Swimming Pools in France

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Re-occurring fine dirt/dust/aglae in Pool?

I wonder if anyone else has had a similar issue with fine light brown particles and insect bits entering the pool straight after cleaning?

This has been driving me crazy since last year when it first started. So after the season I changed the sand and carefully replace the laterals thinking this year all would be good - nothing has changed.

I had a professional out, who said it was just to be expected with the weather and as we are on a hill - but it never happened for the first 8 years and forces me to clean at least once a day!

Straight after vac to filter it slowly starts to build below the jets and after 3 hours its a patch of fine light brown dust about metre square with some black gritty bits. It then starts to settle on the far end of the pool.

A net isn't fine enough and the particles just disperse then re-group.

The water is clear and PH & chlor spot on. The filter pressure is great and not above the level when new sand was entered.

After vac to waste its slower but eventually builds up again! I kept vac to waste but there seems an endless supply?

I've shocked it thinking it might be an Algae of some sort although water is clear?

I've run the pump on all permutations, thinking I had a leak on one of the lines, but I'm not losing water obviously and I assume it would be forcing muck out not sucking in? It even appears on re-cycle which makes me think there might be a multivalue issue? The the gasket and spring appear to be good, the mechanism is 9 years old?

I've read some informed replies here so I hope if you guys are still reading you might be able to help or had a similar experience?

I have some images I will ad a link to asap.

Hope you can help and save me from pool duty 24/7 for the next three months.

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Re: Re-occurring fine dirt/dust/aglae in Pool?

When you changed the laterals were any damaged? If so that could have been the initial cause of the 'dust'. If you then damaged any whilst replacing them it would lead to what you now have?

You don't indicate where you are? If you are in a wind tunnel, as I am here between the Corbiers and the Montagne Noire, then it could well be airborne sand. I only had our robot in a few days back and it needs to go in again because of those winds.


Never forget that you are unique, just like everyone else.
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Re: Re-occurring fine dirt/dust/aglae in Pool?

Thank you for the prompt reply.

I'm near Castilloness, north lot et garonne. I'm pretty sure its not weather related the 10 x 5 pool is walled on three sides and this only appears when pump is running and started last year for the first time.

The old laterals were not damaged but I replaced them anyway. I can't be certain the new ones weren't damaged but I was pretty careful feeding the sand in with water in place.

Its the fact it also appears on re-cycle and when I closed the multivalve at the 3 oclock mark which is supposed to close all ports the water was pouring out the jet exit.

Here is a link to my pool images, as I say the majority very fine and disperses with a net but obviously heaving enough to settle?
These are 24-48 hours after complete clean or vac to waste:




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Re: Re-occurring fine dirt/dust/aglae in Pool?

Its a very fine silt, sand simply doesn't capture particles smaller than around 20 microns.  When you consider the power of the pumps used on swimming pools a lots of fine particles are just pushed through and back into the pool.

The human eye cannot see the difference in clarity of finely filtered water but it does make pool maintenance easier.  Only when we see dirt which settles out on the floor of the pool do we know that it's not all that great filtration

Vacuuming to waste will get rid of some but it's so fine you have to go carefully to avoid disturbing it and putting it back into solution.  Using a clarifying product like Miraclear which puts a jelly like coating on the top of the filter media (temporarily)  can help but if the pump is too big it can break through that as well.

Re cycle (recirculate) does not close off the ports at all it just passes the water into and out of the multiport valve and back into the pool without it passing through the filter.

*Try putting one of your best cotton towels into the skimmer basket (towel NOT washed with fabric conditioner) this will slow down the water through the system,  cotton can filter out tiny particles as well.

*may cause divorce proceedings. Stick out tongue [:P]

Passivpool Energy "A++" rated Swimming Pools, the lowest running costs in the Universe.
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Re: Re-occurring fine dirt/dust/aglae in Pool?

Sorry I missed this reply. I'm now wondering if its a combination of an Algue in the water and particles finding their way from under the tiles and the top of the liner. Even thou I sealed most of this there are a few gaps ( clinging to straws here I know).

The thing is, I vac'd to waste and all looked good until 3 hours in to next morning when it was as bad as ever. Just doesn't seem consistent.

I have been using skimmer nets which do trap a fair amount of fine stuff so I decided to place a set over the jets by removing the directional ball inside and simply screwing the net on by the collar. Okay it looks a little two contraceptives when the pump is on and worse when they are off, but needs must!
Also there is obviously a drop in the pressure and direction to aim stuff towards the skimmers but I thought I would at least see if it will catch something.
After two days it looked like I was on to a winner, what ever was happening was getting dispersed and nothing appeared below the jets.

Then areas appeared in other parts of the pool with nets on both end, a fine something (I wonder if its an algae) and black grit particles are gathering enough to make the pool look dirty again in a matter of hours?

But with the nets on ( not ideal) I now only cleaning every 2-3 days apposed to twice a day - bizarre!

I now plan to sillicon the gap all around between tile and liner clips. Fingers crossed.

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Re: Re-occurring fine dirt/dust/aglae in Pool?

We had some rain yesterday and I was up in our mezzanine looking down onto our floating security cover and you could see the sand that had been washed out of the air on it. All that will eventually finish up in the pool and it could be what you are getting?

Even our car has been changing colour to a sandy mix. I haven't seen  it as bad as it's been this year and we have been here for 12 years!


Never forget that you are unique, just like everyone else.
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Re: Re-occurring fine dirt/dust/aglae in Pool?

Thank you for that. Yes I agree it is an issue at times, but this happens at least every two days throughout the summer since June last year, and was fine the 10 years before that.
The jet nets seem to be less effective so that line I assume is ok. I think has now blown my sealing the gap between liner and tiles theory as there would need to be some sort of dirt/grit making factory or very busy nests!
Here's another pic if you anyone cares to look. It doesn't seem a lot but this is in 4-5 patches the same size every couple of days.


Many Thanks
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Re: Re-occurring fine dirt/dust/aglae in Pool?

It is difficult to tell from the photo, the whatever is now taking on the water colour in the photo so looks like algae, your earlier photos looked like pollen or fine silt.

I am sorry that chemical levels are "OK" means not a lot unless you describe what you are using to measure it, if its dip strips it could be anywhere levels wise they are only a guess.

As I said earlier, a sand filter cannot capture the fine silt, pool pumps are too powerful and just push it through the gaps in the sand which at best are at least 20 microns. You cant filter out live algae either so it just goes around and around until you change something.
Start with a full analysis of the water:
pH level, Chlorine free and total, cyanuric acid level, alkalinity, water hardness.

The fact you say its been great 10 years preceding could mean the water is now nutrient rich so algae can easily grow, you may have high phosphate/nitrate levels but I suggest starting with the easiest and cheapest things like a full water test with proper equipment.

Passivpool Energy "A++" rated Swimming Pools, the lowest running costs in the Universe.
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