My spa is going to have 8 jets on a 2” return loop with 2” trunk to pad. I ideally want to be able to flow more than 10 gym per jet, but 2” is limited to 83gpm at 8fps. If I leave the 2” loop but change trunk to 2.5” and maybe Tee into loop to 2.5” does this let me get around 83gpm limit. Basically I’m wondering if the 83 gpm doesn’t apply to loop since, well it’s a loop, and not a straight run, thinking it would be highe, but not sure.
Max FPS return loop
- Thread starter czb182
- Start date
- Jul 21, 2013
- 53,118
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
How much more then 10 gpm/jet do you want?
You will probably get close with 2" pipe.
What can't you do 2.5" to the jets?
You will probably get close with 2" pipe.
What can't you do 2.5" to the jets?
It will be able to flow 10gpm, I just don’t like being limited by flow speed, since that’s 80gpm and max is 83gpm for 2”. Was wondering while they are building it if I had a way to raise flow ceiling without touching plumbing inside spa, just the trunk. They are doing gunite soon, don’t want to hold it up. I asked about doing 2.5” but they said all their pools are 2” and it works fine, and I didn’t push hard. Wondering if maybe I should make them redo in bigger pipe or not. If still limited by loop then no point I figure. I was thinking maybe since Loop flows two directions that flow velocity is half , but I really have no idea.
- Jul 21, 2013
- 53,118
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
When you say max is 83 gpm that is not a hard rev limit. The friction of the water in the pipe increases and the pump needs to work harder to try and get more flow. How much more you can go depends on the size pump you have. At some point things get maxed out between the pump power and the pipe friction.
What pump are you using?
Use a dedicated spa jet pump so water flow is not throttled by a filter and heater to get maximum jet performance.
What pump are you using?
Use a dedicated spa jet pump so water flow is not throttled by a filter and heater to get maximum jet performance.
That’s really good point regarding heater and filter, hadn’t thought about that. At 80 gpm it’s 10ft of head for filter and 15 for heater, that’s quite a bit of overhead. My contract is not for single pump, so I will have to ask if plumbing will support adding second maybe in future.
ik using a 2.7HP pump, so even without dedicated I still have some room, maybe 400 rpm to go, based on my calculation of 55 TDH for spa only mode.
I realize it’s not a hard limit, I just going by what’s allowed by code, for builder to do. I think pump can do 12 gpm, but can’t put it that way I’m assuming if going to exceed FPS limit on return. That’s why I’m wondering about return loop FPS, if someone has modeled that before. I’m guessing some hydraulic modeling software would answer question, but I don’t have.
ik using a 2.7HP pump, so even without dedicated I still have some room, maybe 400 rpm to go, based on my calculation of 55 TDH for spa only mode.
I realize it’s not a hard limit, I just going by what’s allowed by code, for builder to do. I think pump can do 12 gpm, but can’t put it that way I’m assuming if going to exceed FPS limit on return. That’s why I’m wondering about return loop FPS, if someone has modeled that before. I’m guessing some hydraulic modeling software would answer question, but I don’t have.
- Jul 21, 2013
- 53,118
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
If you want a dedicated jet pump you need to put in a second suction in the spa during the build. Impossible to retrofit it after.
Spa has dedicated suction and return line, so should be ok there for future
I’m still curious for original question if anyone knows. When you have a return loop, does the velocity of water drop in half after Tee, remain dame, or drop by some other amount
I’m still curious for original question if anyone knows. When you have a return loop, does the velocity of water drop in half after Tee, remain dame, or drop by some other amount
- Jul 21, 2013
- 53,118
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
- May 3, 2007
- 16,993
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
A TEE that is looped around the spa and connected in the back AND each half of the TEE is exactly the same with the same number of jets on each side of the loop will have approximately the same flow rate going through each half of the TEE which means the total flow rate is split in half at the TEE. However, that rarely happens in practice although it won't be too far off. Each jet peels off part of the flow and ideally you have nothing going through the loop connection in the back. If you do, then there is an imbalance in one of the halves and the flow through each individual jet will vary some. Note that the larger the spa loop pipe, the less necessary it becomes and the more equal the jet flow will be.
How many jets are you planning and are they all 10 GPM jets? I would not use anything less than 2.5" pipe for a spa and perhaps more for a large number of jets.
Also 2" pipe is not limited to 83 GPM. It is only recommend to be below that.
How many jets are you planning and are they all 10 GPM jets? I would not use anything less than 2.5" pipe for a spa and perhaps more for a large number of jets.
Also 2" pipe is not limited to 83 GPM. It is only recommend to be below that.
- May 3, 2007
- 16,993
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Actually loops do not work all that well. They help but it is far better to go with larger pipe as insurance.
With 8 x 10 GPM jets, I would definitely not go less than 2.5" pipe. Remember you are stuck with whatever is installed.
they turned me down couple of times but finally relented and put 2.5” for return for probably 75% of the run. Gunite already done so they did as far as they could. Spa loop and maybe 20 feet of pipe are 2”.