Added de question about pressure rise

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kyle11

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May 17, 2012
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Just added 2 cups of de in increments 15-20 minutes apart and got my pressure up 1psi. Starting adding at 5:15 central so a little over 2 hours ago. Pressure is now up 3 psi to 8. Running pump at 1800 rpm around 55%. I added de to get rid of fine dirt the sand filter is not catching. I have brushed the pool to stir up the dirt. When should I expect to backwash? I go to work at 8 in the morning. What psi should I be looking for tonight and in the morning to feel confident I can leave the pump running during the day. Or should I run it all night and turn it off for tomorrow? Maybe do a super chlorinate tonight to up my chlorine so I don't run low tomorrow? I know I am suppose to backwash around 15psi at 1800rpm since my staring psi is 5 but how far over that can it go? Sorry for all the questions just wanting to get the best coarse of action.


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We usually say to backwash the filter when the pressure goes up 20-25% of the clean pressure ... although that is usually based on single speed or high speed. Waiting for the pressure to go up 10psi at a low speed seems like waiting WAY too long. And doing it at 20% from you 5psi would only be at 6psi, which seems too low. Maybe I am not sure what the recommendation would be at the lower speeds.

I am thinking that maybe you should have added the DE to get a 1psi rise on a higher speed and be using that speed to decide when to backwash.

I run my pump on low speed most of the time, but flip it up to high speed to check the pressures.
 
Hmm. The manual that came with my filter says to wait until 8-10 psi above normal pressure. I am pretty sure my normal pressure at high speed around 2500rpm (which is not the highest ) is 10psi. It now reads 16.


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Also the reason I was adding de at the 55% is from reading it says to add it on low speed if you have a 2 speed pump so it can spread out better so I just done it at half speed on my ecostar.


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Since when do we agree with what the pool industry says :mrgreen:

The % change make a lot more sense to me since a fixed number can have a hugely different impact on the flow. How can a filter manufacturer know the head loss in your plumbing? If you have a low head loss and start a 8psi and wait for it to go up 8psi, that is 100% increase. If you have higher head loss and start at 16psi, waiting for 8psi rise is only a 50% increase.

In any case, the experts here have found that waiting more than about 20-25% pressure rise over the clean pressure results in a drastically reduced flow rate. So to maintain optimal cleaning we recommend it at the lower pressure.

I was not aware of the adding DE on low speed (I have never had to do it). So, seems like you did that correctly. I still think backwashing should be decided on high flow rate pressures though.

On low speed, my gauge barely registers a pressure.
 
Lol. Your right.

Ya mine on say 1200 rpm register like a 2. I think I am going to wait maybe an hour longer and backwash. See how the water looks tomorrow and add more de if the dirt is still not gone. It is already starting to look better though. Before I would brush and it would get terribly cloudy. Brushed earlier and it does not get anywhere near as cloudy.


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The pumps are typically not powerful enough the do any damage to anything due to high pressure. The pump could be damaged from overheating if flow completely stopped, but that is not possible from what you are taking about.

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Ok thanks! Pressure at 1800 rpm was 9.5 before 5 after backwash. At 2500 rpm pressure was 16 before. 9 after. Pressure on prime (3400 rpm) after backwash is 15-16. I will add more de tomorrow. There was a whole lot of dirt in there from grading last week so hopefully it will not rise so fast tomorrow. Thanks for you help!


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I can't say what pressures to backwash at. I'll let the experts figure that out for you. All I can tell you is that with my sand filter, if I'm adding DE (which I do fairly often) I have to backwash pretty much every day or two. It sure clears the water up but I do have to backwash quite often. I don't mind though, it keeps my CH and CYA levels in check.
It seems to go hand in hand. I use DE, I backwash a lot, and with fill water levels of CH so high, backwashing a lot allows me to keep my CH in range and I can even use tabs now and then if I feel the need to raise my CYA levels or I'm going away for a few days.
I can't begin to say how happy I am with the BBB method. My water is not just clear and clean, it's refreshingly crystal clear.
 
Backwash when you experience a 20-25% rise in normal pressure. Going beyond that is not very efficient.

You didn't say how you are vacuuming. My point was have you tried to vacuum the dirt rather than rely on your filter to pick it up. If you are relying on the filter, your current setting of 1800 doesn't have enough flow to do much good and the dirt simply resettles to the bottom before it can be removed from the water.
 
duraleigh said:
Backwash when you experience a 20-25% rise in normal pressure. Going beyond that is not very efficient.

You didn't say how you are vacuuming. My point was have you tried to vacuum the dirt rather than rely on your filter to pick it up. If you are relying on the filter, your current setting of 1800 doesn't have enough flow to do much good and the dirt simply resettles to the bottom before it can be removed from the water.
Click to expand...

When you say 20-25% are you referring to high speed or any speed?

I am rely on the filter to pick it up. I have a Polaris 9300 robot but it only filters 100 micros so it is not pick up this small dirt. I don't have a manual vacuum. I have been running main drain only and brushing it to the deep end. This morning there was a remarkable difference.


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25% regardless of the speed.

Without a vacuum of some sort, you will likely have a difficult time asking the filter to clean the pool floor....even if you stir it up with a broom. The problem is exacerbated when you run your filter on a very low setting.
 
It's a little more complicated than that, but not much. You should set your pump at a certain speed and record the pressure. Then whenever you want to see whether you need to backwash you should set the pump to the same speed and check the pressure again. And when it rises 25% at the same speed you should backwash.
 
But in this case their normal pressure was 5psi and after adding 1psi of DE they are at the backwash pressure. Thus why I thought a high speed might be better.

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duraleigh said:
25% regardless of the speed.

Without a vacuum of some sort, you will likely have a difficult time asking the filter to clean the pool floor....even if you stir it up with a broom. The problem is exacerbated when you run your filter on a very low setting.
Click to expand...

Ok thanks. I will look into getting a manual vacuum.


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