pump for plunge pool

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  #1  
Old 04-29-15, 10:32 AM
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pump for plunge pool

Greetings.

I've made a smallish in-ground plunge pool out of reinforced concrete, conical-shape, 8-feet in diameter and 3' deep. So approximately 500 gallons. I've piped it with 1.25-inch PVC for a drain and a return for a fountain element which I plan to insert when we're not ploshing. This is for a weekend home on a well, so I will not install filtration nor will I have a pump running continuously but merely water the garden (by connecting to the Blue Line irrigation) when we stop using it for the day or weekend.

Silly me... I built the darn thing before discovering that there is an overwhelming number of options for pumps, and they are all frightfully expensive. I am entirely out of my element with these devices.

Can anyone advise a simple, speed-is-not-a-factor, reasonably-priced pump that we can use to drain and to power a fountain? This weekend I will run a dedicated circuit to the pump housing which I will build some 20-feet from the pool.

Thank you in advance for any options or insights you can share.
 
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Old 04-29-15, 12:29 PM
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How much water do you want to move? How much pressure or height do you want from the fountain? Where will the pump be located; above or below the water level of the tank?
 
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Old 04-29-15, 12:57 PM
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Hello Pilot Dane. Thx for your questions.

I'm flexible regarding the amount of water to move. Off the top of my head, let's say I wish to drain the 500 gal pool in one half-hour, meaning we move 250 gph. Now if I can save $100 in pump cost by letting it take an hour to drain, I'd do it.

I don't know beans about pressure, but for height... I'd say 2-3 feet for a spout would be good. I assume I can get attachments to make a nice bell-shaped font or the like; something that looks attractive and sounds calming. If I need to make this decision in order to determine the pump requirements then I would appreciate a reference to fountainheads that I can connect to 1.25" pvc.

I figure to locate the pump some 15-20 feet away from the pool. I assumed it would be above ground but I can easily excavate a foot or two and make a subterranean box on a small concrete pad if that makes a difference in the cost-benefit equation. More than 2-feet and it would become difficult to clean any screens. Two feet deep should keep the pump base below the waterline. If I was just filling up the pool for the fountain only, then I wouldn't necessarilly fill the pool to the brim.

Thank you for giving me the opportunity to learn more parameters and to refine the project.
 
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Old 04-30-15, 05:29 AM
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Your math went the wrong way. To drain a 500 gallon pool in half an hour you need a pump that moves 1'000 gallons per hour. A 500 gallon per hour pump would drain it in an hour.

Most pumps are rated with zero resistance or head. So, in most cases a pump will not produce anywhere near the advertised number. Try to find a head or flow chart for the pump you are considers. It will tell you how much water it can move uphill. In your case three feet. Add in a little extra to account for the resistance of your piping I'd shoot for a pump that moves how much you want at 5 or 6 feet head.

Pumps are a compromise. Pressure and flow rate sorta work opposite each other. For the same horsepower a pump that can generate high pressure/head will have a lower flow rate than a pump designed for lower pressure/head.

Also, since people will be in contact with the water in the pool and the water will be in contact with the pump. It must be on a GFCI protected circuit.
 
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Old 04-30-15, 09:08 AM
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Thanks for catching my bad math and explaining head. I also must add in distance from pool to pump, I believe. (6+20)

So I found a chart for a Hayward SP2600X5. The chart says: Pump Output (GPM) vs. Total Resistance To Flow (Feet of Head) = ~48 which is twice my proposed need (1000/60=17). This means, assuming there are no further errors to my math, that the pool will drain in ~21 minutes. This certainly helps disqualify all HP options greater than 0.5

So the primary difference between a pump placed beneath the level of the waterline or above is the amount of additional head? In other words, placement below waterline increases head?

Am I correct to understand that the only way to have control over a fountainhead pressure is to use a variable speed motor?

Great suggestion about the GFCI. I've had issues in the past with GFCI breakers tripping randomly with long runs and have resorted to using normal breakers and putting in a GFCI receptacle at the wet location. I'd plan to do this at the pump site if no one flags a problem.

Much obliged
 
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Old 04-30-15, 10:06 AM
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The pump you mentioned is much better than what I thought you were considering. I thought you were going for a dinky fountain pump. That's a proper pool pump and will work well.

---

Head is the height from the top of the water in the pool to where it emerges from the pipe and can sometimes include the flow resistance of the pipe and fittings. The elevation of the pump doesn't matter in figuring head.

The elevation of the pump does matter for priming. A non-self priming pump is best installed below the waterline so you don't have to manually prime the pump every time you use it. A self priming pump, even above the waterline will allow you to simply turn it on and soon water will be flowing. Non-self priming pumps are more efficient but that's not a concern with as little as you'll be using the pump. With a self priming pump try to keep the pump as low as possible. At it's maximum 8' self priming height it could take several minutes for it to prime. The closer you get it to the pool's water surface elevation the faster it will prime.

I would shoot to keep it above the water line though. That way if you ever need to work on the pump or clean the basket you can open it up without the pool water gushing out. If you do want to put it below the pool's elevation then I'd put a 1/4 turn ball valve between the pool and pump which you can close to work on the pump when the pool is full.

If you want to vary the flow rate you can restrict the flow on the output side of the pump. Always let the infeed side run free but you can put a valve in the outlet to regulate the flow. I would use a 1/4 turn ball valve since they open fully with almost no restriction to the flow.
 
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Old 04-30-15, 02:09 PM
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"HEAD" is a term used in plumbing to calculate flow rate, or loss of. It's a combination of height the water is moved, and the resistance caused by the plumbing (yes, length adds to head, but it's NOT the measurement of the distance of the pipe, directly...but determined by the length of the pipe, the diameter of the pipe, AND the desired flow rate.). Fitting, such as 90's and T's add significantly to the "head" (for instance, a 1-1/4" 90, is equal in friction loss to 3.8' of straight pipe.)

Basically, you want to look at the flow chart for a particular pump, then subtract the head, or "head loss", to get the actual flow rate you'll achieve in your particular situation.

Put the pump BELOW the surface of the water and you will have FAR fewer problems with it...just put in a couple of cheap valves to turn off for servicing the pump....actually, since you plan on draining it so frequently, forget the valves.
 
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Old 04-30-15, 02:42 PM
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You folks are very lucid. Thank you.

Actually, I was hoping someone might point out a less expensive alternative to this Hayward pump but throwing in a pair of ells and valves and what-not starts edging me up to the max rating anyway. I'll install the ball valves because it is cleaner/safer that way.

Glad to have the alternative to a variable speed pump!

Could I later add a heater to the system for possible midnight plunges?
 
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Old 04-30-15, 04:31 PM
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If a heater may be in the future you'll want a way to add that water to the pool without spraying it through the air which will rapidly cool it. But, if you're going to go to the expense of heating the water why would you dump it frequently? Filtration??? Before you're done you'll have a full blown spa/hot tub.
 
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Old 04-30-15, 05:18 PM
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How should I configure spa filtration? Knowing this, I might make a pad & housing for the pump which will allow future growth.

Could one not divert to the fountain element for hot water input?

Will filtration step up the resistance such that I could need 3/4 HP?
 
  #11  
Old 05-01-15, 05:38 AM
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Yes, you could put in a valve. Turn it one way and the flow goes into the pool through a jet in the side of the pool. Turn the valve the other way and it comes out the fountain.

The pump you are considering is a pool pump and can handle filtration. You would install the filter system on the downstream side of the pump. It will hurt the flow rate some but that's what it's designed to do. You might even consider getting a spa pack which has a pump, heater and controls together in one ready to use package.
 
  #12  
Old 05-02-15, 09:25 AM
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Brilliant idea, but I already ordered the SP2600X5. Will the likes of the Apollo 11 Digital Spa Controller /Spa Pack or United's CR Controller work in tandem with the Hayward pump? Or return the Hayward and pickup one of these packs and a filter?

It'll probably cost an arm and a leg to heat an in-ground pool electrically, no?
 
  #13  
Old 05-03-15, 06:09 AM
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I think the pump you ordered is a single speed so it is either on or off. The controller you mentioned is for a two speed pump.

For a heater system to work water has to be flowing. Systems with a heater generally run the pump at low speed continuously or there is a separate circulation pump that runs continuously. This provides continuous filtration and keeps a steady stream of water flowing by the thermostat so it can sense the spa's temperature. The controller then knows when to turn the heater on and off and the continuous water circulation means there is water flowing through the heater. High speed on the main pump is only used when you "hit the jets".

So, look for controllers designed to work with a single speed pump and a circulation pump. This is how Hot Spring spa's operate.

If your plunge pool is not insulated then yes, heating it will be expensive. How expensive would depend on how hot you want it and how long you heat it. If you keep it continuously at 100f it would be more than simply "taking the edge off" especially if you only do it occasionally.
 
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Old 05-04-15, 04:14 PM
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> ...simply "taking the edge off" especially if you only do it occasionally.

Wow. Perfect for helping to make the plunge easier for tentative toes.

Can you recommend a simple heater (or minimum criteria) for the SP2600X5 with 1.25-inch lines?




> Put the pump BELOW the surface of the water and you will have FAR fewer problems with it..

Decided against this cause of potential pooling in winter storms. Waterproofing below ground locations has always been time-consuming or inadequate for me.


Thanks again for all the experience-based orientation here.
 
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Old 05-04-15, 04:39 PM
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Heating ?!?!?!..... electric

You've got the highest electric rates in the nation. I don't think you'd want a straight electric heater. The buy price is low but it requires large power wires and is expensive to run.

The most bang for the buck is gas followed by a heat pump. A heat pump runs just on electric. Doesn't require massive wiring. Is fairly efficient but the up front cost is high.

Here's a good site for explaining the differences.....
What is the Best Type of Heater for a Swimming Pool/Spa ? - Aqua Cal
 
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Old 05-05-15, 06:17 AM
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You have all sorts of options. Most professional would be choosing a spa heater. 1.5kw brings my 300 gallon spa up about 1 to 1.5f per hour but there are formulas you can use to calculate how many electrons you need to burn to raise the temp of your water. No matter what you do it will be a balance between cost and water temp. Heating 500 gallons will take a fair bit of energy and what makes it worse is that you plan to dump the water so all that energy is wasted.
 
  #17  
Old 05-05-15, 07:36 AM
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A 1.5kW electric heater would NEVER even begin to heat an UNINSULATED INGROUND 500 gallon body of water.
 
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Old 05-05-15, 07:52 AM
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Okay, it does not look like heating is an immediately practicable solution for my uninsulated pool. The natural gas line is faaar away and I choke just reading about the costs of those various heaters and pumps on the Aqua Cal page.

I have in the past seen passive solar solutions, though for baths not pools. They look like a large box of clear flourescent tubes in a black ground/frame which sits on the roof of many houses abroad. And, come to think of it, I have an old 300-gallon expansion tank sitting around unused. Perhaps if I examine one of those solar devices more closely then I can rig up a comparable unit.

Aha, I just found an example:
ProgressivTube Passive Solar Water Heaters | San Jose California | Gull Solar

and DIY instructions:
How to Build a Passive Solar Water Heater - Green Homes - MOTHER EARTH NEWS


The SP2600X5 arrived yesterday and looks beefy enough to launch a manned module. That will be my perk with this new plunge pool: using the chemical-free water at the touch of a button to irrigate a garden without having to bail out a mucky mess as was the case with the old cracked pool this one replaces. The fountain will be another perk.
 
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Old 05-05-15, 11:00 AM
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A "passive" heater would need to be installed BELOW the water level of your spa. Up on the roof, above the water, it becomes non-passive, "active", and would need to have the pump, pump water through it..as well as a controller to control when the pump runs.
 
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Old 05-05-15, 12:29 PM
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How long will you be leaving your pool filled? How long will you fill it before using it? Solar is great but it's not fast and you need to have a collector big and efficient enough to collect enough heat in 6 peak hours to overcome morning, evening and night when it won't be heating. If it takes it a week to get the pool up to the temp you want the water may start getting funky before it's even ready to be used.
 
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