How much PSI can this pump produce?

Discussion in 'Home Repair' started by Stuart Benoff, Aug 23, 2006.

  1. I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    #173840-20 attached to my pool to run a pool cleaner. I don't have the
    official specs for it so would anyone know how to calculate how much PSI
    this pump can/should produce?

    Thank you.
     
    Stuart Benoff, Aug 23, 2006
    #1
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  2. "Stuart Benoff" <> wrote in message
    news:echg99$cgiq$...
    >I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    >#173840-20 attached to my pool to run a pool cleaner. I don't have the
    >official specs for it so would anyone know how to calculate how much PSI
    >this pump can/should produce?
    >
    > Thank you.


    I think most pumps are rated Gallons per minute GPM. pool system run at
    a very low PSI 10 to 20.
     
    Sacramento Dave, Aug 23, 2006
    #2
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  3. Sacramento Dave wrote:
    > "Stuart Benoff" <> wrote in message
    > news:echg99$cgiq$...
    >
    >>I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    >>#173840-20 attached to my pool to run a pool cleaner. I don't have the
    >>official specs for it so would anyone know how to calculate how much PSI
    >>this pump can/should produce?
    >>
    >>Thank you.

    >
    >
    > I think most pumps are rated Gallons per minute GPM. pool system run at
    > a very low PSI 10 to 20.
    >
    >


    That's interesting because the cleaner that it's attached to says that
    it needs between 20 and 25 PSI for it to be completely effective. You'd
    think that they would say between X and Y GPM?
     
    Stuart Benoff, Aug 23, 2006
    #3
  4. "Stuart Benoff" <> wrote in message
    news:echg99$cgiq$...
    >I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    >#173840-20 attached to my pool to run a pool cleaner. I don't have the
    >official specs for it so would anyone know how to calculate how much PSI
    >this pump can/should produce?
    >
    > Thank you.


    Pressure gauge in the line
     
    Edwin Pawlowski, Aug 23, 2006
    #4
  5. Stuart Benoff

    Chris Lewis Guest

    According to Stuart Benoff <>:
    > Sacramento Dave wrote:
    > > "Stuart Benoff" <> wrote in message
    > > news:echg99$cgiq$...
    > >
    > >>I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    > >>#173840-20 attached to my pool to run a pool cleaner. I don't have the
    > >>official specs for it so would anyone know how to calculate how much PSI
    > >>this pump can/should produce?
    > >>
    > >>Thank you.

    > >
    > >
    > > I think most pumps are rated Gallons per minute GPM. pool system run at
    > > a very low PSI 10 to 20.


    > That's interesting because the cleaner that it's attached to says that
    > it needs between 20 and 25 PSI for it to be completely effective. You'd
    > think that they would say between X and Y GPM?


    Flow rate is dependent on PSI, so they pick the one that's of most
    importance to the device to spec it. This device cares more about
    pressure than flow rate.

    With a freshly cleaned sand filter, my pool pump produces about
    15PSI on the manifold's pressure guage. As the sand filter
    gunks up, the pressure rises.

    My pump will produce about 35PSI if the outlet is completely plugged.

    [We've tee'd the discharge system into a fire hose. If you shut
    the fire hose's nozzle off, pump pressure hits 35PSI.]
    --
    Chris Lewis, Una confibula non set est
    It's not just anyone who gets a Starship Cruiser class named after them.
     
    Chris Lewis, Aug 23, 2006
    #5
  6. Chris Lewis wrote:
    > According to Stuart Benoff <>:
    >
    >>Sacramento Dave wrote:
    >>
    >>>"Stuart Benoff" <> wrote in message
    >>>news:echg99$cgiq$...
    >>>
    >>>
    >>>>I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    >>>>#173840-20 attached to my pool to run a pool cleaner. I don't have the
    >>>>official specs for it so would anyone know how to calculate how much PSI
    >>>>this pump can/should produce?
    >>>>
    >>>>Thank you.
    >>>
    >>>
    >>> I think most pumps are rated Gallons per minute GPM. pool system run at
    >>>a very low PSI 10 to 20.

    >
    >
    >
    >>That's interesting because the cleaner that it's attached to says that
    >>it needs between 20 and 25 PSI for it to be completely effective. You'd
    >>think that they would say between X and Y GPM?

    >
    >
    > Flow rate is dependent on PSI, so they pick the one that's of most
    > importance to the device to spec it. This device cares more about
    > pressure than flow rate.
    >
    > With a freshly cleaned sand filter, my pool pump produces about
    > 15PSI on the manifold's pressure guage. As the sand filter
    > gunks up, the pressure rises.
    >
    > My pump will produce about 35PSI if the outlet is completely plugged.
    >
    > [We've tee'd the discharge system into a fire hose. If you shut
    > the fire hose's nozzle off, pump pressure hits 35PSI.]


    I'm trying to determine if there is a problem with the pump. When I put
    a pressure gauge on the line it reads 14-15 PSI however, this is a
    'booster' pump not the mail pool pump. It's designed to send
    pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
    and recommended a pump of this size. So, I'm trying to determine if the
    pump is undersized or whether or not there's a problem with the pump.
     
    Stuart Benoff, Aug 23, 2006
    #6
  7. Stuart Benoff

    Chris Lewis Guest

    According to Stuart Benoff <>:

    > I'm trying to determine if there is a problem with the pump. When I put
    > a pressure gauge on the line it reads 14-15 PSI however, this is a
    > 'booster' pump not the mail pool pump. It's designed to send
    > pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
    > and recommended a pump of this size. So, I'm trying to determine if the
    > pump is undersized or whether or not there's a problem with the pump.


    The question is whether the booster pump reads 14-15 PSI _with_ the
    pool cleaner attached. Does it? Or are you measuring the pressure
    without the pool cleaner attached with the pump discharging some other
    way? Are you measuring the pressure at the pump or at the cleaner?
    Try attaching the cleaner and _then_ see what the PSI is at _both_
    the pump and cleaner ends.

    [I'm not familiar with the use of pool cleaners working on the
    pressure side of the pump. It _may_ also be that your plumbing is
    undersized or restricted. In which case, the PSI at the pump
    end will be okay, but at the cleaner end it won't be.]

    Think of it this way - a device like the pool cleaner needs to be
    specified at a specific pressure AND flow rate. Eg: "to operate
    properly, this device needs 1GPM or more at a pressure of 15PSI
    or more".

    Secondly, the plumbing between the two devices matter - it has
    to be large enough to permit the GPMs that the cleaner needs
    without excessive PSI loss.

    Industrial equipment is rated/matched that way. So are, for example,
    tools for use with air compressors (eg: "this tool consumes
    x CFM at y PSI").

    The PSI of the output of a pump varies inversely with the GPM
    the outlet is permitting.

    Pumps _tend_ to have a given "PSI vs GPM" curve given the
    HP rating of the pump. In the middle "design range" (of GPMs),
    it's pretty much determined by the HP of the pump.

    It's not linear, but at least for the most part, two pumps with
    the same HP rating _should_ push just about the same amount of GPMs
    at the same PSI as each other.

    So, if it's the right HP, it (probably) _should_ work.

    But, without knowing the GPM requirements of the cleaner or the expected
    GPM vs PSI curve of the pump, it's difficult to be absolutely certain
    whether a given combination _should_ work or not, and the best bet is
    probably to call the manufacturer (cleaner manufacturer _first_),
    explain your situation mentioning model numbers etc, and they should be
    able to tell you whether the cleaner or the pump are working in spec or not.

    The cleaner manufacturer is probably intimately familiar with the
    behaviour of the cleaner with every pump on the market. If they
    tell you "we have lots of cleaner customers using that pump
    satisfactorily", you _know_ that something's wrong with one
    (or both) of the devices. They may tell you that there's
    something specifically "odd" about that pump that means it won't
    work. Or they may tell you that the plumbing is too small.
    --
    Chris Lewis, Una confibula non set est
    It's not just anyone who gets a Starship Cruiser class named after them.
     
    Chris Lewis, Aug 23, 2006
    #7
  8. Chris Lewis wrote:
    > According to Stuart Benoff <>:
    >
    >
    >>I'm trying to determine if there is a problem with the pump. When I put
    >>a pressure gauge on the line it reads 14-15 PSI however, this is a
    >>'booster' pump not the mail pool pump. It's designed to send
    >>pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
    >>and recommended a pump of this size. So, I'm trying to determine if the
    >>pump is undersized or whether or not there's a problem with the pump.

    >
    >
    > The question is whether the booster pump reads 14-15 PSI _with_ the
    > pool cleaner attached. Does it? Or are you measuring the pressure
    > without the pool cleaner attached with the pump discharging some other
    > way? Are you measuring the pressure at the pump or at the cleaner?
    > Try attaching the cleaner and _then_ see what the PSI is at _both_
    > the pump and cleaner ends.
    >
    > [I'm not familiar with the use of pool cleaners working on the
    > pressure side of the pump. It _may_ also be that your plumbing is
    > undersized or restricted. In which case, the PSI at the pump
    > end will be okay, but at the cleaner end it won't be.]
    >
    > Think of it this way - a device like the pool cleaner needs to be
    > specified at a specific pressure AND flow rate. Eg: "to operate
    > properly, this device needs 1GPM or more at a pressure of 15PSI
    > or more".
    >
    > Secondly, the plumbing between the two devices matter - it has
    > to be large enough to permit the GPMs that the cleaner needs
    > without excessive PSI loss.
    >
    > Industrial equipment is rated/matched that way. So are, for example,
    > tools for use with air compressors (eg: "this tool consumes
    > x CFM at y PSI").
    >
    > The PSI of the output of a pump varies inversely with the GPM
    > the outlet is permitting.
    >
    > Pumps _tend_ to have a given "PSI vs GPM" curve given the
    > HP rating of the pump. In the middle "design range" (of GPMs),
    > it's pretty much determined by the HP of the pump.
    >
    > It's not linear, but at least for the most part, two pumps with
    > the same HP rating _should_ push just about the same amount of GPMs
    > at the same PSI as each other.
    >
    > So, if it's the right HP, it (probably) _should_ work.
    >
    > But, without knowing the GPM requirements of the cleaner or the expected
    > GPM vs PSI curve of the pump, it's difficult to be absolutely certain
    > whether a given combination _should_ work or not, and the best bet is
    > probably to call the manufacturer (cleaner manufacturer _first_),
    > explain your situation mentioning model numbers etc, and they should be
    > able to tell you whether the cleaner or the pump are working in spec or not.
    >
    > The cleaner manufacturer is probably intimately familiar with the
    > behaviour of the cleaner with every pump on the market. If they
    > tell you "we have lots of cleaner customers using that pump
    > satisfactorily", you _know_ that something's wrong with one
    > (or both) of the devices. They may tell you that there's
    > something specifically "odd" about that pump that means it won't
    > work. Or they may tell you that the plumbing is too small.


    The pump is sending water to the wall outlet and then the cleaner is
    attached to the wall. The 14-15 PSI reading is from the wall outlet
    without the cleaner attached. When I take the measurement from the end
    of the hose that attaches to the cleaner it's at 11 PSI. The hose is a
    5/8" hose and is about 22 feet long.

    The pump is a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    #173840-20 but I can't find the specs for it online.

    I also did as you suggested and called the manufacturer of the cleaner.
    Their 3/4 hp pump is capable of 67-80 GPM but they couldn't help with
    the specs for my Magnetek pump and didn't have any info stating that
    this pump wouldn't work with their cleaner. I'm still looking for a
    phone number for Magnetek. Their website refers people to AO Smith
    (http://www.aosmithmotors.com/html/contactUs.html) so I wrote to them
    because they don't have a published phone number.

    Thank you.
     
    Stuart Benoff, Aug 23, 2006
    #8
  9. Stuart Benoff

    Bob Guest

    "Stuart Benoff" <> wrote in message news:echv51
    > The pump is sending water to the wall outlet and then the cleaner is
    > attached to the wall. The 14-15 PSI reading is from the wall outlet
    > without the cleaner attached. When I take the measurement from the end
    > of the hose that attaches to the cleaner it's at 11 PSI. The hose is a
    > 5/8" hose and is about 22 feet long.


    All these measurments are going to vary with the water flow. You need
    to measure with the cleaner attached and operating, with no leakage which
    will lower the reading. Where the booster pump gets its water will affect
    the reading. If it connects to the water return line to the pool, it will start
    with low pressure. If it connects to the outlet of the pump, before the
    filter, it will start with higher pressure and end up with a higher boosted
    pressure.

    Bob
     
    Bob, Aug 23, 2006
    #9
  10. Stuart Benoff

    Chris Lewis Guest

    According to Stuart Benoff <>:

    > The pump is sending water to the wall outlet and then the cleaner is
    > attached to the wall. The 14-15 PSI reading is from the wall outlet
    > without the cleaner attached.


    Is the wall outlet free flowing or plugged?

    > When I take the measurement from the end
    > of the hose that attaches to the cleaner it's at 11 PSI.


    Same question.

    > The hose is a 5/8" hose and is about 22 feet long.


    I think you need to connect the cleaner to the line and then
    measure pressure, at both ends. The drop from 14-15 to 11
    seems a bit high, suggesting the hose is undersized.

    5/8" garden hose? Use 3/4" high quality hose. Some 5/8"
    hoses are quite flow restricted, especially those with cheap
    end fittings. This could be your problem right there.

    > The pump is a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    > #173840-20 but I can't find the specs for it online.


    3/4HP Magneteks appears to be one of the pumps of choice for pool
    cleaners according to the number of hits on Google. Eg: they're
    bundled with Polaris and other units.

    So it should be working with yours.

    > I also did as you suggested and called the manufacturer of the cleaner.
    > Their 3/4 hp pump is capable of 67-80 GPM


    67-80GPM at 20PSI? Good grief, that's _high_ for a 3/4HP unit. I'd
    expect a pump delivering that performance to be 2HP or more.

    You simply _cannot_ push 67 GPM thru even 3/4" copper pipe with any
    sort of efficiency, the friction losses are _enormous_[+]. 13 GPM is
    more like an acceptable upper limit thru pipe that size. 1/2" pipe
    is around 8 GPM max, and garden hose (smaller "real" diameter compared
    to nominal inside diameter) will be less. Especially since
    some cheap garden hose has very restrictive hose fittings. Watch
    out for restrictive valves too (if there are any valves in the line).
    Use full aperture ball or gate valves. Washer type stop valves
    are quite flow restrictive.

    Are you sure they didn't say 6.7-8.0 GPM? _That_ is reasonable,
    and suggests that the hose (if you supplied it) is likely at fault.

    [+] There is a "practical speed limit" for efficient pushing of
    water through pipe, above it, the friction loss becomes ridiculously
    high. With 3/4" copper/PVC, that "speed limit" is achieved at roughly
    13-15GPM. Trying to exceed 13-15GPM in 3/4" pipe means that you have
    to size the pump FAR larger than necessary (and thus waste a lot
    of money) to get the device to work. If you don't size the pump
    that large, the device simply doesn't get the water volume it needs.
    --
    Chris Lewis, Una confibula non set est
    It's not just anyone who gets a Starship Cruiser class named after them.
     
    Chris Lewis, Aug 23, 2006
    #10
  11. Chris Lewis wrote:
    > According to Stuart Benoff <>:
    >
    >
    >>The pump is sending water to the wall outlet and then the cleaner is
    >>attached to the wall. The 14-15 PSI reading is from the wall outlet
    >>without the cleaner attached.

    >
    >
    > Is the wall outlet free flowing or plugged?


    Free flowing

    >
    >>When I take the measurement from the end
    >>of the hose that attaches to the cleaner it's at 11 PSI.

    >
    >
    > Same question.
    >


    Free Flowing

    >
    >>The hose is a 5/8" hose and is about 22 feet long.

    >
    >
    > I think you need to connect the cleaner to the line and then
    > measure pressure, at both ends. The drop from 14-15 to 11
    > seems a bit high, suggesting the hose is undersized.
    >
    > 5/8" garden hose? Use 3/4" high quality hose. Some 5/8"
    > hoses are quite flow restricted, especially those with cheap
    > end fittings. This could be your problem right there.
    >


    This is a 5/8" rigid high pressure hose kit supplied by Hayward. It has
    several joints to allow the cleaner to reach the corners of the pool
    without getting tangled on it's own hose. It's part number is AX6000HA
    (retail cost is about $180) so this is no garden hose!

    >
    >>The pump is a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
    >>#173840-20 but I can't find the specs for it online.

    >
    >
    > 3/4HP Magneteks appears to be one of the pumps of choice for pool
    > cleaners according to the number of hits on Google. Eg: they're
    > bundled with Polaris and other units.
    >
    > So it should be working with yours.


    Right. I am thinking there's a problem with the pump. I'll open it up
    and check the impeller, etc. It is 6 or 7 years old so maybe it's time
    to replace it?

    >
    >>I also did as you suggested and called the manufacturer of the cleaner.
    >>Their 3/4 hp pump is capable of 67-80 GPM

    >
    >
    > 67-80GPM at 20PSI? Good grief, that's _high_ for a 3/4HP unit. I'd
    > expect a pump delivering that performance to be 2HP or more.
    >
    > You simply _cannot_ push 67 GPM thru even 3/4" copper pipe with any
    > sort of efficiency, the friction losses are _enormous_[+]. 13 GPM is
    > more like an acceptable upper limit thru pipe that size. 1/2" pipe
    > is around 8 GPM max, and garden hose (smaller "real" diameter compared
    > to nominal inside diameter) will be less. Especially since
    > some cheap garden hose has very restrictive hose fittings. Watch
    > out for restrictive valves too (if there are any valves in the line).
    > Use full aperture ball or gate valves. Washer type stop valves
    > are quite flow restrictive.
    >
    > Are you sure they didn't say 6.7-8.0 GPM? _That_ is reasonable,
    > and suggests that the hose (if you supplied it) is likely at fault.


    I thought he said 67 but we had a small language barrier so I suppose he
    could have said 6 to 7 and not 67. Now that I think about it 67 gallons
    of water is a lot to move in 1 minute.

    >
    > [+] There is a "practical speed limit" for efficient pushing of
    > water through pipe, above it, the friction loss becomes ridiculously
    > high. With 3/4" copper/PVC, that "speed limit" is achieved at roughly
    > 13-15GPM. Trying to exceed 13-15GPM in 3/4" pipe means that you have
    > to size the pump FAR larger than necessary (and thus waste a lot
    > of money) to get the device to work. If you don't size the pump
    > that large, the device simply doesn't get the water volume it needs.


    Thank you for your help!
    Stu
     
    Stuart Benoff, Aug 23, 2006
    #11
  12. Stuart Benoff

    Chris Lewis Guest

    According to Stuart Benoff <>:

    [his posting showed that it was the proper "lines" for the
    application.]

    > Right. I am thinking there's a problem with the pump. I'll open it up
    > and check the impeller, etc. It is 6 or 7 years old so maybe it's time
    > to replace it?


    Pumps tend either to work to full (or darn close to full) spec, or not
    at all. Anything "intermediate" to that will probably not be something
    that needs the pump to be replaced (eg: plugged impeller, other
    obstructions), or be very obvious (eg: the pump motor/bearings are _very_
    hot, major housing leakage etc.).

    Depending on how the impeller is designed, it may be partially plugged.
    Or perhaps badly chipped.

    Our pool pump plugs up with debris from a certain plant that sheds
    for a short period during the summer - this stuff is rather like
    short pine needles, gets through all the screens, and promptly
    plugs up the impeller. It's not an "open impeller" (one circular
    plate with vanes), it's more like a water wheel with very small openings
    (two plates with narrow curved water channels between them). Has to be
    disassembled and cleaned out once or twice a year with pipe
    cleaners - you know, the "fuzzy wire" kind ;-). Symptom is simply
    poor flow.

    [Seem to have bypassed _that_ problem this year.]

    Given that pool water is usually relatively well screened before
    it hits the pump, that type of impeller could be fairly normal
    for pool boosters too.

    > I thought he said 67 but we had a small language barrier so I suppose he
    > could have said 6 to 7 and not 67. Now that I think about it 67 gallons
    > of water is a lot to move in 1 minute.


    Yah.
    --
    Chris Lewis, Una confibula non set est
    It's not just anyone who gets a Starship Cruiser class named after them.
     
    Chris Lewis, Aug 23, 2006
    #12
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