Pump replacement

[rlvogel322]

I currently have a WhisperFlo 1.5 full rated pump that I would like to replace with a 2 speed pump. Going through Pump Education I have a feeling our current pump is oversized (no surprise there).

You can see in my signature that we have a 35k pool with a TA60D sand filter. According to Pentair the max flow rate through the filter should be 60 gpm. The pad is is plumbed with 2" with 2" headers for the suction and returns. The returns are three separate 1.5" runs (60') and the suction includes 2 spearate 1.5" (40') runs for the skimmers and 1 1.5" run for the main drain (40' length 8.5' depth). No solar or water features.

Looking at pump curves I am not sure what I should be using for head loss of our system. I think we can use a 1hp 2 speed pump but am not sure what the most efficient pump would be.

Thanks for any help.

 

[duraleigh]

Actually, the pump is not too terribly oversized but the filter is quite small for that size pool (I know that's not what you wanted to hear)

I would guess a head loss of about 40 might be pretty close for that pool (which is very adequately plumbed).

Mas985 has a very useful quick formula for calculating that by knowing your filter psi and it's on this forum but I searched and didn't locate it. I'll bet he will be along soon to help.

I'm sure you're not in the market but a filter size of around 100gpm would better match your pool size and the 1HP 2-speed would likely be a good fit for that.

 

[mas985]

Based on the information you gave, I estimate that the current operating point should be around 101 GPM @ 56' of head. Is the filter pressure around 19 PSI? Turnover is almost 6 hours.

If you went to at 3/4 HP two speed, WFDS-3, the operating point would drop to 82 GPM @ 38' of head and a 7 hour turnover.

If you want to plot your plumbing curve over the pump's head curve, you can use the following approximation:

Head = 0.0055 * GPM^2

The intersection of the plumbing curve and head curve is the operating point.

 

[rlvogel322]

Based on the information you gave, I estimate that the current operating point should be around 101 GPM @ 56' of head. Is the filter pressure around 19 PSI? Turnover is almost 6 hours.

If you went to at 3/4 HP two speed, WFDS-3, the operating point would drop to 82 GPM @ 38' of head and a 7 hour turnover.

If you want to plot your plumbing curve over the pump's head curve, you can use the following approximation:

Head = 0.0055 * GPM^2

The intersection of the plumbing curve and head curve is the operating point.

Wow! You're model is right on. We ran around 18 PSI clean last summer. Doing some additional research shows we are not really getting good filtration with that much GPM.

The safety cover helps but I am going to look at replacing the filter and pump at the same time.

Thanks for the quick feedback!

 

[mas985]

Wow! You're model is right on. We ran around 18 PSI clean last summer. Doing some additional research shows we are not really getting good filtration with that much GPM.

That is especially true with a sand filter. The dirt can get easily pushed through the filter.

Also, I forgot to mention that the numbers I posted for the WFDS-3 were for full speed. Half speed is about 41 GPM with a 14 hour turnover. With the Whisperflo series, half speed uses about a quarter the power as full speed so even though you have to run it twice as long, the energy savings is still 50%!

 

[rlvogel322]

If you want to plot your plumbing curve over the pump's head curve, you can use the following approximation:

Head = 0.0055 * GPM^2

The intersection of the plumbing curve and head curve is the operating point.

Is the constant 0.0055 for my specific plumbing? Meaning, can I use this equation on any pump curve for any manufacturer?

I am thinking the 2 speed will be the plan for this summer with a possible filter replacement next summer. I want to see if a new pump will make the water sparkle even more.

 

[duraleigh]

I want to see if a new pump will make the water sparkle even more.

Perhaps it will help if your old pump is actually pushing the dirt through the filter (possible with your setup)

However, water quality issues are from incorrect water chemistry about 95% of the time if not more. I woudn't buy the pump to clear up the water, you may be disappointed. I would buy the pump to save on electricity and get your system operating more efficiently.

 

[mas985]

If you want to plot your plumbing curve over the pump's head curve, you can use the following approximation:

Head = 0.0055 * GPM^2

The intersection of the plumbing curve and head curve is the operating point.

Is the constant 0.0055 for my specific plumbing? Meaning, can I use this equation on any pump curve for any manufacturer?

I am thinking the 2 speed will be the plan for this summer with a possible filter replacement next summer. I want to see if a new pump will make the water sparkle even more.

Yes, the constant was for your plumbing setup only. The equation just makes it easier to plot over any pump head curve to find the operating point.

 

[rlvogel322]

I want to see if a new pump will make the water sparkle even more.

Perhaps it will help if your old pump is actually pushing the dirt through the filter (possible with your setup)

However, water quality issues are from incorrect water chemistry about 95% of the time if not more. I woudn't buy the pump to clear up the water, you may be disappointed. I would buy the pump to save on electricity and get your system operating more efficiently.

Make no mistake, I found this site in 2007 because of water quality issues and have preaching it since then :-D. TFTestkits also.

My main reason is to save money on energy costs this summer. If I get an even better sparkle with more effective filtering all the better .