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Thread: Sand filter high pressure

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    Angry Sand filter high pressure

    Recently purchased home with a pool and have had some "smaller" issues that I have a warranty company deal with (might be a mistake). After 1 pump motor change out, the pump lost prime and "melted" the impeller (I didn't see it). They replaced the impeller and noticed that the pressure on the sand filter was high(=30 psi). Wanted to charge me $500 to change out the sand. Needless to say, I first replaced my pressure gauge and it works fine. I then changed out the sand myself. It did have some gray material in it but it was not the source. Since I don't know when the sand was last changed, I changed it myself. Once it was all back together, I still have 30psi on the sand filter and a green pool to boot. I think that the impeller that was put in might be the wrong size and the guy was a con. Any other ideas on the high pressure? I am about to check into the impeller on both pumps to compare them.

    thanks for any comments!

    13,000gal SWG in ground gunite pool with elevated spa and water feature.
    2.2 hp whisperflo pumps (x2) and booster pump for Letro legend.
    TR-100 sand filter. TF-100 testing kit.
    Pool owner since 10/2015. (Houston, TX area)

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    Mod Squad Bama Rambler's Avatar
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    Re: Shad filter high pressure

    If they put too large an impeller on the pump it would trip out the motor.

    How is the flow out of all the returns?
    How many returns do you have?

    I suspect the pressure is high because of the algae bloom.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Sand filter high pressure

    Welcome to the forum. I agree with bama.
    I still have 30psi on the sand filter and a green pool to boot.
    It is fairly common to believe filtration is a big factor for having algae. It has VERY little to do with it. Algae is a chemistry issue and must be dealt with through chemistry and then the DEAD algae can be filtered from your pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Sand filter high pressure

    Quote Originally Posted by duraleigh View Post
    Welcome to the forum. I agree with bama. It is fairly common to believe filtration is a big factor for having algae. It has VERY little to do with it. Algae is a chemistry issue and must be dealt with through chemistry and then the DEAD algae can be filtered from your pool.

    So your advice is to address the pool chemistry first (while the filter is showing high pressure) and then once the pool is clear, the pressure on the filter will drop back to normal levels (after proper filter back flushes).

    i will also check the return nozzles as well..... After Christmas lunch😳.... Will let you know how the cleaning goes. Thanks for the help and Merry Christmas!

    13,000gal SWG in ground gunite pool with elevated spa and water feature.
    2.2 hp whisperflo pumps (x2) and booster pump for Letro legend.
    TR-100 sand filter. TF-100 testing kit.
    Pool owner since 10/2015. (Houston, TX area)

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    Mod Squad tim5055's Avatar
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    Re: Sand filter high pressure

    Quote Originally Posted by monutt View Post
    So your advice is to address the pool chemistry first (while the filter is showing high pressure) and then once the pool is clear, the pressure on the filter will drop back to normal levels (after proper filter back flushes).
    As you recently purchased the home, how are you determining what the "normal levels" should be? There are many factors involved in what eh pressure ends up being including the filter, how the pipes are run, how many returns, the size of the returns and many other things.

    The changing of sand in a sand filter is almost never needed. A deep clean yes, change - no.

    Yes, lets get the algae cleared up. We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use.

    While you wait for it to get delivered, you have a homework assignment. Start with Turning Your Green Swamp Back into a Sparkling Oasis
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Sand filter high pressure

    You have been given excellent advice. The most important right now is ordering a reliable test kit. Read the ABC's of Pool Water Chemistry so you'll understand everything.

    Welcome to TFP and Merry Christmas!
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Sand filter high pressure

    It has been a couple of weeks but I am happy to say that we have a blue clear pool again. I did order the tf100 test kit and will use it going forward. I also have found some of the pressure issues but still need some assistance.

    As I treated the algae issue, the pool sand filter pressure read nearly 30-31 Psig the entire time. It would appear that the pressure issue was not a function of the algae. I took out my saltwater chlorine generator (SWG) and it was plugged with debris. Once I cleaned that off, the pressure dropped nearly 10 psi. The first 1-2 months we took over the pool, I recall a pressure more like 10-12 psig.... So I would like to work down to that level again. I have since watched my pressure rise to 31 psi again and cleaned the SWG for it to return to 21 psi (this keeps occurring). Today, I went looking for the source of the debris in a troubleshooting exercise. I used one of those hose bladders to help direct the flow of water and opened us different points to see if the debris came out. I went from the sand filter sliding gate valve down under ground and back up to my heater inlet... Nothing but water. I went from the same valve through the heater to its outlet... Nothing but water. I went from the valve through the heater to the spa/pool 3-way valve.... Nothing but water. I went from the valve through the heater, 3-way valve to the SWG..... Nothing but clean water????? The only part downstream of the sand filter that i have not tested is the sand filter outlet pipes that collect the water in the bottom of the sand to the sliding gate valve. The debris is kind of small stuff like it might make it through the pump suction screen and collect on the SWG parellel plates but definitely not through the sand filter!!! So again, I am at a loss. I will start to monitor the SWG on a set frequency to see how fast it builds up over the next couple of weeks. All that said and once it is "clean" it still has 21 psig which is too high for me! I plan to take off the return nozzles to clean them out and blow them back next. I also have some small air leaks in the system as I see/hear bubbles coming out of the returns. Pump seems to be maintaining prime but the spa is slowly draining down overtime. Those could just be additional issues but trying to share all things that I am seeing no matter how small.

    Thanks for for any comments!

    13,000gal SWG in ground gunite pool with elevated spa and water feature.
    2.2 hp whisperflo pumps (x2) and booster pump for Letro legend.
    TR-100 sand filter. TF-100 testing kit.
    Pool owner since 10/2015. (Houston, TX area)

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    Mod Squad pooldv's Avatar
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    Re: Sand filter high pressure

    The SWG can emit small bubbles from 1 or 2 of the returns closest to the pump when operating. See if they are still there when it is off. Have you ever done a deep clean on your sand filter? Maybe it's time to get dirty, Deep Cleaning a Sand Filter
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    Re: Sand filter high pressure

    How did you "treat the algae issue"? Did you follow the full SLAM Process?

    What you are describing (filter goes up to 31, backwash and it drops to 21) is the normal operation of the sand filter as it collects debris. If you did not kill, but merely stunted the algae colony in the pool a constantly clogging filter is a common complaint as it catches the free floating algae in the water.

    Clear water does no mean no algae. The only way to prove all the algae is dead is the test at teh end of the SLAM -




    • CC is 0.5 or lower;
    • You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
    • The water is clear.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Sand filter high pressure

    I will check on the swg creating bubbles... Thanks for that suggestion.

    I just replaced all the sand in our filter with new. That was before we treated the algae bloom. Do you think I still need to do the deep clean? Same pressure before and after sand change out.

    - - - Updated - - -

    We will conduct those tests to confirm. Thanks.

    The comment about the 31 to 21 psi drop was after we pulled and cleaned the swg chlorine generator and not when we conducted a back flush. We see no change in pressure after a back flush. When I am conducting a back flush, the pressure drops to 6 psig. I think that is the pressure drop in the sand filter with the additional 15 psi coming from somewhere else?

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    Mod Squad tim5055's Avatar
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    Re: Sand filter high pressure

    Quote Originally Posted by monutt View Post
    I will check on the swg creating bubbles... Thanks for that suggestion.

    I just replaced all the sand in our filter with new. That was before we treated the algae bloom. Do you think I still need to do the deep clean? Same pressure before and after sand change out.

    - - - Updated - - -

    We will conduct those tests to confirm. Thanks.

    The comment about the 31 to 21 psi drop was after we pulled and cleaned the swg chlorine generator and not when we conducted a back flush. We see no change in pressure after a back flush. When I am conducting a back flush, the pressure drops to 6 psig. I think that is the pressure drop in the sand filter with the additional 15 psi coming from somewhere else?
    How did you treat the algae??

    Another thing is some "magic" chemicals sold by pool stores can clog the sand.

    Let us know all the products you have put in the water.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Sand filter high pressure

    After a couple of weeks, I have more data to share. To address a few questions, we treated our pool using the SLAM methods provided on this site. We have an elevated FC level from that process but we have passed all the tests to show that the algae bloom is done. Pool has been crystal clear for weeks now. I have allied no other chemicals/cleaners to my pool. I have now been cleaning/clearing out the swg once a week (three times so far) as it seems to be acting as a filter and building up 10 psi over baseline (in 6-7 days). The question I have is: how is this material (plant like stuff....big enough to get caught up on the parallel plates in the swg) getting to it? It is on the outlet of the sand filter so it should not be getting to it... But it is. I have taken apart every fitting from the sand filter outlet to the swg and flushed it with water with no material found. I thought it would just work its way out and I would be done with it but it keeps building up. Thoughts or other questions??? I will try to follow up sooner.... I have just been collecting data since my last update.

    13,000gal SWG in ground gunite pool with elevated spa and water feature.
    2.2 hp whisperflo pumps (x2) and booster pump for Letro legend.
    TR-100 sand filter. TF-100 testing kit.
    Pool owner since 10/2015. (Houston, TX area)

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    Mod Squad zea3's Avatar
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    Re: Sand filter high pressure

    Could you please post some pictures of the plumbing pad for the pool? We would need some shots of the whole equipment pad and some slightly closer shots of the plumbing between the pump and filter and the filter and the pool. Also include a shot of the multiport valve on the filter.
    TFP Moderator
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    Re: Sand filter high pressure

    I don't think we have ever had an issue as you describe posted on the forum.

    Rather than flailing at it with wild speculation, post up some good pics......that'll help

    I would like to see the stuff clogging the SWG....both imbedded in the SWG and then perhaps laid out onto a white sheet of paper.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Sand filter high pressure

    If you have a slide valve instead of a multiport, you can't rinse after backwashing. That will allow some debris to get downstream. A multiport would be a better choice. Backwashing until the water is really clear at the sight glass will help.

    If you're not getting sand back in the pool, I would suspect that the slide valve or multiport is allowing debris to bypass or the filter's internal air relief is missing the screen.

    Also, the pump is oversized for the pool.

    Try this: Pour about a pound of de in the skimmer while the pump is on and watch the returns for a few minutes to see if any get past the filter.

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    Re: Sand filter high pressure

    I looked through this thread and did not see any chemistry test results posted. Those values and pictures of the pool equipment will aid in helping you troubleshoot your pool.
    In ground, 14,000 gallon, white plaster, unheated, stone waterfall, DE Filter, Rainbow 320 Cl, Polaris 3900, FloVis flow meter, F100 test kit, Circupool RJ30+ SWG, Circupool VJ1/Speck Badu EcoM3V variable speed pump.

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    Re: Sand filter high pressure

    I must apologize for the significant delay in response. I would like to share what I finally learned about my filter pressure issue. Again, thanks to all for the suggestions. I want to close out this issue just in case anyone else has this problem in the future.

    If you remember back, I posed that a pool repair company did some work on my system and told me that I needed to change out my sand in the filter.... well, One of the first things I did was pulled out my sliding valve on the filter that allows me to backflush it. It looked fine and then I moved on to other possiblities. As frustration builds, I pulled it again just going over everything. At first I didn't notice it but the bottom plunger was broken off. When you looked at it, it was broken off flat so it didn't look like it was missing anything. I pulled a picture of one and then noticed that it was gone. I went back to my piping looking for the broken piece to be down in the pipe.... it was not there.... if it broke while in operation, it should have been in the pipe. The only conclusion is that it got broken by the pool company and they didn't want to replace it. Wanted to hid the value ina the expensive sand filter change out. This explained the high pressure and debris as the Filter was effectively being bypassed. Since I replaced it, everything is back to a more normal pressure 20 psi, my swg is not acting like a filter, and my I can only blame myself if my pool is not crystal clear. Again, thanks for all your help over these weeks/months. I hope none of you run into this issue the way I seem to have but you could shear off the valve bottom and see similar results. Hope this helps anyone in the future!

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    Mod Squad YippeeSkippy's Avatar
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    Re: Sand filter high pressure

    Wow, interesting. Thanks for sharing and giving us the heads up if this comes up again.

    Just for future reference as I read the previous posts you wrote- Sand rarely *ever* needs changing out. Only on odd occasions such as converting from Bacqua to chlorine. Sand just doesn't "wear out".... it may get dirty. In that case you clean it out (directions found on TFP) but no need to buy more. $500!? OUCH!!

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