Is my flowrate correct for my filter?

[rjack1282]

I just bought a new home and am trying to get familiar with the equipment. There is a Hayward C12002 cartridge filter with a design flow rate of 120 GPM. I cannot find a brand name on the pump other than the motor is a 1.5 HP Marathon so I have attached a picture to see if anyone recognizes the manufacturer. My goal here is to make sure that I have an optimum flow rate for the filter so I can replace one or the other if not.

Thanks for the help.


IMG_4704 by rjack1282, on Flickr

 

[jblizzle]

Actually it is best to have low flow through your filter. And you have a pretty big pump and unfortunately a filter that is actually too small for your pool.

For a 21k gallon pool, you should have a filter at least 300 sqft and yours is only 120 sqft.

In an ideal world, you should get a larger filter and switch to a 2-speed pump so you can run on low speed for filtration and save money on electricity and only run high for vacuuming or the spa.

 

[linen]

Jbliz beat me...here are my comments:

The flow rate listed on the filter is a maximum flow rate and you really don't want to be operating even close to it. Filters filter better at lower flow rates.

As a side note, your filter is very small for your pool. Additionally, when you pump motor fails you will benefit by replacing it with a 2-speed motor (if it isn't already). That looks like a pentair challenger pump, if you post a picture of the motor label we might be able to tell you which one.

 

[rjack1282]

Thanks for the quick responses. Here is the label on the motor.


motor by rjack1282, on Flickr

 

[mas985]

My goal here is to make sure that I have an optimum flow rate for the filter so I can replace one or the other if not

Is something not working to your liking? Not ideal but if it ain't broke..............

Your pump looks to be a Sta-Rite 1.5 URHP Duraglas. The motor is a marathon which was probably a replacement at some point.

 

[rjack1282]

I just want to optimize the setup since I just moved. If changes need to be made, I want to make them now.

Would the filter being small for the pump explain why my clean filter pressure is at 18 psi? Or is it more complicated than that?

 

[mas985]

I just want to optimize the setup since I just moved.

But again, what do mean by "optimize"? This can be different for different people. For example:

Are you trying to lower energy bills?

Are you tired of cleaning your filter so often?

Is your filter getting damage and you are frequently replacing cartridges?


The primary reason your filter pressure is high is because you have a large pump trying force a high flow rate through the plumbing system. A cartridge filter's head loss (i.e. pressure loss) is dependent more on the design of the filter and not the size. But most have fairly low head loss. Sand filters are different where size makes a big difference.

A simple and cheap fix is to just replace the pump impeller with one of a lower HP rating (e.g. 3/4 HP). This essentially makes the pump a lower HP pump even though the motor is rated at a higher HP. A pump's motor current draw is dependent only on the load that the impeller imparts on the motor and has nothing to do with the motor's rating. The motor just needs to be big enough to handle the impeller load.

If you are trying to lower your energy bills, then an impeller change is an easy way to do that. If you want to lower your energy bills a lot, then a change to a two speed motor might be in order.

 

[rjack1282]

By optimize I mean correct sized filter for my pool (Jason mentioned it was too small) and the most energy efficient pump for pool and spa. I don't mind cleaning the filter often and it doesn't appear to be getting damaged during the short time I've been here.

I like your suggestion of a two speed pump. Would you use the low speed for circulation/filtering and then high speed for spa use?

 

[mas985]

Our filter size recommendations is based upon several factors and one is being that you don't want to damage the filter but your flow rate is no where near that point so no worries there. The second factor is cleaning frequency. A larger filter doesn't need to be cleaned as often. I have a 420 sq-ft filter and I clean it once a year. But if you don't mind cleaning the filter as much as you are then there is no reason to change filters. But I would not change the filter unless there is a issue with it.

As for the pump, smaller pumps and two speed pumps use less energy. Again, if that is of interest, then there are several options.

#1 Downsize the impeller. This save 10-20% in energy costs.

#2 Downsize the impeller and motor (two speed). This can save more than 50% in energy costs depending on how you run the pump.

#3 If your current pump is getting long in tooth and you don't want to put money into it, you can replace the entire pump with a two speed or even a VS.

It just depends on your budget and goals.