For my in-ground swimming pool, I recently had installed a new 48 sq. ft. DE
filter system with a new 1 hp pump. Suction piping from pool is 1.5 inch
swaged up to 2 inch at pump inlet. When operating on the first day, air
bubbles were in the pump strainer basket and a loud rumbling noise was
coming from the diverter valve. No air bubbles were visible in the pool
I had the repair guy come back out. His diagnosis - the pump was too close
to the pool (it's about 15 ft. away) such that too much water was being
sucked in by the pump. His remedy - downsize the pump impeller. I told him
that according to the pump ooperating manual, the pump should be located as
close as possible to the pool to cut down on resistance and friction. But
that clearly fell on deaf ears.
He also said that I should keep the vacuum plate cover off the strainer
basket and only use the cover when vacuuming the pool. Is this guy feeding
me a line or what?
Could what I think are air bubbles be turbulence instead?? I did notice
after the downsizing and after a couple of days air bubbles still swirl in
the strainer; like before, no bubbles are getting back to the pool. The
noise at the valve isn't as noticeable and sometimes is nonexistent, and the
pump does not lose prime when not operating. Since new system cost me
$1,500, I want to make sure it works right and I get my money's worth!
15 feet isn't realy that close to the pool. It is fine at 15 feet and the
distance doesn't matter anyway. The 1-1/2 inch return line sucks the same at
any distance. If you were say 3 feet from the suction port on the pool it would
still suck the same amount. As far as air bubles in the strainer basket go it
could be from a suction side leak only or from the strainer basket lid not
being secure. The pressure side leaks never take in air. Bleed the filter of
air and if the air keeps coming back turn the pump off and on and look for
water dripping out of the suction line. Also, you can hold a flame by the
suction side joints and see if the flame gets sucked in. Sometimes you can find
S-side leaks like that. I have even went as far as putting my ear on the pipe
to find it.
As far as the vacuum plate cover goes: Is that how you hook up the hose for the
vacuum? Most pools connect VIA a skimmer port. Anyway, I would put the strainer
lid that came with the pump on to make sure you aren't sucking air there Hon.
I am a CPO and have been into pools and spas for 19 years.
I think you have way too big of a pump, but it depends on your head
pressure. The 1.5" suction line will limit your max water flow to about 60
GPM (assuming it is PVC). Usually a 1/2 to 3/4 hp pump will easily get you
to 50 - 70 GPM. If your pump is trying to pull more than this through that
pipe, you may deteriorate it prematurely or even worse cause cavitation in
the pump. That could be the noise you're hearing and may be the source of
bubbles. The bubbles could also be from a suction side leak, so check the
pipe and pump fittings carefully, and strainer basket lid too.
The distance shouldn't matter too much, but you will pump less water with a
longer line. I think you may want to be pumping less water, however, this is
better done by adding a restriction to the output and not the input. An
inlet restriction will make cavitation worse. A smaller impeller would help
if the pump is oversized, but the proper size pump would be a better
I can see how you'd get slightly greater flow through the inlet pipe with
that plate removed, but the problem is the 1.5" inlet pipe itself and not
the 1.25" or 1.5" hole in the skimmer plate.
How big is your pool and how much water do you need to pump to circulate it
all in 6 to 8 hours? What is the max flow rate through your filter? What is
your operating head pressure at the flow rate you need -- do you have a
pressure gauge on the top of your filter? Without knowing all of this, you
cannot choose a proper pump.
I have a 3/4 HP pump on my pool, and I bought a flow meter to see what was
really going on. If I pump directly to waste, I get 75 GPM through my 1.5"
pipes and the pump cavitates terribly. Under normal operation, I get 50 to
60 GPM. As the filter gets dirty, it goes to 40 and even 30 GPM. If you look
at most pump curves, their flow rate is severely affected by head pressure.
If you don't spec it close, you could have greatly increased or decreased
You can test this excessive flow theory by closing off some of your pool
water inlets with rubber stoppers (or a few kids with hands). If you have a
gauge on your filter, close off water inlets one at a time and check the
gauge. If things quiet down and bubbles disappear as the pressure goes up,
you probably have found your problem. Do not exceed 35 PSI on your gauge
though, or you may damage things.
I'm considering a high head 1/2 HP pump as a replacement for my existing 3/4
HP pump. This pump will flow between 50 and 60 GPM under just about all
conditions of operation, from dumping directly to waste to a really dirty
filter. My filter pressure gauge currently reads 12 PSI when clean, and 20
PSI when really dirty.
So, if the 5 gallon bucket filled up in 27.4 seconds, that would be
10.948905 gallons per minute, or 656.9343 gallons per hour.
Ciperin' is as much fun as scratchin'. And doing both at the same time is
................. well, you know.
So how do you pump water in the bucket under the same head pressure as the
returns? My returns are under 18" of water and the wasteline has much less
resistance than the returns. The flow meter was only $50 and is always
there. Only mistake was putting it before the filter and it clogs
I did my measurements when the pool was filling.
I suppose in a filled pool you could just screw on some hose to the eyeball
fitting at the pool wall. If you wanted to get neurotic about accuracy,
you could calculate back-pressure for a length of such hose plus the
elevation to the bucket to equal the 18" (or whatever) water column you're
outlet pumps into.
Don't get me wrong. I would appreciate a gadget like a flowmeter. My
interest is just more in a one-time characterization rather than a day-to-
day performance monitoring.
Tom Bahama wrote, wondering if this is really what he meant?
A pressure test must have been done, in order to pass inspection, right? I
know the guys that did the plumbing on mine left that test on for what
seemed a week and the needle didn't move. When I built my pool, spa and
creek that runs into spa I used 2" throughout the whole deal, except a
reducer at the pool wall for the returns. I also used a 1 hp pump but my
filter station was about 50' from the pool. Around the side of the house
because I didn't want to see it or hear it. I had tons of valves to run the
different operations separately or all together. If I ever sell the house I
will have to write up a diagram for the new owner or they will never know
what the hell is going on. Anyway it sounds to me like your getting an air
intake leak causing the bubbles. You must have at least 2 intakes, the
drain at the bottom which should have two for safety and the skimmer. And
the skimmer has a built in valve you can adjust allowing the drain to work.
Have you tried to narrow it down to this area yet? Any wet spots in the
yard when you're not operating the pump? Do you remember the route of the
conduit to the pump. I know out here they have companies that can trace
down leaks. That might be an alternative. I just hope your problem isnt in
You can lead them to LINUX
but you can't make them THINK.
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