Pump recommendations for Grotto water feature

[laszlof]

Assuming about 20 feet of head loss, the speed would be about 2,700 RPM to get about 100 GPM.

How much concern is the noise?

2,700 RPM is not horrible, but 2,400 RPM or below is better.

View attachment 521450

Not super critical. The equipment pad is around the corner and has a fence in front of it. As long as its not screaming its not a big deal.

I went ahead and ordered it, I like the idea of sticking with a VS pump for now, and this one wasn't too terribly expensive. Once I figure out what actual flow I'll need, I can choose to switch it out for one of the purpose built waterfall pumps if I need to. My pool is still under construction, so its a bit of guess work right now based on what the grotto builder recommends. This one will at least let me go anywhere up to around 120GPM if needed.

 

[JamesW]

The AF-180 runs at 1,725 RPM, which should be pretty quiet if the motor is in good condition.

The AF-180 is the same as the AFP-150 except that the AFP-150 has a strainer and the AF-180 does not have a strainer.

It is better to have a strainer to keep debris out of the impeller and out of the water feature.

The new main drain covers have pretty small holes, so the risk of debris is lower with the new covers than with the older style main drain covers.

Wall mounted main drains have less debris issues than floor main drains.

The AF-180 uses about 1,380 watts.

 

[laszlof]

the PD270 arrived today. Its a lot bigger than I expected! Supposed to be getting plumbing ran early next week. We're doing 2" for all the main system (skimmer, returns, etc) and 3" suction for the grotto pump, 2.5" return as suggested here.

There will be a main drain on the back wall to feed the grotto pump. I wanted to try and get it closer to the pump, but the layout of the pool and its seating area made that difficult. Plus, I didnt want it anywhere near where people would be jumping around.

 

[JamesW]

There will be a main drain on the back wall to feed the grotto pump.

What make and model of drain?

You need dual drains or a single "Unblockable" drain.

The distance is not a big deal as long as you size the pipe correctly.

You could put the pump a mile away from the pool and it would still work as long as the pipe was sized correctly.

52.8 X 0.08 = 4.22 feet head loss at 5,280 feet (1 mile) at 100 GPM using 6" diameter PVC pipe.

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

PVC Pipes Schedule 40 - Friction Loss vs. Water Flow

Water flow in thermoplastic PVC and CPVC pipes Schedule 40 - friction loss <i>(ft/100 ft, psi/100 ft)</i> and flow velocities at dimensions ranging 1/2 to 16 inches.

www.engineeringtoolbox.com

 

[JamesW]

If you do a single unblockable drain, use (2) 2" PVC lines from the 2 or 3 connection points and T into a 3" line.

32" Channel Main Drain (Drain Cover & Sump) - CMP

IAPMO LISTED MAX FLOW RATES PLUMBING PORTS FLOOR FLOW RATE WALL FLOW RATE 2.5″ OUTER 298 GPM 212 GPM 2.5″ CENTER 200 GPM 168 GPM 2″ OUTER 242 GPM 192 GPM 2″ CENTER 184 GPM 168 GPM Flow rate verified May 2011 to CPSC Test Protocol ... Read more »

www.c-m-p.com

AquaStar Pool Products | 32" Channel Drain Flat Grate Anti-Entrapment Suction Outlet Cover and PVC Three-Port Manufactured Sump Replacement

Use this online guide to help find a replacement for any AquaStar drain cover manufactured.

www.aquastarpoolproducts.com

 

[laszlof]

What make and model of drain?

You need dual drains or a single "Unblockable" drain.

Unsure on the make/model yet. I'm aware of the dual drain or "unblockable" requirement. It'll probably be a single drain with dual inputs like you posted above. My plumber is aware of the requirement and will source something from their distributor.

The distance on the suction size is around 55-60 feet from the drain to the equipment pad. 3" piping should still be fine here I would think.

 

[laszlof]

@JamesW That actually brings up a good point. Is there any downside to upsizing ALL of the underground plumbing? If I were to switch everything from 2" to 4", would it cause any issues outside of costing a bit more for material? The equipment pad would still be all 2" piping since thats what all the pumps/filters/heaters have connectors for.

In theory, doing this would allow me to run the pumps at a lower RPM to achieve the target GPM for filtration, chlorine generation, and heating. Correct?

 

[JamesW]

Upsizing the pipe always helps, but it is a case of diminishing returns.

As long as you follow the velocity rules, the pipe size should be good.

Going to a larger pipe won't make enough difference to be worthwhile.

 

[1poolman1]

@JamesW That actually brings up a good point. Is there any downside to upsizing ALL of the underground plumbing? If I were to switch everything from 2" to 4", would it cause any issues outside of costing a bit more for material? The equipment pad would still be all 2" piping since thats what all the pumps/filters/heaters have connectors for.

In theory, doing this would allow me to run the pumps at a lower RPM to achieve the target GPM for filtration, chlorine generation, and heating. Correct?

Its not "a bit more" for 4" plumbing. For example, 2" PVC coupler - +/- $1.25@. 4" PVC coupler for pressure applications (not DWV) - +/-$15.00@.
2" PVC Sched 40 pipe - +/-$1.75/ft. 4" PVC Sched 40 pressure pipe - +/- $8.00/ft. The adapters to get the plumbing to reduce to the pool equipment size from 4" are crazy-expensive as well. Then they will take at least 4X the amount of glue applied with a special roller to put together (you'll have to buy it by the gallon) and without the proper tools to force the pipe into a fitting it is very difficult to get a good glue joint.
The return in flow is not worth the cost unless you are talking huge commercial pumps, 5-20HP.