selecting a pump for custom hot tub

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Old 05-01-05, 08:48 AM
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selecting a pump for custom hot tub

hey guys, this summer i'll be building my own hot tub, with a wooden frame. it will be 6'x6', not sure yet of the depth/heighth, but just envision a typical 6x6 commercial spa, 400gallons or less probably...

my plan is to keep the overall cost down, thus justifying the idea of making the hot tub myself -- otherwise i would just shell out 7000 bucks and be done with it. i am studying mechanical engineering right now at nc state, and when I have a plan or project in my head, i tend not to back down from it, i think stuff like this is very entertaining. well, enough of the history here, on with the topic...


given the dimensions of the tub, and given the fact that i will probably only want to buy about 6 water jets (nothing extreme here), what do you think will be the most cost efficient, and yet functional (read: enough jet power and fairly responsive heating time) situation for a pump(s)?

if the jets are powered by water, would it make sense to buy a fairly weak pump to only power the jets, while having a stronger, but still cheap, pump serve only for circulation? or do most hot tubs use the jets as circulation as well? I am kinda confused as to what happens on teh commercial tubs when the user switches off the jets... does water still come out from them? or is there a secondary inlet for the water to come in?

sorry if these questions are basic, and i understand that the pump is the heart of the hot tub, and it will most likely be the most expensive single part that i buy. however, i see some 1hp pumps priced pretty high when you compare to weaker pumps, which could possibly be used in parallel in order for one to power the jets and one to only deal with circulation. the circulation pump will most certainly be a two-speed, i think...

any help is appreciated..
 
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Old 05-01-05, 04:53 PM
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Originally Posted by drone007
hey guys, this summer i'll be building my own hot tub, with a wooden frame. it will be 6'x6', not sure yet of the depth/heighth, but just envision a typical 6x6 commercial spa, 400gallons or less probably...

my plan is to keep the overall cost down, thus justifying the idea of making the hot tub myself -- otherwise i would just shell out 7000 bucks and be done with it. i am studying mechanical engineering right now at nc state, and when I have a plan or project in my head, i tend not to back down from it, i think stuff like this is very entertaining. well, enough of the history here, on with the topic...


given the dimensions of the tub, and given the fact that i will probably only want to buy about 6 water jets (nothing extreme here), what do you think will be the most cost efficient, and yet functional (read: enough jet power and fairly responsive heating time) situation for a pump(s)?

if the jets are powered by water, would it make sense to buy a fairly weak pump to only power the jets, while having a stronger, but still cheap, pump serve only for circulation? or do most hot tubs use the jets as circulation as well? I am kinda confused as to what happens on teh commercial tubs when the user switches off the jets... does water still come out from them? or is there a secondary inlet for the water to come in?

sorry if these questions are basic, and i understand that the pump is the heart of the hot tub, and it will most likely be the most expensive single part that i buy. however, i see some 1hp pumps priced pretty high when you compare to weaker pumps, which could possibly be used in parallel in order for one to power the jets and one to only deal with circulation. the circulation pump will most certainly be a two-speed, i think...

any help is appreciated..
Most use two pumps, one low volume pump for filtering/heating, and a second MUCH larger pump for the jets. More jets you have, larger pump you need.

My *bathtub* has a 2hp pump. A 1hp would be seriously underpowered IMO.

As for heating, the heating functions are always on (via thermostat) when the circulatory pump is running.
 
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Old 05-02-05, 05:38 AM
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interesting that your bathtub uses a 2hp pump... some of the hottub sites have said that they recommend 1hp for every 6 jets or something.

you think it would be possible to design the whole frame and the jet locations first, and then when everything looks nice, I can swap in my first choices of pumps and test it out?.. if they were too weak or too strong, then i could send them back and revise my selection?
 
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Old 05-02-05, 05:51 AM
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Not only is it a 2hp, the jets are actually a little on the weak side (which is fine with me, but most people would prefer it otherwise).

Why not go look at some spas/hot tubs.. see what size pump they use, the number of jets, their size and the piping used to connect them and feel what the jets are like. Any decent retailer is going to have a half dozen or more models up and running.

I guess you could terminate your lines in flexhose with unions, that would let you swap pumps around.
 
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Old 05-02-05, 05:02 PM
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yeh i will prob stop by a few stores when i get off of school for summer... i assume their pumps that control the jets will only be 1-speed, but maybe with a variable valve or something to make the jets stronger or weaker? or maybe not... haha, i had never payed attention to hot tubs back before I wanted to build my own.
 
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Old 05-02-05, 05:21 PM
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hi drone, keep plumbing to 2" where possible on suction / return , hot tub can be plumbed with 11/2" flex 6 jets,

use 1 1 . 5 hp 2 speed purex / pentair whisperflow pump super dependable, performer will drive those jets fine, unless you plan on moving the equipment 75 feet from the spa, if so go to a 2.0 hp whisperflow 2 speed up-grade the plumbing to 21/2 " suction and 2 " on the return.


steve
 
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Old 05-03-05, 08:53 PM
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lol steve... thanks for letting me know what to do if i plan to operate from 75 ft away.


have any idea what i'm paying for with the purex/pentair pumps? i seem to see them listed for 375+... how do they compare to something like this?
http://www.spadepot.com/Merchant2/me...ory_Code=Pumps

i don't really see a company name there
 
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Old 05-04-05, 08:49 AM
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the purex / pentaire whisperflow , is a proven pump, is bulletproof, and pumps more water than any pump normally used in the swimming pool industry, parts are normally in stock at local dealers and most pool / spa techs. are familar with it. don't get crazy trying to save money in this area the " heart of your system "




lol steve
 
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Old 05-05-05, 11:06 AM
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any reason you can see that they're selling the whisperflo for so cheap on this website? all i could see is there is a "1 year warranty" as opposed to the 3 year that all the other sites advertise...

http://www.poolhub.com/Product_files...whisperpro.htm

comparatively, that's a really great price. i could splurge and go for the 2hp one for that type of deal..
 
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Old 05-07-05, 12:56 PM
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in the last yr. almost all manufactures have gone to a 1 year warranty, youll more than likely not need it, especially with the whisperflow. thats all ill install.




steve
 
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