# water pump design **URL:** \ **Category:** Factual Questions\ **Created:** [April 28, 2020, 4:17pm UTC](https://boards.straightdope.com/t/water-pump-design/852745 "2020-04-28T16:17:22Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![PennyNichols](https://avatars.discourse-cdn.com/v4/letter/p/ac91a4/32.png) [@PennyNichols](https://boards.straightdope.com/u/PennyNichols)\ **Post date:** [April 28, 2020, 4:17pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/1 "2020-04-28T16:17:22Z")
Hi, long time lurker, first time poster. Am curious as to the design of these two pumps, am hoping that someone here can answer and explain. This peripheral pump has intake centered to the impeller vortex. > **[Pumps with peripheral impeller PK | Pedrollo Spa](https://www.pedrollo.com/en/pk-pumps-with-peripheral-impeller/125)** > > Sono consigliate per pompare acqua pulita senza particelle abrasive e liquidi chimicamente non aggressivi per i materiali costituenti la pompa.\
> Per la loro affidabilità, semplicità d'uso ed economicità, sono adatte per... This one uses a different design. What is the difference between the two when it comes to the workings and longevity of the pumps? > **[Pumps with peripheral impeller PQ | Pedrollo Spa](https://www.pedrollo.com/en/pq-pumps-with-peripheral-impeller/127)** > > Sono consigliate per pompare acqua pulita senza particelle abrasive e liquidi chimicamente non aggressivi per i materiali costituenti la pompa.\
> Per la loro affidabilità, semplicità d'uso ed economicità, sono adatte per... ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 28, 2020, 4:28pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/2 "2020-04-28T16:28:05Z")
Reported. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 28, 2020, 4:33pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/3 "2020-04-28T16:33:19Z")
It looks like basically the same pump internals and performance, the different appears to be the location of the water inlet. It looks one would chose depending on where one wants the inlet. ---
**Author:** ![PennyNichols](https://avatars.discourse-cdn.com/v4/letter/p/ac91a4/32.png) [@PennyNichols](https://boards.straightdope.com/u/PennyNichols)\ **Post date:** [April 28, 2020, 4:36pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/4 "2020-04-28T16:36:01Z")
This is not spam. Am not trying to advertise this brand of pumps or any other. I am asking because I need to decide what type of pump to buy. If I could find a pic that did not also contain the brand I would use that. So please forget about the brand of pump, this is not an ad. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 28, 2020, 4:36pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/5 "2020-04-28T16:36:18Z")
Isn’t this the kind of detail you would ask the manufacturer of those pumps? The pages you linked to don’t get into the intake specifications, and the intake is the only apparent difference. The PK states usage as “domestic”, while the PQ states usage as “domestic, industrial”. ---
**Author:** ![PennyNichols](https://avatars.discourse-cdn.com/v4/letter/p/ac91a4/32.png) [@PennyNichols](https://boards.straightdope.com/u/PennyNichols)\ **Post date:** [April 28, 2020, 4:41pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/6 "2020-04-28T16:41:42Z")
I wrote the company about this last week, got no reply. Btw, it is an Italian brand, and they might not be able to respond because of personnel problems due to the virus. ---
**Author:** ![PennyNichols](https://avatars.discourse-cdn.com/v4/letter/p/ac91a4/32.png) [@PennyNichols](https://boards.straightdope.com/u/PennyNichols)\ **Post date:** [April 28, 2020, 4:45pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/7 "2020-04-28T16:45:27Z")
> [@TriPolar](#): > > Isn’t this the kind of detail you would ask the manufacturer of those pumps? The pages you linked to don’t get into the intake specifications, and the intake is the only apparent difference. > > The PK states usage as “domestic”, while the PQ states usage as “domestic, industrial”. The intake and output of both pumps is 1 inch. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 28, 2020, 4:56pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/8 "2020-04-28T16:56:02Z")
> [@PennyNichols](#): > > The intake and output of both pumps is 1 inch. The intake location is different as pointed out before. That should be the main consideration in your use. Based on the pictures it seems the PQ has a side intake, at right angles to the impeller shaft. The impeller might not be the same for the PK that has an axial intake since that has to change the direction of the input. All of that will be very specific to this product. What is your application? ---
**Author:** ![Rocketeer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rocketeer/32/4437_2.png) [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)\ **Post date:** [April 28, 2020, 5:46pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/9 "2020-04-28T17:46:19Z")
The second type would have a bit more pressure loss in the inlet, which would negatively affect its performance when the inlet pressure is low. However, inlet pressure is also affected by the plumbing leading to the inlet, especially bends, and by the time you got the central-inlet one plumbed in, it’s very possible that you would have negated any advantages it had. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [April 28, 2020, 5:46pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/10 "2020-04-28T17:46:55Z")
I myself am curious about the application. In my career I specified hundreds, possibly thousands of pumps, and never once a peripheral. Almost exclusively centrifugal, with an occasional progressive cavity, gear, or peristaltic. What’s a peripheral pump used for? ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [April 28, 2020, 10:21pm UTC](https://boards.straightdope.com/t/water-pump-design/852745/11 "2020-04-28T22:21:04Z")
The main difference between the two pumps is going to be the NPSH (Net Positive Suction Head) requirement. In simple words, which pump can “suck” more. The one with the side inlet will be able to “suck” more than the one with the center inlet. You can deduce the same from looking at the specifications: The PQ pump (side inlet) has a maximum fluid temperature spec of 90 degrees C. The PK pump (center inlet) has a max fluid temperature of 60 degrees C. Since the inlet temperature affects the vapor pressure, you can deduce that the center inlet pump will “suck” less. So, if you were installing the pump to pump out water from a deep well, I would go with the PQ pump. These pumps are also used for solar water heater or industrial heater water application which requires higher temp operation / lower NPSH and the PQ pump fits the bill. These pumps can generate very high pressure if they are deadheaded (i.e. the outlet is closed or you go to low flows), so please use appropriate safety relief device. Aas to your question: “What is the difference between the two when it comes to the workings and longevity of the pumps?” - It depends on the application. State what you are using it for and we can reply. The side entry pump will be more tolerant of two-phase flow (bubbles in the liquid). But really I need to see the setup (liquid being pumped, temperatures, suction side design, discharge side , etc. ) to comment on this. If the liquid is fairly cold and its an application with no special suction requirements, I will go with the cheaper of the two, which I think will be the center inlet one. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [April 29, 2020, 12:53am UTC](https://boards.straightdope.com/t/water-pump-design/852745/12 "2020-04-29T00:53:33Z")
> [@am77494](#): > > So, if you were installing the pump to pump out water from a deep well, I would go with the PQ pump. But the specification also says: > [@](#): > > Manometric suction lift up to 8 m …for both pumps. Which I take to mean both can pump from 8m, one up to 60c and the other up to 90c ? ---
**Author:** ![ThisSpaceForRent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thisspaceforrent/32/345_2.png) [@ThisSpaceForRent](https://boards.straightdope.com/u/ThisSpaceForRent)\ **Post date:** [April 29, 2020, 1:14am UTC](https://boards.straightdope.com/t/water-pump-design/852745/13 "2020-04-29T01:14:25Z")
> [@PennyNichols](#): > > This is not spam. Am not trying to advertise this brand of pumps or any other. I am asking because I need to decide what type of pump to buy. If I could find a pic that did not also contain the brand I would use that. So please forget about the brand of pump, this is not an ad. PennyNichols… I know jack shit about pumps, but I know about manners. I assure you the majority of the posters in this thread do not think you are spamming. Welcome to the Straight Dope Message Board. I hope you know your input is valuable and your opinions will be respected. I bet you have a wealth of information and experience to share with this community. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [April 29, 2020, 1:19am UTC](https://boards.straightdope.com/t/water-pump-design/852745/14 "2020-04-29T01:19:07Z")
> [@Melbourne](#): > > Which I take to mean both can pump from 8m, one up to 60c and the other up to 90c ? Yes you are correct but that is at standard conditions I.e. a particular temperature of water which is around 70 F or 25 C or a temperature like that depending on their standards or code. As the temperature goes up, the vapor pressure of water increases and consequently you’ll have to reduce the suction height. (Think of it like this. Say you have water under a given vacuum and it isn’t boiling but if you raise the temperature it will start boiling under the same vacuum) If you want more technical details, since this is a positive displacement pump you can read up on “acceleration head” to distinguish the two designs. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [April 29, 2020, 1:28am UTC](https://boards.straightdope.com/t/water-pump-design/852745/15 "2020-04-29T01:28:58Z")
It is very common in the rotating equipment industry (pumps, compressors, turbines) to use terms that will look like “gotcha” terms to the outsider. For example a 100MW gas turbine will make 100MW only at sea level at standard temperature. Take it any other place higher or hotter and it will be de-rated.