Pump too big or pipes too small?

Darcfa123

New member
Aug 27, 2016
4
MA
#1
First time here looking for confirmation of my research or a different opinion. I've read the Hydraulics 101 post (which, by the way, is outstanding) and gone through all the calculations on the detailed spreadsheet. It comes up with TDH=56 and GPM=63. For 19k pool and 6hr turn I need at least 53gpm. Where I'm stuck is on velocity. Guidelines indicate a maximum flow rate rate of 38gpm on suction side at 6fps. If the target flow rate is supposed to be between the turnover minimum and the velocity maximum, then the math doesn't work. The plumbing is 1.5", which I suspect could be the issue. I hope not. What am I missing here? It ran for 2 months last fall after being installed and didn't blow up. Maybe I've been at it too long now and my brain is fried. This all started because I want to install a heat pump and I wanted to make sure the flow rate was compatible.

On secondary note, it also seems the filter is too small based on the guidelines. The S220T has 2.6sf of effective filter vs. at least 3.6sf recommended for my size pool.


Forgive me I've just overlooked something obvious. New Pool Owner.

Thanks
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,258
Pleasanton, CA
#2
Welcome to the forum!

First, forget about turnover. It just doesn't matter and not a very good metric for determining run time or anything else. The 6 ft/sec recommendation on the suction side is for entrapment purposes. Is that a concern for pool? Is there a single MD where ALL the flow rate would be coming from? If you have multiple suction lines don't forget that flow is going to be split between them.

As for the filter size, how often are you cleaning it? I wouldn't get too concerned with the flow rate because sand filters are a bit more robust and should be able to handle that.
 
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Darcfa123

New member
Aug 27, 2016
4
MA
#3
Thanks Mark. After walking away from the issue for a while I realized that didn't need to worry about about turnover time much. I'm still a little curious if the pump is bigger than I really need. Electric bill went up a lot last fall after the pool went in. I'm going to put in a pressure gauge at the pump and try and get more accurate measurements.
 

scooperhsd

Well-known member
May 10, 2009
395
Youngsville NC
#4
In most case, you don't need to run your pump 24 hours a day, so I'd start off by putting my pool pump motor on a timer. Cut the time in half, let it run for a couple days, and see if it is still acceptable to you. If it is, cut in half again, repeat. I probably would not go below 3-4 hours / day with a single speed pump. If you are using a SWG, you need to run your pump enough to generate an adequate amount of chlorine to keep the pool clean, this may mean making adjustments on it to to increase the output for a given runtime. Yes, a 1.5 HP pump might be a little large, but I would not go replacing it just because of that either. Just keep it in mind when it comes time to consider a replacement. You might also want to consider 2 speed or variable speed pumps / motors to help cut down power use.

as for filter size - the general consensus is that there is no such thing as a too large pool filter. That said, a smaller filter just means you will need to backwash it more often. The TFP recommendation is to backwash when your pressure is 25% higher that when it was first cleaned - so if your "just cleaned" pressure is 16 PSI , Back wash at about 20 PSI. (Those figures are from my pool from past years - it typically changes when you change something, like a different pump, filter, add a heater, etc.)
 
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Darcfa123

New member
Aug 27, 2016
4
MA
#5
Much obliged for the response. I was coming to the same conclusions that you mentioned, so I'm glad to have some confirmation from experienced pool owners. I noticed you have the next size up Hayward filter as I do for the same volume (19k). But, it seems that I can go a while "as is" and maybe eventually replace it with something a little larger.
 

scooperhsd

Well-known member
May 10, 2009
395
Youngsville NC
#6
You'll find a great deal of pool knowledge here - take advantage of it. Eventually , you'll be contributing as well. I moved into my house with the pool 20 years ago - and I'm still learning things about it and better ways to do things.

For example - I live in a forest. I shutdown my pool sometime in October / early November - just be sure to get the cover on before the leaves start falling. This leads to leaves gathering on the cover, and of course accumulating rainfall and other precipitation. This makes for an "interesting" time when it's time to remove the cover (i.e this last weekend for me) . After several years of having dumped leaves and dirty water into the water, we hit upon the idea of removing the leaves AND pumping out the water from the cover before trying to pull off the cover (a small army can't remove a cover without making a mess if it is full of leaves and water, but just the wife and me remove it with out making a mess if we empty it first).