Adding DE to Sand filter and pressure readings

[Krulligo]

So this year I have experimented with adding DE to my sand filter. I did this first time clear out some finer debris after I finished a SLAM, but wanted to maintain this as a routine after each backwash.

After a fresh backwash, my pressure gauge is reading exactly at 12 psi. I usually need to add 2.5-3 cups of DE powder to get my pressure up to 13. However after a couple on and off cycles on my pool pump, the pressure never recovers back to 13, but drops back to 12 (or a bit above). My guess is that after the pump cycles and filter loses pressure, the DE has a chance to resettle a bit causing less pressure next time the pump is turned back on.

So my question is, should I add more DE after this happens? Or just assume that the DE I added is still doing it's job.

 

[mas985]

You should know if the DE is doing it's job with the dead algae because if not, it will pass right through and end up on the pool floor again.

In reality, you should only need the DE right after the SLAM and you are ready to vacuum the dead algae. After the dead algae is gone, I don't see much point in continuing the use of DE.

 

[Krulligo]

You should know if the DE is doing it's job with the dead algae because if not, it will pass right through and end up on the pool floor again.

In reality, you should only need the DE right after the SLAM and you are ready to vacuum the dead algae. After the dead algae is gone, I don't see much point in continuing the use of DE.

I have been done with SLAM and removing the dead algae for a while now. But what about charging the filter with DE afterwards to keep filtering any fine non-algae debris that falls into the pool - from trees, dust/dirt, etc?

 

[mas985]

DE is really only needed for dead algae as it is smaller than what a sand filter can capture. The rest of the stuff that typically falls in a pool is larger and more easily captured by a sand filter so I don't believe it is necessary on a daily basis.

 

[hirenkg]

Would you recommend once a week DE usage on sand filter, if the pool had clarifiers, floc etc... from the past, and you need them to clean it out from the filter?

 

[mas985]

In general, we don't recommend those products as they cause more problems than they solve. They should never be used to solve algae issues. Only chlorine should be used for that.

DE improves the filtering of smaller particles. But it doesn't help clean a filter so I am not clear on your question.

 

[Mdragger88]

I have been done with SLAM and removing the dead algae for a while now. But what about charging the filter with DE afterwards to keep filtering any fine non-algae debris that falls into the pool - from trees, dust/dirt, etc?

The SLAM Process is not over until you meet all 3 end of slam criteria
You are done when:
CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
The water is clear.
(Crystal Clear w/no algae dead or alive)
You’re not done.

 

[Krulligo]

The SLAM Process is not over until you meet all 3 end of slam criteria
You are done when:
CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
The water is clear.
(Crystal Clear w/no algae dead or alive)
You’re not done.

I did slam like a month ago and got rid of the algae and passed the criteria.

I'm just asking about charging sand filter with DE and pressure on a normal regular basis.

 

[Mdragger88]

I did slam like a month ago and got rid of the algae and passed the criteria.

I'm just asking about charging sand filter with DE and pressure on a normal regular basis.

I mis read- the “removing dead algae for a while now” thing & thought you were still doing so.
You can certainly use de after every backwash if you wish. It does make it to where you may need to backwash sooner.
If you have used floc/clarifiers in the past you may want to do a deep clean of your sand - this is something that should be done every couple seasons anyway.

Deep Cleaning a Sand Filter

This post will walk you through the anatomy of a sand filter, and then provide a video at the end for how to deep clean your sand filter. The filter used in the photos and videos is a Hayward S180T top mount sand filter. The images are of a similar filter. Obviously not all filters are...

www.google.com

 

[Krulligo]

I mis read- the “removing dead algae for a while now” thing & thought you were still doing so.
You can certainly use de after every backwash if you wish. It does make it to where you may need to backwash sooner.
If you have used floc/clarifiers in the past you may want to do a deep clean of your sand - this is something that should be done every couple seasons anyway.

Deep Cleaning a Sand Filter

This post will walk you through the anatomy of a sand filter, and then provide a video at the end for how to deep clean your sand filter. The filter used in the photos and videos is a Hayward S180T top mount sand filter. The images are of a similar filter. Obviously not all filters are...

www.google.com

Thanks but I know all this. In my original post I am asking about DE and pressure. I add DE to increase my pressure up by 1 psi, but after I cycle my pump on and off a few times, the pressure returns nearly back to backwash pressure. Do I need to add more DE to my filter to re-increase the pressure?

 

[Mdragger88]

Thanks but I know all this. In my original post I am asking about DE and pressure. I add DE to increase my pressure up by 1 psi, but after I cycle my pump on and off a few times, the pressure returns nearly back to backwash pressure. Do I need to add more DE to my filter to re-increase the pressure?

No - not if you are getting the results you desire.

 

[Krulligo]

My concern is that it's not working as it should if the pressure is not 1ppm above clean anymore even though the DE is still in the sand filter? Does it just get rearranged in the sand filter when the pump cycles causing it to settle differently?

 

[mas985]

Do you see any DE coming out of the returns? Sand filters can get channeling which allows debris to pass right through.

But again, are you convinced that actually need the DE?

Many on the forum are convinced that they see a difference with DE than without and there are others that do not see any difference. Personally, I think the benefits of DE are a little overblown except for sand filters and algae. The reason being visual acuity. The human eye has a resolution limit:.

Visual acuity - Wikipedia

en.wikipedia.org

0.6 arcmin of a 10 micron particle (something that may pass through a sand filter) is about 1/2". So any 10 micron particle cannot be seen more than 1/2" from the eye. To me, it just does not seem plausible that most people can even see particles that small.

However, dead algae is a different situation. It clumps together on the pool floor so it is easily seen.

 

[Mdragger88]

My concern is that it's not working as it should if the pressure is not 1ppm above clean anymore even though the DE is still in the sand filter? Does it just get rearranged in the sand filter when the pump cycles causing it to settle differently?

If its in there its helping.
If you’re not getting the clarity you want even with the de you may have other issues like needing to deep clean your sand.

 

[Krulligo]

I am definitely not getting any DE passing through the filter. I have watched the return jet as I was adding the DE and the pressure did steadily rise by 1 PSI as I was adding it. Also I did not notice any DE dust in the middle of my circular pool where debris usually accumulate.

The reason why I believe in DE now is that when frustratingly dealing with the last bit of dead algae during my SLAM, in which the sand filter alone could not filter out after over a week of filtering it, adding DE cleared that dead algae in about 3-4 hours time. It was totally impressive and blew my mind. Made slightly dull looking water completely sparkling clean to the point that I believe it is even clearer than it was before my slight algae outbreak. And it did this in matter of a few hours, where the sand filter alone, I did not see any more improvement in a weeks worth of filtering. So I am now a total believer in DE and wanted to keep my sand filter charged with it during regular operation. Just a little perplexed about my PSI and wanted to know what to do. But I guess if the DE is still in the filter, it is doing it's job. Water has been sparkling ever since I finished slam.