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Jul 07, 2011
Has My Filter Gone Bad
by: liz

Help!!!! my pool is green.

We had the water tested at 2 different pool stores, they both say the water is fine.

We changed the sand in our filter and the pool is still green.

Is it time for a new filter or could there be a problem that we are missing.

I appreciate any feedback.

Thank you.


By: Robert
Date: July 7, 2011

Thanks for the question Liz

First, I'd like to have your complete chemicals readings:


CYA (cyanuric acid/stabilizer)



Calcium Hardness

Metals (iron and copper)

Total Dissolved Solids

It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

Without these numbers I'm just guessing at what the problem is. What were the exact readings that the pool store had?

There could be several reasons why your pool is green.

A lack of chlorine is the most common. All of the readings are important, but I would especially need the CYA level.

That acutally could be too high which would render the chlorine less effective.

Is the pool a solid algae green or an emerald clear green? You would approach these from different angles.

Also, did you put enough sand in the filter?

If you do put new sand in be sure to put the correct number of pounds in and get the correct size sand for your filter.

The "freeboard" is the measurement from the top of the tank to the sand.

You can call the sand filter manufacturer and get the correct measurements.

As the sand is used it will start to settle a bit. This is due to the water weight and debris that gets trapped in the sand.

You'll need to back wash, then measure the freeboard once again and top off the sand if necessary.

It may take only an inch or two.

Get back to me with your readings as soon as you can so we can get your pool up and running once again.



By: Liz
Date: July 7, 2011

Thank you Robert for your quick response.

We threw out the exact number from Island Rec. but I tested the water with a testing strip and these are the numbers I came up with me.

Hardness 100

total chlorine 5 to 10

free chlorine 10

pH 7.2

total alkalinity is 40.

Hopefully you can help us. Thanks again!

Jul 07, 2011
Comment By Robert
by: Anonymous

Thanks for the readings Liz

I'm hesitant to tell you to shock with Dichlor chlorine. This is a stabilized form of chlorine that will add CYA into the pool.

You'll need to get the CYA level up, then keep the chlorine level above 12ppm to kill the algae.

If you have an elevated CYA level it will only make matters worse.

On the other hand, I don't want you to keep throwing chlorine in the pool without having any CYA in there.

The best thing to do right now is to shock the pool with regular chlorine at night, then retest in the morning and see what the chlorine level is.

Like I said, the chlorine needs to stay above 12ppm and you need to back wash once per day until the algae is killed.

You'll know this because the water will turn to a white/gray color.

Keep the chlorine level elevated all through this process.

You can also use a PolyqQat 60 algaecide to give you a little more added insurance against another alge bloom while this is going on.

Here are some posts to look over:

Green Pool Water. It's Blue But Still Coudy

Pool Still Green After Many Attempts To Clear!

You'll need to manually dose your pool to keep the level above 12ppm. You might go through alot of chlorine but it's the only way to get rid of the algae.

Here are links to the chlorine pages. They have charts you need for your size pool.

Go just a little over the recommended dose for chlorine. It's better to go a little over than not hit the mark. 12 - 15ppm chlorine is fine for a good shock.

Swimming Pool Chlorine

Pool Shock

Pool Chlorine

There's also more posts on the Q&A in the "Algae/Green Pool Water" category.

Hope this helps and let me know how it turns out for you.


Sep 19, 2011
Walter, 190L jacuzzi
by: Anonymous

Hi, I took mine apart, no problem, the same as detaching from the tank. I have sand in the pool too, but my valve seems ruined. I got it used and tried 3 different gaskets and it leaks in 5 places. I'll give you my old valve if you pay shipping... (but just jr, not junior)

Jun 09, 2013
Sand For Pump
by: Anonymous

Just got a sand filter pump. I went to buy sand for the pool pump and asked them for sand for the pool.

I got home and it was a white powder (earth) which in my pool back home. That's what I used and it worked good but not sure if its ok with a HTH AQUA QUARTZ POOL FILTER. I don't want to burn or ruin the pump.

Thanks for the question

If you have a pool sand filter and have AQUA QUARTZ POOL FILTER you should be fine. The bag should say something like Standard #20 High Purity Filter Sand or something similar. If it says DE or Diatomaceous Earth they gave you the wrong kind.

If the bag you have does say filter sand but it seems too powdery you can always take it back and replace it. Who knows? It may have been mixed up somehow. Most pool sand filter systems require #20 silica sand.


Jan 19, 2015
Replaced The Laterals & Added Sand. Swimming Pool Sand Filter Problems & Possible Solution
by: Warren

Thanks for your reply. We did replace the sand (and laterals) but put in 200lbs per the recommendation for the Laser 190L. Do you think that might be too much?

We are watching and waiting to see how long sand continues to enter the pool. I guess it might be worth pulling it apart again to make sure the sand is not too high. I also suspected, as you mentioned in your reply, that some sand might temporarily return to the pool again for a little while after changing it.

I did inspect the o-ring under the multi-port valve and it appeared ok. We were unable to remove the Adapter flange to look at the o-ring there but nothing is leaking, at least on the outside. The adapter flange would not come off and i did not want to take a chance of breaking anything since Jacuzzi parts are becoming hard to find, never mind the delivery time.

But the adapter flange o-ring should not be responsible for sand returning to the pool should it? Doesn't it just seal the flange to the body of the filter? I was considering the spider gasket or any other inside the multi-port valve as the next place to look if the problem continues. I need to do some research to see if that is difficult to replace or not.

We may also possibly remove some sand to see it that would make a difference. If it is the multi-port valve then I want to understand how the various settings work inside the multi-port valve so I can determine how sand might return into the pool while the setting is on "filter". All the flow diagrams I have found are too basic to get into that level of detail.

Would you know of any that might be more helpful? I understand the directions that the water flows on each setting but haven't been able to relate that to the actual physically opening and closing internal ports of the multi-port valve.

I would love to have an old one I could examine closely. Hopefully, best case scenario, this is a temporary situation which will resolve itself, but I always like to know what my next steps are(plan B) if it comes to that.

Thanks for the follow-up Warren

I know if you put too much sand in a sand filter the filtration process will be compromised. The sand filters at the YMCA have these tubes called "Diffusers" that sit on top of the pipes inside the filter.

If you can imagine a softball sitting on top of a PVC pipe. The water comes in through the pipes and out the diffusers, is pushed through the sand, filtered, and returned back to the pool as clean water. If the sand is too high or low from the top of the filter the pool sand cannot do its job.

Think of it as oil in your car; too much or too little is bad. Check to be sure you're using the correct amount and type of sand. As the filtration process continues there will be a settling of the sand. If you remove some sand, understand that as the new level will find itself settling, some sand may go back into the pool. Once again, that's normal. I believe most diagrams concerning multi-port valves for sand filters will be pretty basic.

They'll tell you what the functions are and give you an understanding for each setting. Maybe you could call your local pool supply store to see if they have an old one or a local pool guy.

After you backwash be sure to use the "Rinse" setting for about 15 - 20 seconds to get rid of the sand residue in the lines. You're on the right track with your sand filter. Check the sand level, mulit-port valve, and O-rings.

If the problem persists, you might want to get a qualified pool tech to take a look at the sand filter. Without actually being there and seeing exactly what's going on, it's difficult to pin-point the issue. At minimum you'll know what the problems aren't so the pool tech can do his trouble-shooting quickly.

Thanks again and let me know how this turns out for you. I'm sure many other people who visit my site would like to hear your story.

Good luck


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