Secondary (water feature) pump selection

[tonygiotta]

So, kinda last minute I decided I wanted to add a pair of deck jets to my new pool design. My PB suggested if I was going to add two, why not four as the plumbing would already be in place and the additional jets would add very little to the price? One thing led to another and now I am going to have 4 deck jets, a dedicated wall suction in the pool, and a high flow return to my spa floor so I can operate the spillway without the added noise and water turbulence of running the spa jets. This is all to be run on it's own separate plumbing by a (I'm assuming Pentair) VST pump.

In the forum reading I've done, I've noticed that different types of pumps are usually recommended depending on whether the goal is high flow (spillway) or high pressure (deck jets). So my question is, is a VST pump the correct choice to run both of these types of water features? Individually and/or at the same time? The deck jets are rated at 4.5gpm and 16' of head each. The spillway is a sloped negative edge and is going to be approximately 6' wide so (I'm assuming) about 60gpm and unknown head on the return line feeding it.

 

[mas985]

The VST should be able to run both at the same time although you will probably need to restrict the flow to the spillover at the same time ramping up the speed of the pump. Also, with a single pump, you wont be able to run the deck jets at the same time you are using the spa. So if you want the deck jets to run during pool mode or spa mode, you might be better off with a separate pump.

 

[tonygiotta]

Yes. This will be a secondary pump for the water features, primarily to allow for the use of the deck jets while the spa is on. Being able to run the spa spillway without flowing water through the spa jets is just a secondary benefit. Sorry if that was unclear.

Primary pump (also a Pentair VST) will be running filter/heater, pool returns, and spa jets. So would you recommend installing a gate valve at the equipment pad for the spa floor return? And to reiterate my original question, is the VST the right pump to use as a secondary pump for these two water features? My hope is that I'll be able to program the VST to run at a certain speed for the spillway, another speed for the deck jets, and a third speed when both features are active. Just wasn't sure how the balance was going to work out given the different head pressures of the two systems. Guess I'll have to wait and see just how magical these variable speed pumps are!

 

[mas985]

So would you recommend installing a gate valve at the equipment pad for the spa floor return?

You will have to have one in order to isolate the spa. Otherwise you would be spillover heated water into the pool when you are using the spa.

And to reiterate my original question, is the VST the right pump to use as a secondary pump for these two water features?

A bit overkill but yes it would work fine.

 

[tonygiotta]

You will have to have one in order to isolate the spa. Otherwise you would be spillover heated water into the pool when you are using the spa.

An actuator valve controlled by the ET8 panel will take care of that problem. The gate valve would just be to help equalize the head between the spillway and deck jets when they're both running as water features at the same time.

A bit overkill but yes it would work fine.

That's what I figured, but aside from going with the 10gpm per foot of negative edge spillway rule of thumb, I really don't know what the actual flow requirement will be to get the spillway effect I want. Better overkill than under I guess...

 

[mas985]

I really don't know what the actual flow requirement will be to get the spillway effect I want. Better overkill than under I guess...

You can use the waterfall equation:

https://www.lmnoeng.com/Waterfall/waterfall.php