Continuing algae

Andy Nash

New member
Jul 29, 2007
4
Aubigne, France
#1
Hi all. My pool (12m x 6m rectangular - built by Desjoyaux France) is new this summer and I'm experiencing continuous problems with algae. The pool system is uniquely DesJoyaux design - the pump circulates the water back to a filtration bag which I am changing & cleaning every 2 days. I've got the PH level down to 7.0 ( I live in a calceous water area of France) and the chlorine level has been kept high. I've shocked the pool with 2kgs twice this summer and I am cleaning the bottom & sides every day with a robot which operates for nearly 4 hours each time. However, the problem continues. Can anyone advise me as to the next steps ?

edit - moved to Algae by Divnkd101
 

Siamese

LifeTime Supporter
Jul 24, 2007
87
Chicago, IL
#2
Andy,

Welcome to the Forum. I'm relatively new here as well, but in the reading I've done in the past few weeks, the suggestions from the smart people on the board, who will chime in later this morning, will likely fall into two steps:

First, provide a full set of testing numbers: It's important to know exactly what the water chemistry is before treatment suggestions can be given. I'm not sure what type of testing kits are sold in France, but it would be helpful to see these measures:

Free Chlorine
Total Chlorine (or Combined chlorine if using an FAS-DPD test)
pH
Total Alkalinity
Cyanuric acid (CYA or stabilizer)

The most important ones will be the CYA level and FC level as the next suggestion will likely be to bring your pool up to shock level and keep the FC level there until it holds for a day. Without knowing the CYA level, the proper shock level can really not be determined.

The only other suggestion I would have right away is to run your pump/filter 24 hours a day 7 days a week for now. I've not heard about the filter bag concept before, I'm not sure hoe effective they are.

Let us know if you have any testing numbers available.
 

The Mermaid Queen

TFP Expert
LifeTime Supporter
Mar 28, 2007
2,522
Northern KY
#3
Post the info that Siamese listed, and we cah better assist you.

Your pH is a bit low, which can mess up your equipment.

What chemicals are you using on a regular basis... powdered dichlor, I guess, since you said you shocked with 2kg. (Many of us will have to fumble around the metric system with you... maybe a Canadian can help here, or other non-USA resident!! :) )

Welcome to TFP!
 

Andy Nash

New member
Jul 29, 2007
4
Aubigne, France
#4
Algae - prevention & Treatment

Hi Siamese
Thanks for the reply-it's really appreciated. My testing kit requires 4 tiny drops of Cl reactive & pH reactive to be added to seperate specific samples of water taken 40cms below the surface at the opposite end of the pool to the filtering system. The readings then range from pH 6.8 - 8.2 ( with the suggested figure for my water as 7.0) and Cl 0.1 - 6.0 ( with my suggested range between 0.6 & 1.0). My actual readings this morning were pH 7.0 & Cl 5.0 which indicates high chlorine content and spot-on pH. The pool has been kept at this level for over a week now, and Ive been filtering at 24 hours per day since May. The filter bag is being changed every 2 days at the most. But I'm still getting algae growth, especially in the filter bag container and I'm beginning to wonder if the pump is not circulating the water quickly enough as this seems to be the only variable I can't work on. I think I'll take your advice and shock treat again to get back to algae free. I'm also thinking of leaving off the summer (night) cover as there appears to be more recurrence of algae when I use this than when I don't. What do you think ?
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
31,327
Sebring, Florida
#5
Hi, Andy,

Your testing for free chlorine is an OTO test. If you can find one available in France, I suggest purchasing an FAS/DPD test for chlorine and a test for CYA. It will measure very high levels (50+) of chlorine and do so accurately.

Based on your info, I suspect two things may be contributing to your nagging algae:

1. A high level of CYA (stabilizer) which significantly reduces the effectiveness of your chlorine. If you can get to a pool store to have that tested, that will be very revealing. Better yet, if you can find a test kit that will test for both high chlorine levels and CYA, you'll be in business.

2. Extended periods of time when you have the cover on. Generally pools seem to do better when they casn "breath". I suggest using the cover the least amount practicable....I think you'll see improvement.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#6
Only one thing to add to what duraleigh said. The OTO test measures TC (total chlorine). TC is the sum of free chlorine (FC) and combined chlorine (CC). FC is what kills algae and keeps your pool sanitary. CC is an intermediate breakdown product that doesn't contribute to keeping the pool clean. Because the OTO test only measures TC you don't really have any way of knowing what your FC level is, which is the one you want to know. That is why it is so important to have a test kit that measures FC and CC separately.
 

The Mermaid Queen

TFP Expert
LifeTime Supporter
Mar 28, 2007
2,522
Northern KY
#7
Maybe things are different in France, but That is a huge pH range... most here would say 7.2-7.8 is ideal.

Also, the chlorine numbers don't make sense to me. Do you have some kind of mineral system on your pool?

You really need to get to a pool store and have your water tested for now, and get yourself a good test kit that has FAS-DPD for chlorine, and CYA, TA, PH, CH.

I just realize I started to reply 90 minutes ago, and forgot to submit this!
 

Andy Nash

New member
Jul 29, 2007
4
Aubigne, France
#8
Many thanks to all of you for your advice. I'll find a better testing kit this week and see how this goes. I'll keep you all posted as to how I get on in the next couple of weeks, using the advice you've given me today. Cheers to all
 

Andy Nash

New member
Jul 29, 2007
4
Aubigne, France
#9
Algae in France

Three weeks after receiving your excellent advice, I can now report that my algae problems have disappeared. I bought a different testing kit (AquaChek) , which included Free Chlorine , pH, Total alkalinity and stabilizer analysis . Using this, I immediately discovered that my pH was way too low. 2kg pH+ later , balance was restored and algae eliminated. What I don't understand is why a major swimming pool manufacturing company such as Desjoyaux can provide an inferior, inaccurate 5 euros testing kit for new customers, when they also stock the accurate 7.50 Euros AquaChek kit. Perhaps I'll contact them and try to find out. I'll let you know the outcome ( if there is one). Thanks again for all your help.
 
Aug 13, 2010
1
#12
Andy, I am considering a Desjoyaux pool and wanted to know what you think about yours. My biggest concern is that they don't use a drain. Of course, according to them, this is "cutting edge" but I confirmed with Desjoyaux reps yesterday that you have to use a vacuum for heavier impurities - like sand.