Above Ground Pool Plumbing Size

[Dirk]

This from a Gulf Stream HP owner manual:

Plumbing Sequence
The piping sequence is: pool pump – filter – heater – solar - chlorination system(s) – pool. Rigid PVC piping is recommended and all joints secured with PVC glue. Installation MUST conform to all local codes. Make sure water-flow is correct as indicated on back of heater. Again, try to keep piping away from areas that may be tripped over or stepped on when operating heater or servicing. Try to keep elbows and piping to a minimum to avoid excessive pressure drop. We use a full-flow heat exchanger so no external bypass is needed up to 70 GPM.

Three interesting tidbits. This manual also mentions the need for a bypass, but not unless the flow is above 70GPM. Which would imply 90GPM would be more than this Gulf Stream HP model can handle. Also note the manual indicates the correct flow rate (perhaps optimal flow rate?) is indicated on the back of the heater. And three: "We use a full-flow heat exchanger..." which reads to me like you can throw all the flow you got at it, up to 70GPM.

Here's the reference. I couldn't actually find in this manual to which model the manual belonged:

https://www.gulfstreamheatpump.com/wp-content/uploads/2020/09/HO-Manual-2020-V5.5.pdf

 

[kimkats]

I wanted another return in my pool but hubby said NOPE! as he did NOT want to add holes to it for the very reason you are worried about. Our single skimmer and return seems to work just fine once I used ping pong balls to how how to turn the return eyeball. The cats loved watching the balls going around so it was a win all the way around LOL

 

[JKB121]

Any chance it wasn't GPM? 90 Liters/minute would be 24GPM... Or maybe 90GPM is max allowable?

I found this deep in the manual. Why they have 90 GPM on the cover is an unknown...


"Rigid PVC piping is recommended, and all joints secured with PVC glue. Installation MUST

conform to all local codes. Make sure water-flow is correct (30-70 GPM). Again, try to

keep piping away from areas that may be tripped over or stepped on when operating

heater or servicing. Try to keep elbows and piping to a minimum to avoid flow restrictions.

We use a full-flow heat-exchanger, so no external bypass is needed up to 70 GPM."

 

[JKB121]

You are not going to get anywhere near 90GPM. Most IG pool flow runs 30-50 GPM. Heat pumps run fine with flow slightly above what engages the pressure switch, a bit above 30 GPM.

You want to keep the water velocity below 6 ft/sec on the suction and below 8 ft/sec on the pressure side of the pump. To run at 90GPM you should have 2.5" piping.

Pipe Size6 ft/sec8 ft/sec1.5"38 GPM51 GPM2"63 GPM84 GPM2.590 GPM119 GPM3.0"138 GPM184 GPM
You have a lot in your equipment that will prevent you from running at 90 GPM including your filter. And a single skimmer can't draw water in at 90 gpm.

Give the 2" pipe a try and see what the flowmeter says your GPM is. But your AGP has a lot of inefficiencies in heating that reduce the effectiveness of your HP.

So now that we know we are looking at 70 GPM or even lower, (30 to 70) I could probably live with shooting for 50 GPM. With that said, does it really make sense to up the 1.5" PVC to 2" PVC when I'm still going to be limited by the 1.5" filter connection and the 1.5" return port with the 3/4" eyeball? I could drill out the skimmer and install a 2" bulkhead and get 2" to the pump easy enough. Cutting a hole in for another return is not an option as I'm not looking to void the warranty.

 

[JKB121]

@ajw22 I just read this article you posted. Do Different PVC Fittings Really Make a Difference in Water Flow? - POND Trade Magazine A nice easy read. With all the input to my question, I think I will increase the 1.5" PVC to 2" PVC using long sweeps. I'm just left with one question.... Will the single return with the 3/4" eyeball cause enough restriction to make the effort not worth it? If so, is there a larger eyeball? I've not found any. I might add that occasionally we will find the eyeball floating in the pool when the pump is on high. It is a factory fitting and eyeball. (Doughboy). I guess the pump blows it out.

 

[Dirk]

Here's a 1".

Amazon.com: Waterway Above-Ground Pool Vinyl Liner Deluxe Return Fitting Assembly 1 Inch Eyeball White 550-9340: Garden & Outdoor

Amazon.com: Waterway Above-Ground Pool Vinyl Liner Deluxe Return Fitting Assembly 1 Inch Eyeball White 550-9340: Garden & Outdoor

www.amazon.com

I saw other types of 1" as well. Didn't see anything bigger.

 

[ajw22]

Will the single return with the 3/4" eyeball cause enough restriction to make the effort not worth it? If so, is there a larger eyeball? I've not found any. I might add that occasionally we will find the eyeball floating in the pool when the pump is on high. It is a factory fitting and eyeball. (Doughboy). I guess the pump blows it out.

No.

The eyeball size has an effect on the pressure of the water coming out of the return versus the flow of the water through the pipes.

With a fluid you have the flow in GPM and the pressure that flow creates. Flow and pressure are inversely affected by the pipe size. As you reduce the pipe size with the same flow the pressure will increase.

A smaller eyeball creates a higher pressure plume of water into your pool to help with the circulation and move the water around. That is why spa jets have small holes to give you a high pressure spray. If your return was a big hole water would just dribble out.

Your pump HP has the most effect on the GPM you can push through your plumbing. That is why you have lower GPM with your 2 speed pump on low versus high. A 2.5 HP pump can easily do 50 GPM or more.

Your skimmer and filter much more limit the flow your 2.5 HP pump can do then your pipe size or eyeball. Your pump can only do as much flow as your single skimmer can deliver to it. That is why IG pools that need high flows have 2 skimmers plus maybe a main drain with large pipes feeding a high HP pump. And your profile does not state what filter you have.

I would be surprised if your pump running at high speed is not doing 30+ GPM now with your existing setup. Like I said in the beginning, that engineer may have sounded knowledgeable but he gave you their out of the book answer of their HP was designed for 2" plumbing. That does not mean 1.5" plumbing makes that much of a difference between their HP working or not.

And if you would have asked him what size plumbing is inside their HP you would have learned that the heat exchange coil in the HP is 1" or less piping. So you feed 2" piping into the HP and it goes into a 1" or 3/4" coil and then back out to 2" pipe. Now what happens at those transitions is you get changes in speed and pressure of the water based on Bernoulli's principle. That is the same principle as to why you have a 3/4" eyeball.

How about we get back to what your complaints are with the heating performance of your HP and work on that problem from the beginning instead of the wild goose chase the engineer sent you down?

 

[JKB121]

Sounds good to me!! The filter is a Hayward cartridge filter. 175 square feet of filter area, designed flow rate is 120 GPM.
So back to the original problem. The HP will randomly shut down and report an error code that reveals "low flow", and high heat inside of the exchanger. Keep in mind, the exchanger inside of this HP is 5 coils about 30" circle of 2.25" pipe, (outside diameter) not 3/4" or 1". The only other clue is it has never shut off during the day, but only during the night when it is cooler outside. The Engineer's theory is that it is running longer and building up heat that is not being exchanged to the pool. According to him, this code only triggers after sensing low flow 5 times in a period of time. Additionally, their estimate of cost to heat 18,000 gallons in my Zip Code to 88* between April and October is $500.00. What I'm seeing is $400.00/month instead. Apparently I'm not getting all the heat out of the exchanger into the pool. That's my real problem...

 

[ajw22]

Interesting the coil size Gulfstream uses.

" building up heat that is not being exchanged to the pool " - The HP takes heat from the atmosphere and transfers it to the water. Heat can't build up any place. It is either in the air or in the water. When the HP is low on refrigerant the heat transfer can be poor and inefficient and the HP can electrically run and not transfer much heat to the water.

Has the refrigerant level been checked for proper charge?

The Raypak HP calculator says it can cost you around $1,400 to heat your pool with April and October over $300/month. Not that far off from your $400/month.

And I think that calculator assumes an inground pool. Your AGP has more heat loss from all the walls and piped that are not insulated by being in the ground.

$400/month in which months?

Post the data plates of your HP.

What is your fully loaded electrical cost/kwh?

Heat Pump Heater Sizing

 

[JKB121]

Has the refrigerant level been checked for proper charge?

It has not. It was purchased new and installed last spring. I don't know if it functions like an air conditioner that is low on refrigerant, but it does not freeze up like an AC would do.

$400/month in which months?

April through October. July and August was lower. Probably 200.00 those months. Electricity is .06/KWH

The HP is shrink wrapped for the winter so no access to the plate now. Based on the Raypak calc. maybe I'm not far off on cost. I do know this one has a 6.1 efficiency rating if that helps. I'm not sure where their calculator comes from. If the cost to run is close, then I still have the low flow error to deal with.

 

[ajw22]

It has not. It was purchased new and installed last spring. I don't know if it functions like an air conditioner that is low on refrigerant, but it does not freeze up like an AC would do.

A HP is an AC system in reverse. Your AC system extracts cold from the air so if it is inefficient it freezes up. Your HP extracts heat from the air and will overheat if low on refrigerant. I would have it checked.

The HP is shrink wrapped for the winter so no access to the plate now. Based on the Raypak calc. maybe I'm not far off on cost. I do know this one has a 6.1 efficiency rating if that helps. I'm not sure where their calculator comes from. If the cost to run is close, then I still have the low flow error to deal with.

I want to see the amps on the data plate and calculate how many hours your HP would need to run at your electrical rate to cost $400.

I would install the flow meter and maybe repipe with 2" to humor the engineer. I think the flow meter will show you have plenty of flow unless you have some restriction that is limiting your 2.5 HP pump. Your pump is plenty powerful to get the flow.

 

[JKB121]

Hey Allen, I agree with you on installing his flow meter this spring. Here is some info from the manual. Our electricity is .06/kwh

BrandGulfstream
Heater Type:
Heat Only
Performance
kW Input:
5.5
BTU Output, Standard Rating Conditions 80/80/80 : 122,000 BTU
COP, Standard Rating Conditions 80/80/80: 6.3
BTU Output 80/80/63 : 110,000 - 119,000 BTU
COP 80/80/63 : 5.9
Model Specifications
Pipe Size: 2" FIP
Mode: Heat Only
AHRI Certified : 3694129
Fan Speed: 825 RPM
Fan Load Amperage : 1.8
Fan Motor: 1/3 HP
Refrigerant Type: R-410A
Refrigerant/Factory Charge: 4.4 lbs
Display Controls: Digital
Thermostat: Digital
Compressor: Scroll
Compressor LRA: 145
Compressor RLA: 26.9
Heat Exchanger: 100% Titanium
Plumbing Size: 2" Union

 

[Teald024]

Hello and Welcome to TFP!!
I skimmed this post and overall I agree with @ajw22 comments. The HP will use way more than $500 a season to heat the pool.
I don’t believe the pipe size has anything to do with the issues you are having. If you are running the pump on full speed, there should be no reason the flow isn’t enough to pull the heat out of the HP.
I don’t think it’s worth it to run larger piping, there just isn’t enough restriction in it to make a difference. Also, a 122k BTU heater is on the small side, there is no way that requires 90 GPM to work properly. You would only need 25 or 30 GPM to close the switch and operate properly. I don’t think running on low speed will give you enough flow to close the flow switch.

As a side note, be very cautious about using motor size to estimate pump flows. I had a Hayward pump with a 2 horsepower motor and a “1 horsepower“ impeller in it. The motor was just severely oversized for the impeller. It was effectively a 1 hp pump. I would recommend installing the flow meter and also pulling the inlet shroud off the pump and looking to see what size impeller you had in there. It’s easy to pull the shroud and then you would know for sure what impeller you have.
Your setup sounds very similar to what I had based on your description of the pump, filter and the pressures you’re seeing.

 

[JKB121]

@ajw22 I used the Raypak calculator using the same selections as you did, except I added solar cover at night and used our rate for electric. It comes up at $467.00/season

 

[ajw22]

Confirm your electric rate is .06/kwh fully loaded. I don't see how you can run up $400/month in electric on your HP at that rate even if the HP runs 24/7.

My electric rate looks like it is 0.083/kwh. But after transmission charges and distribution charges it is really 0.153/kwh, about double.

 

[ajw22]

@ajw22 I used the Raypak calculator using the same selections as you did, except I added solar cover at night and used our rate for electric. It comes up at $467.00/seasonView attachment 173700

The Raypak calculator assumes an IG pool. As I said earlier your AGP does not have the ground to insulate the pool walls or piping. You have a lot more thermal heat loss from the AGP then the calculator assumes.

And it brings into question the efffectiveness of your solar cover.

 

[JKB121]

The Raypak calculator assumes an IG pool. As I said earlier your AGP does not have the ground to insulate the pool walls or piping. You have a lot more thermal heat loss from the AGP then the calculator assumes.

And it brings into question the efffectiveness of your solar cover.

I guess we are back to at least installing a few feet of 2" so I can put the flow meter in so we have some numbers to work with. I'm now curious about the temperature in and the temperature out but have no idea how one would go about measuring that. I assume the digital readout on the HP is the temperature in so it knows when to kick on.
As far as the electric rate, we have the ability to choose our provider in Western Pennsylvania and we have a 2-year contract. I will have to double-check the transmission rates.

 

[wireform]

The reading on the HP is temperature after being heated. The water before heating can be checked anywhere in the pool away from the return stream like in the skimmer via a pool thermometer.

 

[Dirk]

You'd need something like this (one with a waterproof probe):

https://www.amazon.com/Taylor-Digital-Cooking-Probe-Thermometer/dp/B00004XSC5/ref=sr_1_5?dchild=1&keywords=probe+thermometer&qid=1611597042&sr=8-5

You wouldn't want to use any readings off of anything in the HP, as any sensors in there might be part of the problem.

You'd measure the water at or inside the return, and then at or inside the skimmer. Using just one device eliminates any inaccuracy that could be introduced by using two.

 

[jseyfert3]

As far as the electric rate, we have the ability to choose our provider in Western Pennsylvania and we have a 2-year contract. I will have to double-check the transmission rates.

Yeah but that's just supply. When I lived in Illinois, my distribution costs were just about the same as electric if not more, for a total of about 10-11 cents/kWh. Your monthly electric bill should outline your total cost per kWh, but if your supplier is different than your distributor your bill should outline both supply and distribution costs separately. My current distributor is also my supplier, they don't split out cost of electric and distribution on my bill, but the total is 11.4 cents/kWh. On your bill you have to add up (and maybe subtract) all of the line items for price/kWh. This snippet of my bill is one of the fewest numbers of line items I've seen on a bill, I had close to ten line items I had to tally up in Illinois to get my total price/kWh.


I'd be shocked if anywhere in the US had under 10 cents/kWh, my understanding is the Midwest has some of the lowest rates around. Illinois has lots of nuclear plants, rest is coal with plenty of in-state reserves, and a growing number of wind farms too. Illinois is the 3rd-largest exporter of electricity among states in the US.