Maximum distance from pool equip to spa?

[RogerRoger]

We are in the process of building a new pool. It will have a raised heated spa on one end. What is the maximum distance from the pool equipment to the spa? The location we want to use would be 94'. The location the builder wants to use is 80'. I believe we are using a Hayward 950 VSP.

Any advice would be greatly appreciated.

Thanks!

 

[JamesW]

What will be the maximum flow rate?

Will the elevation of the equipment be above or below the spa and by how much?

For suction, you want to keep the water velocity below 6 ft/sec. For returns, you want to keep the water velocity below 8 ft/sec.

Size.......6 ft/sec......8 ft/sec.
1.5"...........38...............51 gpm
2"..............63...............84 gpm
2.5............90.............119 gpm
3.0".........138.............184 gpm

As long as the length is less than 100 feet and you follow the above rules, the system should be fine.

Over 100 feet, go up one pipe size.

To be conservative, you can use 6 feet per second for the return instead of 8 feet per second.

For returns close to 100 feet, I would suggest the following maximum flow rates.

Size.......Suction......Return
1.5"...........38...............45 gpm
2"..............63...............75 gpm
2.5............90.............105 gpm
3.0".........138.............160 gpm

 

[RogerRoger]

What will be the maximum flow rate?

Will the elevation of the equipment be above or below the spa and by how much?

For suction, you want to keep the water velocity below 6 ft/sec. For returns, you want to keep the water velocity below 8 ft/sec.

Size.......6 ft/sec......8 ft/sec.
1.5"...........38...............51 gpm
2"..............63...............84 gpm
2.5............90.............119 gpm
3.0".........138.............184 gpm

As long as the length is less than 100 feet and you follow the above rules, the system should be fine.

Over 100 feet, go up one pipe size.

To be conservative, you can use 6 feet per second for the return instead of 8 feet per second.

For returns close to 100 feet, I would suggest the following maximum flow rates.

Size.......Suction......Return
1.5"...........38...............45 gpm
2"..............63...............75 gpm
2.5............90.............105 gpm
3.0".........138.............160 gpm

I'm not sure what the flow rate will be. I would have to ask the builder that. But the equipment will be approximately 3 ft below the spa.

Thanks!

 

[JamesW]

If you follow the guidelines above, the distance is not a problem.

The equipment could be 1,000 feet away as long as the pipe is sized correctly.

For 1,000 feet at 138 gpm, you would change the pipe size to 5" and it would be about the same amount of resistance as 3" pipe at 100 feet.

 

[RogerRoger]

Treat me like an idiot, so my builder won't think I'm a complete idiot. I can take it. How is the maximum flow rate determined or calculated?

So the longer away the spa is from the equipment, the larger the pipe is needed?

I want to be able to say, hey why don't we step up the pipe size to make sure the water pressure going to the spa is strong enough. Or something along those lines.

 

[ajw22]

I don’t see why your builder is arguing with you about a 20% increase in length from 80’ to 94’. Whatever size pipe he was using at 80’ let him go next size up if there is doubt.

What you are getting into is the complex “head” calculations of what a specific pump can put out versus the friction losses caused by pipes and equipment. We can take you through that but it is your builder who should do it if in doubt.

Your simple request to him is do it at 94’ with a larger pipe If necessary.

 

[JamesW]

The flow rate depends on what you’re trying to do. For simple filtration, about 15 to 20 gpm is plenty.

For a heater, you want at least 10 gpm per 100,000 btu/hr of heating. For example, a 400,000 Btu per hour heater requires at least 40 gpm.

For spa jets, you multiply the number jets by the manufacturer’s flow recommendations for the jets. For example, 5 jets at 25 gpm per jet is 125 gpm for good action.

For a spa spillover feature, it depends on the width of the spillover and how thick you want the sheet of water to be. Typical flow is between about 5 gpm per linear foot for weak action to 20 gpm per linear foot for good action.

The pump can get up to 175 gpm at full speed (3,450 rpm) as shown in the below brochure with the pump performance curve. Realistically, the flow should not be designed to go above 150 gpm.

https://hayward-pool-assets.com/assets/documents/pools/pdf/literature/TriStar-VS-950-eLITTSVS95020.pdf

The flow depends on the pump speed and the total head loss of the entire system, which includes the suction pipe and fittings, the filter, the heater, any other equipment and the pipes going back to the spa and the jet fittings.

For high flow designs, get a cartridge filter with about 400 to 500 square feet of surface area.

The heater will be the largest head loss. If the flow will go above about 80 gpm, I would recommend a check valve bypass that allows some water to go around the heater instead of going through it.

For pipe, you can figure out the head loss using charts or a calculator like below.

Hazen-Williams Water Flow Formula: Head Loss, Data, Charts & Calculator

Friction head loss (<i>ft_H2O per 100 ft pipe</i>) in water pipes can be estimated with the empirical Hazen-Williams equation.

www.engineeringtoolbox.com

The calculator will tell you the head loss and water velocity when you enter the pipe size, pipe length and flow in gpm.

Many pieces of equipment will include a head loss curve in the brochure or installation manual so that you can figure out the specific head loss for each piece of equipment.

For example, the head loss for a cartridge filter is shown in the manual on page 9 where it has a graph of the head loss vs. the flow rate. For example, the head loss at 140 gpm is 14 feet.

If you can’t find a head loss chart for a specific fitting or piece of equipment, you can ask the manufacturer and they should provide it.

https://hayward-pool-assets.com/assets/documents/pools/pdf/manuals/SwimClear-Cxx30-revB.pdf

Standard code for pool plumbing is a maximum of 6 feet per second for suction and 8 feet per second for return plumbing.

Most localities will require this and the builder should follow these design rules.

 

[mas985]

We are in the process of building a new pool. It will have a raised heated spa on one end. What is the maximum distance from the pool equipment to the spa? The location we want to use would be 94'. The location the builder wants to use is 80'. I believe we are using a Hayward 950 VSP.

Head loss in that pipe will increase by only 18%. Much less when you look at the change in total head loss. Not even worth considering. Why does the PB want to use one location over another? It may be due to something else besides distance.

 

[RogerRoger]

The spa will be 6'x8' with 8 jets. The only reason the PB wants one location over beside the house is distance - his location saves about 14'. He's not real happy with his location being about 80' away, but the designer failed to take this stuff into consideration when designing the pool. He would prefer it be less than 70'. My desired location is beside the house. His location at 5' off the back property line which would require us to put heavy landscaping around it to hide it from neighbors.
We don't need to jets to provide therapeutic action. We just need it to provide enough bubbles for aesthetic purposes.

Thanks for all the info thus far!

 

[JamesW]

As long as the pipe is sized correctly, the distance really does not matter. The equipment can be 1,000 feet away and it does not take any extra effort for the pump as long as you increase the pipe size.

For 1,000 feet at 138 gpm, you would change the pipe size to 5" and it would be about the same amount of resistance as 3" pipe at 100 feet.

Follow the 6 feet per second rule and you should be fine.

If the flow was going to be more than 138 gpm or more than 100 feet away, you would change to 4" pipe for the suction.

 

[JamesW]

The spa will be 6'x8' with 8 jets.

We would need to know the model number of the jets to look up the flow required per jet.

For example, at 15 gpm per jet, the total flow would need to be 120 gpm.

That would require a 3" suction from the spa and a 3" return feeding the jets.

Will the spa suction be just from the main drains or will it also have a skimmer?

 

[JamesW]

Jet Setting - Water Shapes

Whether a spa is concrete or portable, custom or mass produced, sound hydraulics and good plumbing are needed if the spa’s jets are to give clients the hydrotherapeutic action they crave. The manufacturers of portable spas do this work for their dealers,

watershapes.com