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Thread: Sand filter backwash process

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    ChiknNutz's Avatar
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    Sand filter backwash process

    Hello, just looking to confirm or refute if I am going about this correctly. My process is based on instructions the previous home owner provided.

    1) Set valve to Backwash from normal Filter setting (he said 30 seconds, be we've found it better to go around 3 minutes)
    2) Set valve to Rinse (he said or to Waste, until reasonably clear on top site glass of sand filter). I'd say maybe a minute or two for the Rinse?
    3) Set valve to Waste (he said 15 seconds, but I've found if it's really dirty, need to go for about 30 seconds or it will blow back into the pool via return jets).
    4) Set valve back to filter

    My concern is that when set to Waste for that long, it seems to REALLY drain the water FAST, so I then have to refill with well water. Is it necessary to even use the Waste part of the process? I'm guessing so, or how else does the crud ever go away? I am not even totally clear what each step is actually doing within the filter, I can only guess.

    Second question related to sand filters. How often do you really need to replace the sand? We've been in the home for 3 yrs now, but we only get about 3 months of swimming so not nearly as lucky as you year-rounders get. Anyway, I have no idea if it's ever been replaced, nor do I know the real age of the pool. The filter is a Triton TR100 and the specs on it say 175# of 1/8"-1/4" of pea gravel and 400# of sand. If I use a filter cleaning chemical, does that help extend the life of it and really what is the anticipated life-span of the sand?

    Thanks again.
    Chris A.
    20x40 36k gal IG vinyl pool w/diving board & slide | 1.25HP Pentair Challenger motor & pump | 30" Triton TR100 sand filter | Pentair SM-20-3 multiport | Stenner 45MHP2 Peristaltic Pump & 13 gallon carboy (BBB) | Hayward CL200 Tablet Chlorinator (used on pool startup) | TF-100 | 2003 Sundance 850 Altamar hot tub

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    Re: Sand filter backwash process

    Backwash a couple minutes...........rinse for a minute........NO need to go to waste. Unless your filter pressure is gettin' high quickly your sand is probably fine. 5 years i understand is a good average.
    You do know to STOP the pump in between switching settings????????????
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
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    ChiknNutz's Avatar
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    Re: Sand filter backwash process

    Cool, thanks for the feedback. Yep, I was alerted to shutting the pump off before making any changes.
    Chris A.
    20x40 36k gal IG vinyl pool w/diving board & slide | 1.25HP Pentair Challenger motor & pump | 30" Triton TR100 sand filter | Pentair SM-20-3 multiport | Stenner 45MHP2 Peristaltic Pump & 13 gallon carboy (BBB) | Hayward CL200 Tablet Chlorinator (used on pool startup) | TF-100 | 2003 Sundance 850 Altamar hot tub

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    Re: Sand filter backwash process

    Set valve to Backwash from normal Filter setting (he said 30 seconds, be we've found it better to go around 3 minutes)
    Are you backwashing long enough for the sight glass to clear? How often are you backwashing?

    I have a somewhat larger version of that same filter.......you have a very good filter/pump combination for that size pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    ChiknNutz's Avatar
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    Re: Sand filter backwash process

    I backwash whenever the pressure gets close to 20 psig (per recommendation from previous home owner). Running pressue is usually around 13-16 and slowly climbs to 20 over a week or more. We haven't had the pool up and running for more than a couple weeks now since the new liner install, so most of the backwashing is a result of vacuuming or just general crud buildup from the initial fill-up this year.

    Glad to know this is a good setup, it looks like a good overall setup, though I am no expert.
    Chris A.
    20x40 36k gal IG vinyl pool w/diving board & slide | 1.25HP Pentair Challenger motor & pump | 30" Triton TR100 sand filter | Pentair SM-20-3 multiport | Stenner 45MHP2 Peristaltic Pump & 13 gallon carboy (BBB) | Hayward CL200 Tablet Chlorinator (used on pool startup) | TF-100 | 2003 Sundance 850 Altamar hot tub

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    Re: Sand filter backwash process

    That a good procedure for backwashing, too.

    There are varying opinions on the forum ranging from never changing to changing every 2-3 years.

    IMO, sand does not go bad. I have not changed mine in 7 years and never intend to. I do believe it needs to be inspected and cleaned yearly, however, and added to if it is below the correct level.

    It certainly could be that, by changing it out completely, you eliminate the need for cleaning.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Sand filter backwash process

    not to hijack but what do you mean by cleaning the filter annually? Are you talking of a chemical cleaner or is there a method of manual removal and cleaning of the sand?
    18'x24' (10,000 gal) above ground pool, 19" Proline sand filter (45 GPM), Jacuzzi 1.5 HP 2 speed pump

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    Re: Sand filter backwash process

    Funnily enough our original written instructions for backwashing say that you backwash for 30 seconds, but I am pretty sure this is not right - wonder where it comes from?

    We later learned that you should run on the backwash setting until the water in the sight glass is just about clear. In this part of the process the water is coming back up through the sand and going to waste, taking the crud with it. Until the water runs clear you still have crud in your filter.

    The rinse setting runs the water the right way again, cleaning out the lines and settles the sand back down, again with the water runing to waste. We also do this until the water in the sight glass runs clear, but this doesn't take long (30 seconds).

    The waste setting runs water from the pool lines direct to waste, bypassing the filter. I'm not sure how this can be part of the backwash process since it bypasses the filter. If you need to use it to avoid crud coming in at the return jets, then it might mean that you're not running for long enough on backwash or rinse.

    [EDIT - other reasons for the puff of dirt from the returns might be that the sand is channelled so it lets dirt right through, or that the pump is too powerful for the filter, again pushing dirt through. Am at the limits of my knowledge now - I've never seen dirt from the return jets in my pool.]

    Does this make sense? TFP experts, please shout if you think any of this is wrong.
    90k litres, outdoor in ground pool, concrete, painted (I hate paint)
    Sta-Rite 5P2R 1.5 Hp pump, undersized sand filter (needs upgrading).

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    Re: Sand filter backwash process

    what do you mean by cleaning the filter annually? Are you talking of a chemical cleaner or is there a method of manual removal and cleaning of the sand?
    With the filter still almost full of water, I remove the top and skim off any crud that I can find with an aquarium-type dip net or my hands.....I usually find quite a bit.

    Then, I take my hands and dig down in the sand, breaking it up, if needed, smoothing it and generally trying to fish out anything else that is embedded. My filter is pretty big so I cannot reach down to the laterals but obviously take care you don't damage them.

    That's it for me.....no chemicals. Usually takes me somewhere around 45 minutes or so, I guess.

    loop_pea,

    That's a very good explanation of the positions. I suspect OP is getting that puff of dirty water from not rinsing long enough.....it happens to me frequently as I hate letting all that water go.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    ChiknNutz's Avatar
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    Re: Sand filter backwash process

    I have to assume that plumbing a pool is pretty typical, so if that's the case, I was unaware that both the Backwash and Rinse events were dumping water to waste. I guess that is why I seem to lose a lot when I go thru my cycle of Backwash, Rinse and Waste. Looks like I can eliminate the Waste part. I thought I was imagining it, but I now recall seeing the water drop a little during the Backwash and just didn't know that it was in fact doing that so I dismissed that as a possibility. Really appreciate the explanation.

    The time-before-last that I did a backwash, I immediately performed a backwash after the pump had been off for a while after having put in some sequestering agent the night before. I turned the pump on to see the pressure, it was a little high, so I went straight to BW. When I did, LOTS of crud was in the sightglass...way more than normal and I was getting some junk back thru the return lines into the pool. I was horrified since the pool was looking really good, pi$$ed I was mucking it up again. I did one more BW routine and all was good, but it was odd the dirt blowing back in during BW that one time. On a couple other occasions last year, I didn't rinse long enough and then got a bit of dirt back thru the returns. I don't know how all the plumbing was done, so am not sure the mechanics of why that would occur. No big deal, I just like to know the WHY to everything.
    Chris A.
    20x40 36k gal IG vinyl pool w/diving board & slide | 1.25HP Pentair Challenger motor & pump | 30" Triton TR100 sand filter | Pentair SM-20-3 multiport | Stenner 45MHP2 Peristaltic Pump & 13 gallon carboy (BBB) | Hayward CL200 Tablet Chlorinator (used on pool startup) | TF-100 | 2003 Sundance 850 Altamar hot tub

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    Re: Sand filter backwash process

    You shouldnot get ANY water back thru the returns when the multiport is on backwash or rinse. If you are getting crud into the pool while you are backwashing, you may need to replace the spider gasket in the multiport valve.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Sand filter backwash process

    Quick update...I just pulled the top off of my multiport valve and the spider gasket is in fact TU. Two (2) of the "legs" have been sorta stretched out of the channels and are of course not sealing properly. I just ordered two new ones (one for a spare). Thanks bk406 for the insight as to what my problem might be.
    Chris A.
    20x40 36k gal IG vinyl pool w/diving board & slide | 1.25HP Pentair Challenger motor & pump | 30" Triton TR100 sand filter | Pentair SM-20-3 multiport | Stenner 45MHP2 Peristaltic Pump & 13 gallon carboy (BBB) | Hayward CL200 Tablet Chlorinator (used on pool startup) | TF-100 | 2003 Sundance 850 Altamar hot tub

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