Pump size and power

[dhamigs]

Hello I am building a 30’x20’ swimming pool with half at 4’ and other half at 6’ deep. My filtration system is going to be 400’ away and it’s downhill as well. There will be two 90s and 1 - 45 on the way from pump to pool.
What size pump will be a safe bet ??

 

[JamesW]

Equipment Pad Best Practices - Further Reading

www.troublefreepool.com

 

[JamesW]

My filtration system is going to be 400’ away and it’s downhill as well.

How much downhill?

The distance is not an issue if you size the plumbing correctly.

How much flow do you need and why?

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.

Pipe Size	6 ft/sec	8 ft/sec
1.5"	38 GPM	51 GPM
2"	63 GPM	84 GPM
2.5	90 GPM	119 GPM
3.0"	138 GPM	184 GPM
4.0"	235 GPM	312 GPM

As long as you keep the head loss down to about 8 feet or lower on the suction, you will probably be fine, but you need to know your maximum flow rates.

How many skimmers?

Skimmers should not typically be designed to handle more than 50 GPM, so a 2.5" line will be about 7.2 feet of head at 50 gpm for 400 feet.

If you have 2 skimmers, you can get up to 100 gpm if you have a separate 2.5" line from each skimmer to the pump.

I would probably design the skimmers to have a maximum of about 40 gpm as a good design practice.

Hazen-Williams Friction Loss Equation - calculating Head Loss in Water Pipes

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

 

[Jimrahbe]

d,

If you are like me, and just to lazy to figure all that out, just buy a 3 HP IntelliFlo3 and adjust it to meet your needs...

You can never go too big when using VS pumps...

Pentair IntelliFlo3 VSF 3.0HP with Touchscreen

If you plan to get some type of pool automation system, then you need to get the same brand pump as your automation, so that they can talk with each other.

Thanks,

Jim R.

 

[JamesW]

The main thing is to make sure that they do not undersize the suction lines.

At 400 feet, the pump can easily cavitate with 1.5" or 2" lines.

In most cases, you will probably never need more than 40 gpm, but it depends on what features etc. you want and how much flow you need for everything.

A 3 hp variable speed pump is a good choice.

What brand of equipment does the builder use or do you have a preference?

 

[JamesW]

If you have a 2" suction line, the maximum flow at 400 feet of pipe is about 29 GPM for a design to keep the head loss to below 8 feet.

 

[JamesW]

My filtration system is going to be 400’ away and it’s downhill as well. There will be two 90s and 1 - 45 on the way from pump to pool.
What size pump will be a safe bet ??

Most people think that they need a bigger pump if the filter is far away.

However, the pump size is the same regardless of how far away the pool is from the filter system.

What matters is the plumbing size.

The pump can be 1 foot or 1,000 feet away and the pump size will be the exact same.

You only change the pipe size and especially on the suction since it can cavitate.

 

[JamesW]

For example, if the flow is 62 GPM and you have 100 feet of 2" PVC pipe, the head loss is 8 feet.

If you have 1,000 feet of pipe, you have to increase the pipe size to 3.21" to get the same head loss.

From the pump's point of view, it requires the exact same amount of power either way.

The power required is based on the head loss and the flow rate in GPM and not the distance.