# How much PSI can this pump produce?

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

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?
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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.
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Chris Lewis wrote:

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.
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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[s] (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.
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Chris Lewis wrote:

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.
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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
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Is the wall outlet free flowing or plugged?

Same question.

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.

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.

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.
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Chris Lewis wrote:

Free flowing

Free Flowing

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!

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 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.

Thank you for your help! Stu
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[his posting showed that it was the proper "lines" for the application.]

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.

Yah.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Stuart Benoff writes:

Advice in this thread is confusing pool *circulation* pumps with pool cleaner *booster* pumps. They are very different. The booster pump characteristics, the lines and hoses, and other components are not comparable to the usual guidelines for circulation pumps.
Why? The purpose of the booster pump is to create and transmit hydrodynamic power to the cleaner for application in the turbine motor and the venturi vacuum, not so much to move water volume which is adequately delivered as a by-product of the power transfer. This power has to go thru a skinny hose so as to maintain flexibility. So you want a pump that delivers low volume at high pressure. It's the opposite for pool circulation pumps, where you want high volume circulating and absolutely don't care about pressure for pressure's sake. This is analogous to electrical power transmission and why high-voltage lines are used for long distances.
I am not up to date on the exact specs, but I believe your 15 psi is way too low. When my Polaris 180 comes off the hose and the loose hose flails around the pool, the water coming out is like an 80 psi city water faucet.
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Pressure gauge in the line
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