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Thread: Flow problems after changing sand in filter

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    Flow problems after changing sand in filter

    I'm having a problem with the flow back into the pool. I noticed the PSI jumping north of 25 when it normally is around 15. Went and felt the returns and there was barely any pressure flowing into the pool. That was the morning of 6/7, since then I've backwashed/rinsed the filter 3 or 4 times over 24+ hours, each time achieving normalized PSI reading and thereby much improved flow from returns. However, a couple hours later the pressure builds and return flow dwindles. I recently changed the sand in the filter, is this normal for a length of time? If not, help?!?!?

    Some background...
    Last weekend, 5/31, I opened the pool for the first time (20+ year old pool, but first time pool/home owner) to pretty cloudy water. Had help dialing the chemical levels into normal ranges (except hardness) over the course of the week, and was told to change the sand in the filter by local Leslie's store (previous owner also confirmed sand needed changing sooner than later). So this weekend, 6/6, I did some research, drained the water, sucked out the old sand, discovered a broken standpipe inside, bought new standpipe/lateral mount/laterals, rinsed the filter body, screwed on drainage cap, insert the new standpipe/lateral manifold, filled 50% with water, covered standpipe opening, added 300 lb of Lighthouse brand filter sand (recommended by Leslie's.. the problem??), lined up multiport valve, re-bolted valve collar. Backwashed (2-3 min) and rinsed (1 min) with no leaking from filter (little from backwash hose fitting). Next morning, 6/7, come out to find PSI > 20 and barely any pressure from returns. Backwashed/rinsed filter, and saw improved flow. Added 25 lb of calcium stuff. Waited 6 hours later and then added Leslie's Clear Aid (to fix cloudiness). Checked late in the afternoon to find PSI > 20 and flow had diminished, backwashed/rinsed, and saw improved flow. Came out this morning, 6/8, to find PSI > 25 and barely any water pressure from returns, backwashed/rinsed, saw improved flow. Now convinced this can't be normal.

    ***I have emptied the skimmer and pump bucket constantly (even with minimal debris accumulation). Upon suggestions of a friend, I checked the pump impeller last night to make sure nothing was tangled up, and it was clean.
    18.5K gal, IG vinyl, hayward S244T sand filter, 1HP hayward super pump, hayward nat gas heater 250,000 BTU (2013)

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    Richard320's Avatar
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    Re: Flow problems after changing sand in filter

    Welcome!

    What does the water look like? How cloudy? Was it cloudy before you added the Hardness? If it's green or cloudy from an algae bloom, it will load up the filter in a hurry. Yes, as fast as an hour, even a sand filter. It will keep doing that until you kill the algae. No matter how much you filter out, more will just grow to replace it until you kill it all.

    Leslie's sells a lot of useless junk, but I'd give them credit to sell the right sand.

    Some other thoughts....
    1) Your vinyl pool doesn't need Calcium Hardness. There's no plaster to protect from leaching.
    2) If you hadn't bought the hardness increaser you didn't need, you also wouldn't have needed to buy the Clear Aid.
    3) The cloudiness is probably not just from the Calcium, but algae. You need to kill it.
    4) Don't go back to that same pool guy to get the stuff to kill the algae. You've just learned how they operate.
    5) When your filter is set to "filter" there should be no water coming out the waste pipe. None. You probably have a bad spider gasket inside the multiport valve. Before you tear into that, move the valve around a bit. There could be some bits of sand in there that just need to get dislodged.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Flow problems after changing sand in filter

    Hi Richard320, thanks for the quick reply, that is some insightful commentary!

    The water was cloudy and blue when I took off the cover on 5/31, way before I added the hardness. The water was going a greenish tint on me until I shocked it on 6/2. It's now a blue color for sure, but still really cloudy (can't see main drain in 6 ft deep end). So you think that if I kill the algae, that will help the problems with the flow from the returns/pressure in the filter?

    I think I misrepresented the multi-port valve functionality... after I replaced everything, it seemed like the clamp around the waste opening that held the backwash hose wasn't doing a great job of sealing it 100%. I have one of those thin blue backwash hoses and the metal circular clamp you tighten with a screw, so I had a little bit of leakage there but nothing crazy.

    [side note] In fact, the water was slightly cloudy towards the end of the season last year (Oct), but I paid a company to come close the pool and figured they'd address it before closing if necessary.

    The chlorine levels were OK based on the water test Leslie did, the algae can still live in that? I use chlorine tabs, but was hoping to install a chlorinator this season.
    18.5K gal, IG vinyl, hayward S244T sand filter, 1HP hayward super pump, hayward nat gas heater 250,000 BTU (2013)

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    Re: Flow problems after changing sand in filter

    The chances are your filter is doing exactly what it is supposed to do....catching debris, clogging up, and requiring you to back wash it.

    What's abnormal is the debris that you have and that is a chemistry problem.....not a filtration problem

    Everything going forward from here is all about test results. Wed can help you get your water crystal clear but you are going to have to be able to test your own water and take charge of managing your pool. It's really pretty easy and we'll help you every step of the way.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Richard320's Avatar
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    Re: Flow problems after changing sand in filter

    Quote Originally Posted by djbloodfiya View Post
    The chlorine levels were OK based on the water test Leslie did, the algae can still live in that? I use chlorine tabs, but was hoping to install a chlorinator this season.
    There's Leslie's again....

    You probably have astronomical CYA from feeding the pool pucks and "shock." I believe they say something like 30-200 is "OK." It's not. Just to keep a clear pool staying clear at 200 CYA would require FC levels of 15-20. The preprinted sheets say 3 FC is "OK" No, it's not. Not if CYA is above 30. To kill Algae at 200 CYA would require 79 FC for several days. Pool School - Chlorine / CYA Chart What's your CYA? Do you trust their test results? What's your FC? You might not be anywhere close to killing algae, let alone keeping it at bay.

    Something I wrote a couple years ago that might explain what you're up against. Some of my best writing.
    We'll take a 16000 gallon pool, because that's what I have. On a fresh fill, prominent national pool chain recommends 2.5 pounds pf stabilizer per 10,000 gallons, which works out nicely to 4 pounds which brings CYA to 30.

    With an average loss of 2 PPM/Day or 14 ppm/week, I'll have added 8.6 PPM/CYA if I used trichlor pucks perfectly. And they recommend a weekly "shock" of dichlor between 5 and 10 FC.... 2-3 oz per 10,000 gallons. Split the difference; I'll add 4 oz. CYA went up another .9.

    So..by the end of week one, I have added 9.5 more CYA. It is now 39.5. Mimimum FC for that is 3, so I'm probably okay.

    Week two, up to 49 CYA.
    Week three, 58.5. Minimum FC should be 5, but they recommend 3 as ideal, so the pool looks a bit hazy. So I'll toss in a little extra dichlor "shock" to jack FC up to 10. Which adds another 6.4 CYA. Keeping count? We're up to 64.9 now.

    That caught the algae just in time.. we had two weeks of good luck. A steady diet of pucks and 4 oz. "shock" each week only added another 19, up to 73.9 now.

    Week 6 it started looking funky, so we "shocked"it once again. CYA is up to 99.3. But minimum FC to keep algae at bay is 8, and we're still holding things to 3, because prominent national chain's preprinted sheet shows that as ideal. So algae got a toehold and the pool has a bit of a tint. So we throw two whole bags of dichlor in which jacks it another 7.6 by the time week 7 is over, we're at 116.4, because we had pucks in the floater the whole time.

    So...in 7 weeks, from 30 to 116.4. Let's say there are no more algae outbreaks because they sold me a huge bucket of phos-free and another of yellow-out monopersulfate "shock" Nothing but the pucks and the extra 4 oz of dichlor "shock" weekly. So the next 7 weeks added 66.5, which brings the total to 182.9 CYA.

    Now if we didn't understand this and things looked a bit hazy, we might throw an extra puck or two in the floater every couple weeks, which will drive it over 200 easily.

    And then next year when you try to open, you're whining here how you "shocked" it and it's still green. And then you get indignant at the cost and bother to drain 3/4 of the pool. Seen it over and over and over and over here.
    Your situation is not unique at all. Stay away from Leslies and get a proper test kit and take control of your pool and your wallet.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Flow problems after changing sand in filter

    Quote Originally Posted by duraleigh View Post
    The chances are your filter is doing exactly what it is supposed to do....catching debris, clogging up, and requiring you to back wash it.

    What's abnormal is the debris that you have and that is a chemistry problem.....not a filtration problem
    That is very reassuring. After all the hoops I jumped through with the filter, wanted to make sure I wasn't damaging the equipment.

    Quote Originally Posted by duraleigh View Post
    Everything going forward from here is all about test results. Wed can help you get your water crystal clear but you are going to have to be able to test your own water and take charge of managing your pool. It's really pretty easy and we'll help you every step of the way.
    I have a kit at home, I will take the results tonight and post them. But here's what Leslie's readings said as of 6/7:
    pH: 7.6
    Total Alkalinity: 90
    Cyanuric Acid: 30 (which I thought was a little weird too per Richard320's comments, but I probably added 4 or 5 inches of water between hose and rainfall in the last week)
    Calcium Hardness: 120 (prior to adding 25 lb on 6/8)
    Total Dissolved Solids: 400

    I have the chlorine and pH kit at home that I'll post the results of tonight.
    18.5K gal, IG vinyl, hayward S244T sand filter, 1HP hayward super pump, hayward nat gas heater 250,000 BTU (2013)

  7. Back To Top    #7

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    Re: Flow problems after changing sand in filter

    Just took my readings earlier this evening:
    pH - 7.5
    Free Chlorine - 1.0

    The filter seems to be taking longer to reach the > 25 PSI range, so I've only had to backwash once today. Still not sure if this is the new normal? I didn't have to backwash daily last season...

    The water is still blue, and getting clearer little by little it seems. Since the Free Chlorine was a little low, I added two bags of shock after the sun went down, hoping it'll clear up in the next day or so??
    18.5K gal, IG vinyl, hayward S244T sand filter, 1HP hayward super pump, hayward nat gas heater 250,000 BTU (2013)

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    Mod Squad pooldv's Avatar
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    Re: Flow problems after changing sand in filter

    Welcome to TFP!

    FC is not a little low it is below the minimum level for your CYA which will allow algae to grow which will cause your filter to clog up daily. Next the pool will get cloudy and slimy and then it will turn green. Be careful with what is in the 2 bags of shock. It could be adding lots of CYA or calcium to your pool. TFP prefers to use liquid chlorine (usually 10-12%) or bleach which is liquid chlorine that is usually 6-8.25% chlorine.

    It is very important not to let your chlorine level drop below the minimum level for your CYA ever. Maintain chlorine level at target, I prefer 1-2ppm higher than target personally, according to the Pool School - Chlorine / CYA Chart

    Use Poolmath to calculate how much chlorine to add to get your pool to the correct ppm.

    To validate if you have algae in your pool you can get your chlorine level up to 10ppm and Pool School - Perform the Overnight FC Loss Test (OCLT)

    If you do have algae then you will need Pool School - SLAM - Shock Level And Maintain
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    Re: Flow problems after changing sand in filter

    Just to close this thread, the crazy PSI issue dissipated over time, I think it was just the new filter media needing some time to be worked in.
    18.5K gal, IG vinyl, hayward S244T sand filter, 1HP hayward super pump, hayward nat gas heater 250,000 BTU (2013)

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    Agent99's Avatar
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    Re: Flow problems after changing sand in filter

    ..or the gauge itself had some issues. Sometimes flicking it with your finger helps. It might have has something lodged inside it or at the opening and sometimes needles just stick.
    ----Chris----
    25k IG/Spa Figure 8, 18x36, Pebble Sheen Blue Granite, Sta-Rite S8M150 Cartridge Filter, Pentair 460805 400k BTU Heater & 011018 IntelliFlo VarSpd
    Liquidator, Fafco Solar Heat, Polaris PB460 Booster Pump w/280 cleaner, Katchaleaf Cover, TF100 Test Kit, FAKE MAIN DRAIN

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