Return losing pressure every few hours. Only solved by backwash.

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C

Captainobvvious

0
May 23, 2015
32
Coventry, RI
I have an Intex sand filter. As far as I can tell there is no suction side air leak. There is no air in my pump skimmer basket or anywhere else I can see. There are also no bubbles in the return.

My pool is still milky light green so I was thinking since the return pressure issue corrected itself by backwashing it that the filter media was just really dirty. The water during the backwash is only very lightly discolored and only for a few seconds.

Is it possible the filter needs more sand? Before I take it apart I figured I would ask that question. If there isn't enough filter media then what is there could get clogged easily?

edit: I am SLAMming the pool and maintaining super chlorination levels as I try and clear the water up. The part that concerns me is the loss of return pressure but I am not sure if that is to be expected or if there is something wrong. It doesn't look like the backwash water is all that dirty.

I have an Intex sand filter on my 24' round metal frame above ground pool. Their 2150 gph saltwater system.
 
Everything you are describing sounds like you still have algae. No amount of backwashing will remove algae as it's now a live organism in the water. It needs to be killed permanently with the proper amount of chlorine (bleach) by following the TFP SLAM Process concept and using the [FC/CYA][/FC/CYA]. Of course you'll also need to perform frequent home water testing during the SLAM with either a TF-100 or Taylor K-2006C test kit (link below). If you have any questions about the SLAM Process technique, let us know.
 
I have been SLAMming the pool and it has improved quite a bit.

Would that account for the loss of return pressure/water flow?

For instance last night I let it run for a few hours after backwashing and it was running fine then when I woke up this morning it had very little water pressure on the return. I backwashed for a minute and the water ran very slightly discolored then when I turned it back to filter it ran great again.

This is to be expected during this process or is there something else I should be looking at?

I am patient with the water testing and the chemicals I just want to make sure there isn't anything else wrong.
 
Would that account for the loss of return pressure/water flow? For instance last night I let it run for a few hours after backwashing and it was running fine then when I woke up this morning it had very little water pressure on the return.
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That's a classic description of algae still in the water overwhelming the filter. Doesn't matter what kind of filter, they simply aren't designed to kill/remove live algae. Might be good at this point to see a full set of water test results. It can tell us a lot about your water. Seeing improvement is encouraging, but you have to follow the SLAM Process page to the "T" for it to work, and do it until you pass all 3 criteria.
 
Thank you

My most recent test from this morning

FC: 16 (I am bringing it a little higher because I work 10 hours a day and can't babysit it)
PH: 7.3
TA: 89
CYA: 1 (I have liquid stabilizer coming in today and will bring it up to 20 (during the slam and then up to 70-80 afterward) as per advice I have gotten on this site)

I just always worry there is something else wrong that's broken and waiting patiently is difficult for me during this. It makes sense that the filter is just overworked but does that make sense considering the water that comes from the hose during the backwash is pretty clear? That is me asking a sincere question not assuming I know more than you because I DO NOT!
 
The filter is doing its job. You have a big pool and a small filter so it is going to get dirty and need backwashing more frequently. Look at the pressure gauge just after you backwash and write the number down. Then when you see flow has reduced look at the gauge again and record that number. How much difference is there between the numbers? When pressure in the filter rises 20% over clean pressure it is time to backwash. Check your pressures every time you test the water. Look at the pressure first, backwash if needed, do your tests, top off water level in the pool if needed, then add your chemicals if needed.

The water in the pool will look much dirtier than a sample of the same water after it is pulled out of the pool. A sample of green, nasty water where you can't see the floor of the pool can look clear once it is removed from the pool. That is because light is better able to penetrate the sample. The smaller volume of the sample allows more light so it looks cleaner. Think of it like looking through an envelope. Away from the light you cannot see through it. Hold it up to the light and you may be able to make out the contents. Water coming from the backwash hose is the same way, once the solids are flushed out of the filter the pool water coming out of the backwash may look clear. Kind of an awkward explanation, but the filter is doing exactly what it is supposed to do.
 
Ha ha. Trust me, we all learn something here everyday. :) I suspect a big part of your problem has been that extremely low CYA. It should be 30 minimum for any pool. Of course you know a salt pool should be 70, but as you also know, you won't increase it to 70 until the SLAM is complete. Very good. But definitely make sure to increase the CYA to 30 for now which will help your SLAM. It will protect the chlorine much better from the sun and allow it to work better. I don't want to be too critical about your testing, as that TA of 89 seems odd. When we follow the Pool School - Total Alkalinity page, your results should be in increments of 10 (70, 80, 90, etc). Hopefully you are using a TF-100 or Taylor K-2006 test kit. It would be good to include that in your signature details as well so everyone doesn't ask you again later. :wink:
 
Texas Splash said:
I don't want to be too critical about your testing, as that TA of 89 seems odd.
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Sorry, I'm at work and posting to a forum trying to be sneaky sneaky and meant to type 80 not 89.

- - - Updated - - -

Darn pool store told me that I shouldn't add CYA until the pool was clear. I suspect they saw dollar signs flashing in their eyes as I carted out more and more liquid chlorine. I ordered the liquid stabilizer a couple days ago when I determined they were full of it.
 
Darn pool store told me that I shouldn't add CYA until the pool was clear.
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No worries. We'll coach you through it.
 

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We find that many times pool store employees primary goal is to sell stuff, not necessarily get your pool in perfect condition. As to whether that is because of improper training, lack of knowledge or just to sell stuff I will leave up to you. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their advice and testing.
 
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