Pump for “Sheer” Descents Above 3 Feet?

[Nochka]

We have four 24” sheer descents with a dedicated 1.5HP Jandy FloPro pump (Model FHPM1.5). The pump has failed and needs to be replaced.

When replacing the pump, we are hoping to address a shortcoming of the original installation. The original 1.5HP pump was powerful enough to project the waterfalls 12-18” from the wall. However, the "sheer" stream of water broke apart about 12" above the pool's surface, causing the features to be very loud — too loud to hold a conversation near the pool. Notably the sheer descents are 44” above the pool’s surface, and I believe that 36” is the max recommended height.

I am wondering whether a larger water-fall-type pump might nonetheless provide enough flow to prevent the stream from breaking apart even from 44”, or if we’re out of luck. (The sheer descents are built into a stone wall and impractical to relocate.)

The four 24” sheer descents are plumbed with 2” pipe on both sides. The intake is about 20’ from the pump and the furthest sheer descent about 55’. On the discharge side the pipe briefly narrows to 1.5” where a Jandy Energy Filter is installed.

Thanks in advance for any recommendations, and particularly for any specific pump suggestions.

 

[JamesW]

A 2" suction line on a high flow water feature is not good. It creates too much restriction.

2" suction should be limited to about 62 gpm max.

3" pvc is good up to about 135 gpm.

A dedicated waterfall pump might be a good choice.

WaterFall™ Specialty Pumps

A variable speed pump will give you more control over the flow.

The Intelliflo xf would give you the most flexibility, but it's more expensive.

How much total flow are you looking for?

Note: Higher flow might give you a solid sheet to the water but it's not guaranteed if the waterfall is too high.

 

[Nochka]

Thanks James.

Replacing the 2" suction line would be impractical, but it's good to know that's undersized.

Regarding flow rate, I have read that 1 GPM per inch is a good rule of thumb. That would suggest 96 GPM, but presumably I should aim higher to compensate for the unusually high installation.

Makes sense to choose a large, variable speed pump for greater flexibility. I notice the Itelliflo XF has an onboard control system. Would it be better and cheaper to choose a pump without one, since I have a separate Hayward ProLogic control system?

 

[JamesW]

12 gpm per foot is typical. So, 96 gpm would be a target for 8 feet of 36" high sheer.

A higher sheer would require a higher flow rate to maintain a solid sheet to the water.

20 gpm per foot is the high end, which would require 160 gpm. However, that would require 4" pipe.

Your plumbing really won't support the flow you would need to maintain a solid sheet.

You can try a single speed water feature pump. The AFP-120 Might work but you would probably have to choke it back to keep it from cavitating.

The Hayward Tristar VS 2.7 HP should work with the ProLogic if you want to use a variable speed pump. That way, you can adjust the speed as needed until the flow is good or the pump begins to cavitate.

TriStar VS | Pumps | In Ground Pool Pumps - Hayward Pool Products

The Hayward Ecostar would also work, but it has bad reviews.

Check with Hayward to confirm that your Prologic is compatible with the Tristar as an auxiliary pump, especially if the Prologic is an early model.

 

[Nochka]

Very helpful. Thank you James.

Would it be smart to temporarily route the falls through my main pump, which is a 2HP FloPro? The goal being to see if a higher flow rate addresses the issue.

It’s a lot of extra work and perhaps a long shot given the underlying issue you identified.

 

[JamesW]

If you have a main drain, perhaps you could switch that to the sheer supply to give you extra capacity.

You can try putting the output of the main pump on the sheers to see if the extra flow helps.

You might be able to just run on the main pump without using a second pump.

If that works, you can tie in the sheer suction supply to the main pump and just use that.

 

[Nochka]

Thanks James. The main pump runs a spa as well as the pool, so unfortunately we can’t use it permanently. It seems like it may be worth running a test with it to see the impact of going from 1.5HP to 2HP. Then I can make a more informed guess as to whether the investment in a larger variable pump is wise.

 

[JamesW]

If you’re going to definitely use a separate pump for the sheers, then I would suggest that you take the pool main drain and use it with the original suction supply for the sheers to provide extra suction capacity. Then it would make it easier to get the full flow that you want.

As long as you have two skimmers, you should be fine switching the main drain from the main pump to the sheers. Then, the single speed water feature pump would probably work ok.

 

[Nochka]

I appreciate all the advice. For clarity I have only one skimmer. Is it possible to have the main drain feed both the sheers and the main pool/spa pump? Thank you.

 

[JamesW]

You really don't want to share a suction with two pumps.

Maybe just run everything on the main pump and just use valves to choose how to send the return.

You just wouldn't be able to use the spa and sheers at the same time.

 

[Nochka]

Thanks James. What you say makes sense. We do have an unused outlet on the main pump that used to run our Polaris (replaced with a robot). I could try running the falls off that and see if it's a good long-term solution. If not, I noticed one of the waterfall pumps you linked to (Pentair AFP-150) has 2" ports. I interpret that to mean it's likely to work with our 2" suction line. Would appreciate your POV on whether that's a good choice for my application. Thanks again for all the great advice.

 

[JamesW]

The AFP-150 might work since the suction line is relatively short.

If you were to put the unused line as an extra suction, it has to be done safely.

Submerged suction intakes need to have a certified cover and typically should be dual intakes or the cover should be certified as "unblockable".

For safety, it's generally recommended that the velocity in suction lines not exceed 6 ft/sec. For 2" pvc, that's 62 gpm.

If your current sheer suction intake is a single, you should make sure that it has a certified cover.

Increasing the suction too much can create an entrapment risk for underwater suction intakes.

Overall, the plumbing was never done correctly to allow the system to operate properly.

 

[Nochka]

Thanks James. For clarity I meant diverting the pool return that went to our Polaris to the sheers. We have dual drains with anti vortex covers on the spa, pool and sheers.

The simplest solution is obviously to replace the $200 motor on the pump and live with the noise. Wondering if I should do that and remove or replace the filter to improve the flow at the same time. I believe filters are required for sheers to prevent blockages, but the Jandy Energy Filter is a very small cartridge filter (3.2" diameter), and the 1.5" pipe is presumably also reducing flow.

Is there another product that could protect the sheers while minimally reducing the flow? The FloPro pump does have a strainer basket.

 

[JamesW]

The FloPro pump is not a low head pump, so it actually benefits from some added head loss on the return side.

The filter probably doesn't create a drastic loss. You could go to a big cartridge filter, but it's probably not worthwhile.

The slit on the sheers is fairly narrow, so it needs to be protected from minor debris, like small rocks and such.

Replacing the motor is the easiest solution.

The AFP-150 might work for you, but I don't think that you will be able to get a solid sheet of water that makes it to the pool without breaking up.