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Thread: Max pressure 20PSI? cmon!!

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    Max pressure 20PSI? cmon!!

    I used to get pressures in the high 20's before I would clean the filter and replace the DE. I have a 1H.P. pump connected to a Haward EC-50. No visable signs of air in the pump strainer or at the pool jet. (above ground pool) Does anyone know what the max output pressure should be from a Power flo sp1580 1 hp pump? Not gpm or other type of flow ratings but what is the max pressure that this pump should put out if it is completely obstructed at the discharge. Thank you.
    rgil
    15000gal. IG/attached hot tub
    quartz plaster
    Pentair DE filter
    2HP whisperflo pump

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    Mod Squad JohnT's Avatar
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    Re: Max pressure 20PSI? cmon!!

    Welcome to TFP.

    You'd probably see 35 or 36 psi with the outlet blocked. Low filter pressure is usually better than high. The real thing to be concerned with is flow. If the flow from the returns is strong and the filter is keeping the water clear, the lower the pressure the better.

    Is this an AG or IG pool? Cleaners/Heaters/Chlorinators?
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Max pressure 20PSI? cmon!!

    Quote Originally Posted by JohnT
    Welcome to TFP.

    You'd probably see 35 or 36 psi with the outlet blocked. Low filter pressure is usually better than high. The real thing to be concerned with is flow. If the flow from the returns is strong and the filter is keeping the water clear, the lower the pressure the better.

    Is this an AG or IG pool? Cleaners/Heaters/Chlorinators?

    That is what I would think should be the max pressure for this pump. It is an AG 28' round and there is a chlorinator. What I'm getting is 20psi (start pressure is 16psi clean) after about 2 hours of operation. Once it hits 20 I get hardly any flow. I mean you can't see any disturbance in the water but if you put your hand in front of the jet you can feel water coming out a little.
    rgil
    15000gal. IG/attached hot tub
    quartz plaster
    Pentair DE filter
    2HP whisperflo pump

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    Mod Squad JohnT's Avatar
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    Re: Max pressure 20PSI? cmon!!

    Quote Originally Posted by rentalwhitehemi
    That is what I would think should be the max pressure for this pump. It is an AG 28' round and there is a chlorinator. What I'm getting is 20psi (start pressure is 16psi clean) after about 2 hours of operation. Once it hits 20 I get hardly any flow. I mean you can't see any disturbance in the water but if you put your hand in front of the jet you can feel water coming out a little.
    That sounds normal for either dirty water or a filter that needs to be disassembled for cleaning. The pressure change is the only thing to be concerned with, and when you see 4psi change it means your filter is restricted. I'm not sure why you are concerned with the max pressure of the pump. It has no bearing on what is going on with your filter.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Max pressure 20PSI? cmon!!

    UPDATE: I started the pump at 9am yesterday, after soaking the fingers in a liquid filter cleaner solution overnight. The start pressure is the same (16 PSI) and when I checked the pressure at 6pm it climbed up to 18 PSI. Flow was strong and I was kind of happy. I would have liked to see the pressure stay the same or maybe only jump 1 PSI. Especially after the soaking and new DE in the filter and crystal clear water. I didn't touch the filter until 11pm when I noticed that I was back where I started. 20 PSI and no flow.

    I'll try this again. I have worked with various types of pumps that pump filtered and nonfiltered liquids. In each application, the principle is the same. When the liquid is flowing and the filter is clean and there are no obstructions, you have a normal pressure. In this case, I will say that the normal pressure is 16 PSI. When an event occurs that causes any one of these conditions to change, the pressure will change. For example; if you have a pipe burst, you lose pressure. If you get an obstruction of any kind, be it partial or complete, the pressure will rise accordingly. Does anyone disagree with those statements? If so stop reading.

    This pump has run much better in the past. The normal pressure has been the same as it has in the past 4 years and up until now, the pressure would climb to 25-28 and the pitch of the motor's sound would change and I still had plenty of flow. In fact, I could still vacuum under those conditions. Mind you that this is after weeks of running 24/7 before the pressure would climb to this level.

    Now with crystal clear water with good levels on the test strip ( hardness, total chlorine, free chlorine, Ph, Alkalinity) The pressure climbs to 20 PSI (4 PSI increase) after 12 hours of operation with new DE and a freshly chemically cleaned filter. And the flow is reduced to zero gpm. Sounds like a complete obstruction to me. This motor should be screaming to the point that you think that the filter is going to explode. The pressure should be well past 30-35 if there is a complete obstruction on the discharge side of the pump and the pump is not sucking air. Mine is not sucking air by the way, before somebody asks me that.

    What I was hoping to here was something like " you need new seals or a new motor or have the motor rebuilt" or something. There must be someone in the pool world that has come across this before and found a fix. But don't tell me that a max pressure of 20 PSI when I have 0 gpm is irrelevant.
    rgil
    15000gal. IG/attached hot tub
    quartz plaster
    Pentair DE filter
    2HP whisperflo pump

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    spishex's Avatar
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    Re: Max pressure 20PSI? cmon!!

    A max pressure of 20 PSI when I have 0 gpm is irrelevant.

    Just kidding. Check your impeller for debris.

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    Ohm_Boy's Avatar
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    Re: Max pressure 20PSI? cmon!!

    Check your impeller for debris
    ...or slippage
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

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    Re: Max pressure 20PSI? cmon!!

    Quote Originally Posted by rentalwhitehemi
    But don't tell me that a max pressure of 20 PSI when I have 0 gpm is irrelevant.
    Assuming you actually have 0 GPM, the maximum head of the pump is then 46'. However, maximum head for a 1HP Superflo is about 65' (28 PSI) so either something is wrong with the pump or flow rate is higher than 0 GPM.

    Also, if the filter PSI rises in a very short period of time, it is either a filter problem or you have something in the water that is getting filtered out (algae). Are you sure your not fighting an algae bloom? Check your cc.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Max pressure 20PSI? cmon!!

    I predict algae as the answer. Testing with test strips is inadequate.

    That you start at a normal pressure and then it rises would seem to mean that something is clogging the filter as the water is circulated thru it. My bet is posting a full set of test results will result in FC too low and perhaps some other problems.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Max pressure 20PSI? cmon!!

    I'm with Dave on this one! The filter is removing SOMETHING from the water which is why the pressure is rising.
    Also, have you tried changing out the pressure gauge to make sure that the pressure is really maxing out at 20 psi? Pressure gauges are usually one of the first components to go bad. If you needed new seals on the pump or a new motor it would be leaking water, not starting easily, making funny noises, etc. Believe me, you would know BUT it would not be causing the symptoms you are describing!
    If you are starting out at 'normal' pressure, etc and after hours of filtration flow is down and pressure has risen then you need to check your water chemistry (and NOT with strips, they are worthless).
    Also, how have you chemically cleaned the grids? I assume you broke the filter down and totally removed all DE that might have been bridging the grids and then soaked the grids overnight in a degreaser such as REAL TSP (not a substitute ) or automatic dishwasher detergent BEFORE acid washng for abut 4 hours to overnight?
    Acid washing the grids before degreasing them can cause the fast pressure rise you describe since it will clog the grids, often to the point where they need to be replaced!

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    Re: Max pressure 20PSI? cmon!!

    Quote Originally Posted by mas985
    Quote Originally Posted by rentalwhitehemi
    But don't tell me that a max pressure of 20 PSI when I have 0 gpm is irrelevant.
    Assuming you actually have 0 GPM, the maximum head of the pump is then 46'. However, maximum head for a 1HP Superflo is about 65' (28 PSI) so either something is wrong with the pump or flow rate is higher than 0 GPM.
    Or the pressure gauge has gone bad...that would be my first guess since they do fail quite often!
    Also, if the filter PSI rises in a very short period of time, it is either a filter problem or you have something in the water that is getting filtered out (algae). Are you sure your not fighting an algae bloom? Check your cc.
    Or you have clogged grids from impoper cleaning!

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    Re: Max pressure 20PSI? cmon!!

    Thank you to all. These are the kind of responses that I was looking for. I have a few things to look at that I haven't done yet. I was just starting to think that I was going crazy on this one. So if I came off with an attitude that is why. Thanks again.

    One of the things that I have done already is replace the gauge and the readings are the same.

    When I get to the bottom of this I'll post.
    rgil
    15000gal. IG/attached hot tub
    quartz plaster
    Pentair DE filter
    2HP whisperflo pump

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    Re: Max pressure 20PSI? cmon!!

    Quote Originally Posted by rentalwhitehemi
    Thank you to all. These are the kind of responses that I was looking for. I have a few things to look at that I haven't done yet. I was just starting to think that I was going crazy on this one. So if I came off with an attitude that is why. Thanks again.

    One of the things that I have done already is replace the gauge and the readings are the same.

    When I get to the bottom of this I'll post.
    Two things I would look into are ruined grids (because of acid washing before degreasing or because of use of a commercial acid filter cleaner) and water balance issues (suspect nascent algae bloom). Posting a full set of test results, including an overnight FC loss test would be telling (but you cannot do this with strips!)

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