Pressure Question

tagprod

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Jul 3, 2007
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Tomball, Texas
pattonpool.com
#1
When the main pump is running, the pressure gauge on my cartridge filter reads 20 PSI. When I switch to spa mode (also ran by the main pump) the PSI jumps to 29. I cleaned the filer, but I got the same results. Anyone know why?
 

duraleigh

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#2
tag,

By switching to spa mode, you increase the resistance to waterflow on the pressure side of the system. When the resistance is increased, the pressure goes up.

Conversely, you could restrict the suction side of the pump (not that you want to...in fact, you DON'T want to) and the pressure would go down.
 

tagprod

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Tomball, Texas
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#3
Thanks Dave. By "resistance to waterflow" do you mean only drwaing water from the two main drains at the bottom of the spa in spa mode verses in pool mode where you have two skimmers 4 main drains and a suction side cleaner?
 

duraleigh

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#4
Those are all on the "suction" side of your pump. Resistance (friction) on the suction side decreases pressure on your guage.

The increase in pressure you are seeing is because of the increase in friction on the "pressure" side of the system....basically from the pump impellor 'til the water gets back in your pool
 

mas985

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May 3, 2007
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#6
tagprod said:
When the main pump is running, the pressure gauge on my cartridge filter reads 20 PSI. When I switch to spa mode (also ran by the main pump) the PSI jumps to 29. I cleaned the filer, but I got the same results. Anyone know why?
I don't want to be too alarming but a 9 PSI rise seems pretty large to me. That is over 20 feet of head! I would expect less than 4 PSI rise between a spa and pool but it depends on what the spa plumbing is. Has it always been like this?

Could you describe your plumbing in a bit more detail?

Pump model/HP
Pipe size for pool and spa
# pipe runs from pad to pool and spa
# returns for pool and spa (i.e. jets or returns depending on what the filter pump drives for the spa mode)
 

tagprod

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Jul 3, 2007
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Tomball, Texas
pattonpool.com
#7
It's a Heyward 2HP Northstar. I'm not certain on the plumbing size.

There are 5 returns for the pool and 6 jets on the spa.
Pipe rune? I'm looking for a pic but I can't find one. Here is the Rebar stagewith the plumbing on the spa



the equipment pad is much closer to the spa returns than some of the other returns. the little box connected to the left side of the house is the eq pad. The pool is 34 feet long for a point of reference

 

mas985

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#8
Your signature says 1.5 HP but your post says 2 HP?

Anyway, from your pictures, everything looks ok to me. The higher pressure is probably due to the type of jets you have in the spa. Some require pretty high pressure.

If the jets feel pretty strong, then I would not worry about anything.
 

tagprod

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Jul 3, 2007
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Tomball, Texas
pattonpool.com
#9
It's 2 hp - I thought it was 1.5 when I put the sig together. I'lll have to fix that. The jets are pretty strong. I never looked at the pressure gauge in spa mode - because I'm usually getting in and I thought it would be the same. As the pool pressure rises will the spa rise accordingly?
 

tagprod

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Jul 3, 2007
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Tomball, Texas
pattonpool.com
#11
not to keep asking dumb questions, but if the pool operates at 20PSI and the spa at 29 PSI can I still wait until the pool is at 28PSI before cleaning or should I clean it when the spa rises a couple of PSI higher say to 31? I don't have the literature in front of me, but I'll read that too tonight.
 

JasonLion

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#13
You want to clean/backwash when there is an 8 to 10 PSI increase in pressure in the same mode that you noted the starting pressure in. If you note the starting pressure in pool mode, then wait till you reach the increased pressure in pool mode.

There is no such thing as a dump question. Asking questions is how we learn.