAM article and be prepared to follow the written instructions to the letter (I'll just add that I'm a strong believer in starting at pH 7.0 or 7.2). There's a video as well that give you a rough visual idea of how it's done. It takes a few days at least and sometimes a week or more, but once done, the pool will use less chlorine and be considerably easier to look after. SLAM Process

The best deal down here is the ClearChoiceLabs kit Total Pool Water Testing Kit, Salt Water Clear Choice Labs and they also do refills (all Taylor stuff). You can refill the Taylor bottles for most tests. The FAS reagent has to stay in the CCL bottle and it's just a hair too wide for the same spot in the Taylor box but it fits in the middle. CCL has a compatibility chart on their website.

I got my Taylor kit shipped by poolvacparts.com (Arizona). Pool & Spa Warehouse in Sydney has the Taylor K-2006C at around AU$340.
 
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