Question about Pump/Sand Filter Sizing

[NTL1991]

Hello,

I've been having a bit of trouble keeping my pool clear and cloud-free, and I wanted to ask a question about pump and sand filter sizing.

I have a 24' round (45" of water) pool with a WMC Hydron F500 sand filter, and a Jacuzzi (can't read the model no.) pump with a 1.5HP Magnetek pump, I'm not sure as to the GPM of the pump. The filter lists the following specs:

Filter Area: 2.2 Square Feet
19.5 GPM/Square Foot
43 GPM
150lb of Media
Maximum Pressure: 37 PSI

The sand media was replaced last year when I replaced the multiport valve assembly. I'm concerned that the pump is too powerful for the filter, and the water is just being blasted through the media without actually being filtered.

I have a spare Jacuzzi Laser (L160, I believe) sand filter (that was blowing sand into a relative's pool), along with an identical Jacuzzi pump to mine, except it has a 1.0HP motor.

The filter seems to be a little big for the pool, which is fine, but I'm concerned about the pump.

Thanks,
Nick

[trickedout]

Are all your Chemical tests balanced and leading you to this conclusion? I think your pump is about right for your filter, Have you tried taking the return from the filter off and filling a bucket up with the filtered water? Maybe with that you will be able to see if in fact your pump is just blowing through the sand.. Not an expert but thought i would just try to give advise.

[Watermom]

Nick,
I think you are very likely right that a 1.5hp pump is too powerful for a 150lb. sand filter and is blasting stuff right through the sand bed. We see this a lot on AG pools. That is an awful big pump for a 24ft pool.

Welcome to the Pool Forum, by the way!

[NTL1991]

Thanks!

Would it be prudent to swap out the 1.5HP motor for the 1 horse? The pumps are identical, so I'd only have to swap the motor. Would that bring my GPM down closer to the limits of the filter? I have a feeling my wallet would feel a little better about it, too.

Thanks Again,
Nick

[PoolDoc]

Actually you'd might just burn up the motor -- the reasons get too complex to cover briefly. But, to accomplish what you want -- IF it's possible -- you'd need to swap the impeller, seal, and possibly diffuser. It wouldn't be necessary to change out the actual motor.

I'll ask Mark to look at it tomorrow, when I process your registration.

[mas985]

Sometimes people use the words pump and motor synonymously so I just want to make sure I understand completely. Are you proposing to swap JUST the motors or the entire pump with motor? As Ben pointed out, downsizing just the motor is a problem but if you swap the entire pump, that is ok.

Without any additional information, my guess is that pump is producing at least 65 GPM which is technically more than the filter can handle. A 1 HP Jacuzzi would be slightly better but still exceeding the 43 GPM spec. To get down to that flow rate, you will probably need the smallest AG pump on the market. Either a 3/4 HP Optiflo or Dynamo pump.

Can you post a picture of your current pump (entire pump, not a close up) just to make sure? Also, can you tell me the service factor off the pump label for each pump?

[NTL1991]

Sometimes people use the words pump and motor synonymously so I just want to make sure I understand completely. Are you proposing to swap JUST the motors or the entire pump with motor? As Ben pointed out, downsizing just the motor is a problem but if you swap the entire pump, that is ok.

Without any additional information, my guess is that pump is producing at least 65 GPM which is technically more than the filter can handle. A 1 HP Jacuzzi would be slightly better but still exceeding the 43 GPM spec. To get down to that flow rate, you will probably need the smallest AG pump on the market. Either a 3/4 HP Optiflo or Dynamo pump.

Can you post a picture of your current pump (entire pump, not a close up) just to make sure? Also, can you tell me the service factor off the pump label for each pump?

Sorry, for some reason I was thinking the motor was what would change the flow rate, but now I understand its not the motor but the impeller design. I'd have to swap the whole pump assembly including the motor.

Could I install the 1HP Jacuzzi Pump and then reduce the flow somehow to achieve the 43GPM? I know I wouldn't save much on electricity compared to switching to a 3/4 HP, but a new pump isn't in the cards for this pool. The supply and return piping is flexible, 1.5", I believe. Could a valve be installed to reduce the flow? Would that cause any longevity issues with the pump?

It's my aging parents pool and I'm the one maintaining it. They bought the pool for all the grand kids to use, but now all my siblings have their own pools. Right now, only my mother uses the pool, so I've been thinking about removing it and just getting a jacuzzi for her... Anyway...

Sure, I can get you a picture of the entire pump and the service factors next time I get over there.

Thanks,
Nick

[PoolDoc]

Sorry, for some reason I was thinking the motor was what would change the flow rate, but now I understand its not the motor but the impeller design. I'd have to swap the whole pump assembly including the motor.

Actually, if you are handy, all you have to do is change the impeller and the seal, and MAYBE the diffuser. You do NOT have to change the motor. You can run a big motor with a small impeller, and get almost the same electrical efficiency you would with a smaller motor. (Big impeller + small motor = SMOKE & FIRE!)

[NTL1991]

Interesting.

I don't have valves or anything on the supply and return tubing, so I'd have to drain off the water above the skimmer which isn't something I want to do at the moment. When I'm in the process of winterizing the pool, (which may be coming very soon, depending on my patience), I'll tackle the pump issue. I think I'd rather just swap the pump assemblies whole.

What is your opinion on hard-piping the pump and filter? Would that increase my flow rate, exacerbating the problem? I like the neat appearance, and the ease of adding valves and accessory items to the pool. Are there any good links here on proper piping layouts when hard-piping above ground pools? I'd imagine winterizing would be the prime concern with a hard-piped system.

Thanks,
Nick

[PoolDoc]

Hard PVC is not going to dramatically affect flow rates compared to same-size flex. I'm not sure about the issues of attaching rigid pipe to an AG pool wall, but I'd won't be really careful about that. You DEFINITELY do NOT want to create a stress point in the wall that way.