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Thread: De backwash procedure, am I overreacting?

  1. Back To Top    #1

    De backwash procedure, am I overreacting?

    I don't really feel like I can explain the situation in a short paragraph, but I got a message saying the post was too long, so here's the gist. Apparently my filter pressure was at 32, the new service backwashed for 1 minute, then, according to their standard practice, added "2lbs DE per 30 seconds of backwash" - not surprisingly, pressure is still high. This seems odd to me, odd enough that I feel like they don't know how to handle a DE filter properly. Is this "DE calculated per 30 seconds of backwash" familiar to anyone? Full issue below.

    My apologies, I had typed a long and well detailed post, but I'm on mobile and it got erased -_-. I'll answer any questions you may have, but my issue is below.

    I've had my pool for 3 years and recently moved internationally. I have a 48sqft Hayward, with markers on the pressure gauge around 10 and 20, which is the regular window. Ive never seen the pressure over 26-27. I'm renting the house out (no tenant yet) and have a pool service. I was still in town for the first service, where I had some concerns because they left the filter running at high pressure and put pucks in the skimmers rather than the inline chlorinator. They offered explanations that seemed reasonable, if a bit odd, so I let it slide. After their second visit, they recommended a filter disassemble and clean, which I usually do once a year around November. I knew it was close, so not a shock, but I just gave them a decent amount of money for other things and paying in advance for maintenance ($40/week), so I wanted to put it off at least a few weeks to see how their service goes. I asked some questions, and this is where concern s were raised. I'll just paste correspondence below, I had asked if we delay the clean, would they continue to maintain pressure by backwashing, he gave a non-answer, and I'm starting with my response:

    Me: Has the filter been backwashed by your techs, or simply continued to run at raised pressure?
    And again, if we delay the full clean, will your tech backwash the filter, or leave it to run at high pressure?

    Him: It has been back washed, it's still that high. When filter pressure is over 25, they automatically backwash.
    Again, we recommend filter cleans twice per year. Since it's been since November since you've had one, we recommend another one.

    Me: Did backwashing not reduce the pressure below 25 at all? How much DE was added in recharge?
    I know what you are recommending, thank you. You can understand, as I'm not able to see the filter myself, what you're describing, or what it seems you are describing, sounds a bit odd, as it's a large change from where the filter was while I was working with it only a few weeks ago. I have never seen it reach as high as you are stating, even just prior to the last full clean.

    Him: Psi was at 32, back washing for one minute only reduced to 25. Therefore filter clean is needed. DE is added by time, one scoop per 30 seconds of backwash.

    Me: This answer concerns me. This is not a method I have ever used or heard of. Among other issues, a very short backwash period to begin, this method also does not account for filter size when recharging.
    Typically I backwash until the water comes out clear, then rinse about 30 seconds, and repeat that process about 3-4 times. I then add 4-5 scoops of DE to replace. This process layout can be seen in the following link, it is the process recommended by nearly every source I can find - How to Backwash DE Filters.
    Can your techs simply maintain this backwashing process?

    Him: This is probably why your filter is at high psi.
    If you backwash weekly, 30 seconds is all that is required to backwash. As I said.
    A DE scoop holds an average of 2lbs dependent on powder compound. If you're adding 4-5 scoops of DE after backwashing then you've added 8-10lbs of DE. A full charge on a 60ltr DE filter is only 6lbs, one pound per 10 sq ft of filter.
    If you add too much you will clog the system, reduce the flow rate which in turns causes algae.

    Me: Perhaps your scoops are different than mine. The blue scoop that I use holds just about .75lbs of DE - it's a standard blue scoop from Leslie's.
    What concerns me is that if your scoops are 2lbs, you added 4lbs of DE to my 48sq/ft (requires under 5lbs total) filter after backwashing for only one minute. Is that how much you put in it?

    So this is where were at now, he stopped responding after that. What I'm looking for here is your opinions. To me, I feel like this guy has no idea what he's doing. As much of a pain as it will be to handle from 5000 miles away, I feel like I should be looking for a new pool service. Does my pool need the service he's recommending? Sure, but I don't think as urgently as he's saying, and in the course of him "selling" it, to me at least, he's shown me that he doesn't really know what he's doing. Then again, 3 years ago I knew nothing about pools, so I'm no expert.

  2. Back To Top    #2

    Join Date
    Jun 2016
    Oklahoma City, OK

    Re: De backwash procedure, am I overreacting?

    The PB was correct in recommending a filter clean as a result of gauge readings. And filters generally do need at least two cleans per year. However his recharge method is a bit odd, indeed. I for one, follow your method in adding DE not this "time" method he was describing. It sounds like he messed the filter up by overdosing and it needs to be cleaned ASAP to rectify since the pressure is reaching over 30 and not dropping below 25 as stated. U could have a different PB go by to verify the original PB claims

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    Join Date
    Jul 2012
    Dallas, TX

    Re: De backwash procedure, am I overreacting?


    My DE Filter experiences are different than what the forum recommends. This thread may provide some info about backwashing techniques. I posted my info in that thread (post #14).

    Since posting in that thread, I recently backwashed on 08/20/16:

    Prev BW: 04/18/16 18 wks ~4 mo
    PSI before BW: 26
    PSI after BW, before charging w/new DE: 12.5
    PSI after charge: 13.5
    GPM Flow Meter before BW: 33 After: ~55

    My 'best-case' GPM flow, with the Multiport Valve in 'Recirc' position (bypassing the DE. Filter) is about 58.

    My best-case 'clean' PSI is ~12. This is the PSI reading after either completely cleaning my DE Grids or installing a new Grid Assembly.

    Since my 'clean' PSI has only risen ~1.5 PSI since my last filter clean (pull Grids, clean, re-install), I have not replaced/cleaned my Grids on a timed basis since the last time I replaced the Grids with my spare assembly on 09/18/13 .

    I realize this isn't forum-recommended procedure but I'm continuing this method as it's been working good for me since I switched to TFP pool methods (FC / CYA ratio dosing) in June '14.

    You mentioned the Leslie's blue DE scoop:

    DE Scoop.JPG

    The scoop actually measures 5 Sq Ft coverage of D.E. which is equal to approx. lb. For example, I have a 36 Sq Ft Nautilus (now part of Pentair's product lines) D.E. Filter. The filter manual specifies 3.6 Sq Ft DE charge.

    When I charge a completely new or cleaned DE Filter Grid assembly, I'll use 7 scoops with the Leslie's blue scoop which is equal to approx. 3.6 Sq ft (actually 3.5).

    After Backwashing, I use the "80%" rule, which refers to charging a typical DE filter with ~80% of the rated DE charge since Backwashing doesn't remove all of the old DE inside the filter.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

  4. Back To Top    #4
    Mod Squad zea3's Avatar
    Join Date
    Jul 2009
    Houston, Texas

    Re: De backwash procedure, am I overreacting?

    You may want to contact other pool services and interview them over the phone as to how they conduct routine maintenance such as backwashing and using pucks. To me putting pucks in the skimmer is not only detrimental to the pool, but lazy as well, especially when you have a working inline chlorinator. Do you have a neighbor who can keep an eye on things and report back until the home is leased?
    TFP Moderator
    Helpful links: TF Test Kits,TFP Pool School, PoolMath
    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
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  5. Back To Top    #5

    Re: De backwash procedure, am I overreacting?

    Sadly, no neighbors that can watch it, the ones we actually know travel a lot themselves and are gone for a while.

    My parents still live about 30 minutes away, so they've gone by to check on things, but they have no idea what they're looking at with a pool filter.

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