Slightly cloudy water

andy33gmail

Member
Jul 22, 2018
16
Cambridgeshire, England
I’ve noticed the water in my pool is fairly cloudy. There’s a little fungal activity - a single brush down the vinyl each time I use it keeps it from being slimy, nothing visible.

Chemical balance is fine from all I’ve measured. Circulation moving fine, although filter is stubbornly slimey; I have a single inlet jet, I can see by the turbulance it’s hitting the far side. Tried cleaning filter using both 15% bleach and hydrochloric acid on it (not at the same time!!!).

Should I be looking at a (chlorine) shock and then clearing with sodium thiosulphate, or should I be changing filters? Filters are likely to be expensive as I’m in the UK and the part will be from the US

FC 0.75
CC 0
pH 7.4
CYA 0
TA 40-50
CH 300-350
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Andy, you should never see slime or cloudiness in your water. More than likely you have algae in there, and to remove algae we like to use a process called SLAM Process. That also requires a proper test kit. See Test Kits Compared. Many of us like the TF-100, but the Taylor K-2006C will work also. You have no CYA (stabilizer) so any bleach/chlorine you add is disappearing extremely fast from the sun. Probbaly why your FC is so low right now. You should have a minimum CYA of 30, and now that you have algae, you need a much higher FC level to do that SLAM Process I mentioned (FC of 12). You can see that on the FC/CYA Chart. But you need one of those test kits to test FC that high.

Regular bleach (sodium hypochlorite) or liquid pool chlorine (same thing) are the best weapon do defeat algae WHEN tested and maintained properly. So please look over those links and also our ABCs of Pool Water Chemistry page. Let us know what other questions you may have.
 

andy33gmail

Member
Jul 22, 2018
16
Cambridgeshire, England
Chlorine levels are stable, it’s a small indoor pool and controlled with an ORP monitor. I can certainly increase the FC for a shock - although I’m not sure what I’d go to - typically you’d do 10x combined - but there is no combined!

Interesting point about the filter and acid. I’m not sure what a normal life expectancy would be, it’s pretty nasty, but it seemed worthwhile trying to clean it before replacing it.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I didn't realize you had an indoor pool. Good to know. Might want to add that to your signature later. As for the ORP monitor, I'll leave a note below for an expert on our forum to assist. But you really should consider a minimum amount of CYA. Typically we see a CYA of about 20 or so for indoor pools. So to SLAM the FC level would be about 10.
 
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andy33gmail

Member
Jul 22, 2018
16
Cambridgeshire, England
I’ve pointed the jet up a few of days ago to encourage out-gassing and (temporarily) set the pH to 7.2 to help burn some calcium hardness. This seems to be making the difference. I’ll re-check the calcium hardness tonight :)
 

splashpad

Bronze Supporter
Aug 2, 2017
1,990
SE Kansas!
I’ve pointed the jet up a few of days ago to encourage out-gassing and (temporarily) set the pH to 7.2 to help burn some calcium hardness. This seems to be making the difference. I’ll re-check the calcium hardness tonight :)
I'm surprised you don't run a small amount of CYA (20?) for swimmer comfort & equipment protection, it might mess with ORP?
I would be inclined to raise the FC to 2-3 (no CYA present) and see what happens with that.

Here is a list of test kit suppliers known for the UK
These are what we have for the UK ---

How to Buy LaMotte 7002 FAS-DPD Commercial Series Kits (FAS-DPD Commercial 7 Kit):
UK: poolandspacentre.co.uk or sword-scientific.com or pro-swim.co.uk

How to Buy Palintest: [SP 315C (similar to K-2005) AND/+ SP 300 FAS-DPD chlorine test]
UK: Tel: +44 (0) 191 491 0808 ext. 208 Email: gary.mccreadie@palintest.com or camlabworld.com or pool-chem.co.uk

How to Buy Lovibond test kit:
UK: pro-swim.co.uk or lovibondwater.com or leisureteq.co.uk
 

andy33gmail

Member
Jul 22, 2018
16
Cambridgeshire, England
If I understand correctly, TA comes from about 3 key alkalines including calcium? By outgassing, you raise the pH, then you add acid (or in this case the ORP does) to reduce alkalinity.

Fill water is about 350 TA IIRC, so way high
 

andy33gmail

Member
Jul 22, 2018
16
Cambridgeshire, England
Mknaus, it would appear I had misunderstood something - Thanks for drawing that to my attention. Re-tested hardness and it’s still just over 300 - what has changed of course is the TA has come down to 40. I’ll point the jets straight now, and next time do so sooner - aim for a level of 80 I guess to avoid corrosion. It’s a vinyl vessel, but even so, I don’t want to damage the pump.

I had believed TA to be “calcium hardness + others” - which of course is wrong, because calcium hardness is unchanged when you outgas / add acid. The reason I guess why the cloudiness changes would presumably be that both TA and hardness affect the calcium balance - i.e. propensity to scale up - and also because lowering the pH from 7.4 to 7.2 significantly increases the chlorine’s effectiveness.

I’ve replaced the filter - it’d done 2 years and just wouldn’t come completely clean.

I don’t like the idea of CYA because ultimately it means keeping more chlorine in the water - sure it’s less active in terms of being an irritant etc - but still more to swallow and absorb through your skin. The pool is covered 23.5 hours a day anyway and receives almost no natural light. And given its small size and 24h circulation, circulation is good.