I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


"SW" wrote in message
news
I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

You don't say if this is a new set-up or one that has been functioning
properly in the past. If it is a new set-up, what size is the pump
inlet? Your piping should not be any smaller than that. If it had
been functioning OK in the past, I would check the intake line for any
blockages. Make sure the valves are completely open. Anytime a
vacuum is created on the intake side, cavatation can occur as a liquid
under a vacuum can become a gas. If there is a restriction on the
inlet line causing the pump to create a vacuum, a minor leak that
wasn't a problem previously can become a problem.


SW wrote in message . ..
I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

J. Douglas Mercer wrote:
Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


when I was in the fire dept our pumps would cavitate when they sucked
air instead of water, are you getting air bubbles at the output??

John Rutz
Z5 New Mexico
If it can't be fixed with bailing wire or duct tape
its not worth fixing

see my pond at:

http://www.fuerjefe.com

On the Sequence pump website there is some troubleshooting guidelines and I
remembered that it refers to cavitation problems and what to do. I have
copied that below.
Hope it helps.


With the pump running, slowly close down your valve on the discharge side of
the pump. If the noise goes away, then you were hearing cavitation.
Cavitation is caused when the pump isn't getting water re-supplied quickly
enough. To remedy this, you need to
1. Reduce the output by partially closing a valve on the discharge, until
you reach a point where the cavitation stops.
2. Increase the diameter of pipe on the suction of the pump.
3. Shorten the length of the pipe on the suction of the pump.
4. Reduce the numbers of elbows on the suction of the pump.
5. Lower the elevation of the pump.
Any one or combination of the above changes will help eliminate cavitation.

"J. Douglas Mercer" wrote in message
news:Vnpua.774319$L1.218044@sccrnsc02...
Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


"SW" wrote in message
news
I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

Would downsizing the pump be preferable to restricting outflow. Inflow
I will correct, but even then, if the pump was too high output it
would still cavitate. True?

On Thu, 08 May 2003 23:21:09 GMT, "Ted"
wrote:

On the Sequence pump website there is some troubleshooting guidelines and I
remembered that it refers to cavitation problems and what to do. I have
copied that below.
Hope it helps.


With the pump running, slowly close down your valve on the discharge side of
the pump. If the noise goes away, then you were hearing cavitation.
Cavitation is caused when the pump isn't getting water re-supplied quickly
enough. To remedy this, you need to
1. Reduce the output by partially closing a valve on the discharge, until
you reach a point where the cavitation stops.
2. Increase the diameter of pipe on the suction of the pump.
3. Shorten the length of the pipe on the suction of the pump.
4. Reduce the numbers of elbows on the suction of the pump.
5. Lower the elevation of the pump.
Any one or combination of the above changes will help eliminate cavitation.

"J. Douglas Mercer" wrote in message
news:Vnpua.774319$L1.218044@sccrnsc02...
Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


"SW" wrote in message
news
I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

The inlet on the pump is 2 inch. I have 2 inch plumbing everywhere
except for a sigle 1 foot length just prior to the pump which is very
expensive to eliminate ( I would lose $300 in valves alone) On the
outflow side there is also 2 inch pipe, except for the filter plumbed
with 1 1/2 inch, but I am going to change this anyway.

On 8 May 2003 06:24:17 -0700, (Cleveland
Ponder) wrote:

You don't say if this is a new set-up or one that has been functioning
properly in the past. If it is a new set-up, what size is the pump
inlet? Your piping should not be any smaller than that. If it had
been functioning OK in the past, I would check the intake line for any
blockages. Make sure the valves are completely open. Anytime a
vacuum is created on the intake side, cavatation can occur as a liquid
under a vacuum can become a gas. If there is a restriction on the
inlet line causing the pump to create a vacuum, a minor leak that
wasn't a problem previously can become a problem.


SW wrote in message . ..
I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from 15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before ,
and know little, but it sure seems like it to me.

no air bubbles in the pump or at the output

On Thu, 08 May 2003 07:55:47 -0600, John Rutz
wrote:



J. Douglas Mercer wrote:
Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


when I was in the fire dept our pumps would cavitate when they sucked
air instead of water, are you getting air bubbles at the output??

John Rutz
Z5 New Mexico
If it can't be fixed with bailing wire or duct tape
its not worth fixing

see my pond at:

http://www.fuerjefe.com

SW,

The pump impeller is probably cavitating as you
suspected, which means that the flow is restricted
enough from going from two inch piping to 1 1/2
piping and so is pulling a vacuum on the water and
beating the subsequent bubble that is created
making the noise. This is pretty much confirmed
since the sound goes away when you shut down the
discharge of the pump decreasing the flow
requiring the pump to push less through the lines
meeting the flow requirement for the 1 1/2 inch
lines.

In this instance you have two choices, either
replace the piping to the pump increasing the
diameter to 2 inches for all of your piping or buy
a new pump with less discharge capacity. I guess
there is a third choice and that is leave the
discharge shut down to the point where the noise
stops.

The thing that you have to remember, if the
cavitation is allowed to continue (I do not know
what kind of pump you have) there is a chance that
the cavitation will damage you impeller requiring
pump replacement or impeller replacement.

HTH

Tom L.L.
=============================
"SW" wrote in
message
news
I have an inground pool. 2 inch plumbing
throughout, except necked
down to 1 1/2 right before the intake to the
pump. The output goes
through a filter system which has pressure
gauges and then to the pool
return line (2 inch) and the spa return (also 2
inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs,
it sounds as if there
are bubbles in the intake line. NOT the pump
itself, but the intake
line leading to it. I don't see any air in the
pump or lines. When I
close off 1/2 of thr output by closing down the
pool return, leaving
only the spa line open, the presssure in the
filter line jumps from 15
psi to 22 psi and the noise in the intake
instantly stops. Open the
pool return line again, and the noise instantly
returns. Is this
cavitation? The motor seems to run hot, but has
had no problem putting
out flow or tripping breakers. What can I do? I
can't reasonably
change the intake to 2 inch without spending big
$$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never
seen cavitation before ,
and know little, but it sure seems like it to
me.

I agree. So, initially when the pool guys told me to get a 1 to 1 1/2
hp pump in order to circulate 70 gpm to filter my pool once every 8
hours (32,000 gal), I did just that. My problem was that I had a Full
rated 1.5 hp super II (the same motor as a 2 hp max rated), which put
out more flow than a 2.5 hp standard Super I pump--about 130 gpm at 40
ft of head!!! Way too much.

Today I went out and got a 3/4 hp FULL RATED (service factor 1.5)
super II pump.The motor is actually a 1 1/8 hp MAX rated motor for
comparison purposes. The super II pump itself, puts out 20% more than
a standard pump. A standard 1 1/2 hp max rated pump (service factor 1)
puts out 80 gpm at 40 ft of head, 67 gpm at 50 ft of head, and 50 gpm
at 60 ft of head. The 3/4 hp full rated high efficiency super II puts
out 78 gpm at 40 ft of head, 67 at 50 ft and 56 at 60 ft. Amazing that
the lower rated pump (horsepower wise) puts out the same flow as the 1
1/2 hp max rated pump, but it does. So I needed either a 1.5 hp
standard pump or the 3/4 hp full rated super II. I bought the later
because of it's 2 inch ports and higher energy efficiency.

Anyway,I am going to change the pipe to 2 inch where it was necked
down, and enjoy energy savings while not worrying about cavitation and
damaging my filters and lines. Ahh, but what about the spa jets? Will
I have enough oomph from that 3/4 hp pump to run the 6 jets? Maybe
not, but if that's the case, I'm merely going to put a valve in to use
my Polaris booster pump double duty. When I'm in the spa, I'll divert
the 3/4 hp polaris booster to the spa instead of the cleaner.

What do you think, will this work?

Steve

On Thu, 8 May 2003 16:49:56 -0500, "Tom L. La Bron"
wrote:

SW,

The pump impeller is probably cavitating as you
suspected, which means that the flow is restricted
enough from going from two inch piping to 1 1/2
piping and so is pulling a vacuum on the water and
beating the subsequent bubble that is created
making the noise. This is pretty much confirmed
since the sound goes away when you shut down the
discharge of the pump decreasing the flow
requiring the pump to push less through the lines
meeting the flow requirement for the 1 1/2 inch
lines.

In this instance you have two choices, either
replace the piping to the pump increasing the
diameter to 2 inches for all of your piping or buy
a new pump with less discharge capacity. I guess
there is a third choice and that is leave the
discharge shut down to the point where the noise
stops.

The thing that you have to remember, if the
cavitation is allowed to continue (I do not know
what kind of pump you have) there is a chance that
the cavitation will damage you impeller requiring
pump replacement or impeller replacement.

HTH

Tom L.L.
=============================
"SW" wrote in
message
news
I have an inground pool. 2 inch plumbing
throughout, except necked
down to 1 1/2 right before the intake to the
pump. The output goes
through a filter system which has pressure
gauges and then to the pool
return line (2 inch) and the spa return (also 2
inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs,
it sounds as if there
are bubbles in the intake line. NOT the pump
itself, but the intake
line leading to it. I don't see any air in the
pump or lines. When I
close off 1/2 of thr output by closing down the
pool return, leaving
only the spa line open, the presssure in the
filter line jumps from 15
psi to 22 psi and the noise in the intake
instantly stops. Open the
pool return line again, and the noise instantly
returns. Is this
cavitation? The motor seems to run hot, but has
had no problem putting
out flow or tripping breakers. What can I do? I
can't reasonably
change the intake to 2 inch without spending big
$$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never
seen cavitation before ,
and know little, but it sure seems like it to
me.

If your outflow pipe is larger than your inflow your going to end up with
cavitation unless you can reduce the outflow. If you have a piece of smaller
diameter on the inflow than what is on the outflow it would be easier and
cheaper to put a valve on the outflow . It does not hurt a pump to restrict
the outflow, you dont want to restrict the inflow however.

"SW" wrote in message
...
Would downsizing the pump be preferable to restricting outflow. Inflow
I will correct, but even then, if the pump was too high output it
would still cavitate. True?

On Thu, 08 May 2003 23:21:09 GMT, "Ted"
wrote:

On the Sequence pump website there is some troubleshooting guidelines and
I
remembered that it refers to cavitation problems and what to do. I have
copied that below.
Hope it helps.


With the pump running, slowly close down your valve on the discharge side
of
the pump. If the noise goes away, then you were hearing cavitation.
Cavitation is caused when the pump isn't getting water re-supplied
quickly
enough. To remedy this, you need to
1. Reduce the output by partially closing a valve on the discharge, until
you reach a point where the cavitation stops.
2. Increase the diameter of pipe on the suction of the pump.
3. Shorten the length of the pipe on the suction of the pump.
4. Reduce the numbers of elbows on the suction of the pump.
5. Lower the elevation of the pump.
Any one or combination of the above changes will help eliminate
cavitation.

"J. Douglas Mercer" wrote in message
news:Vnpua.774319$L1.218044@sccrnsc02...
Don't know.
Interesting topic though.
Cavitation refers to a "cavity" when the upstream pressure exceeds the
ability of the ambient pressure to fill the vacancy.
Mostly used in submarines, though, sometimes aircraft.
"Drag" might be a better word for it with aircraft.


"SW" wrote in message
news I have an inground pool. 2 inch plumbing throughout, except necked
down to 1 1/2 right before the intake to the pump. The output goes
through a filter system which has pressure gauges and then to the
pool
return line (2 inch) and the spa return (also 2 inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs, it sounds as if there
are bubbles in the intake line. NOT the pump itself, but the intake
line leading to it. I don't see any air in the pump or lines. When I
close off 1/2 of thr output by closing down the pool return, leaving
only the spa line open, the presssure in the filter line jumps from
15
psi to 22 psi and the noise in the intake instantly stops. Open the
pool return line again, and the noise instantly returns. Is this
cavitation? The motor seems to run hot, but has had no problem
putting
out flow or tripping breakers. What can I do? I can't reasonably
change the intake to 2 inch without spending big $$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never seen cavitation before
,
and know little, but it sure seems like it to me.

SW,

Sounds good to me. Re-doing the piping is a good idea anyway, because that
reduction will always cause any pump to work harder.

Good luck.

Tom L.L.
"SW" wrote in message
...
I agree. So, initially when the pool guys told me to get a 1 to 1 1/2
hp pump in order to circulate 70 gpm to filter my pool once every 8
hours (32,000 gal), I did just that. My problem was that I had a Full
rated 1.5 hp super II (the same motor as a 2 hp max rated), which put
out more flow than a 2.5 hp standard Super I pump--about 130 gpm at 40
ft of head!!! Way too much.

Today I went out and got a 3/4 hp FULL RATED (service factor 1.5)
super II pump.The motor is actually a 1 1/8 hp MAX rated motor for
comparison purposes. The super II pump itself, puts out 20% more than
a standard pump. A standard 1 1/2 hp max rated pump (service factor 1)
puts out 80 gpm at 40 ft of head, 67 gpm at 50 ft of head, and 50 gpm
at 60 ft of head. The 3/4 hp full rated high efficiency super II puts
out 78 gpm at 40 ft of head, 67 at 50 ft and 56 at 60 ft. Amazing that
the lower rated pump (horsepower wise) puts out the same flow as the 1
1/2 hp max rated pump, but it does. So I needed either a 1.5 hp
standard pump or the 3/4 hp full rated super II. I bought the later
because of it's 2 inch ports and higher energy efficiency.

Anyway,I am going to change the pipe to 2 inch where it was necked
down, and enjoy energy savings while not worrying about cavitation and
damaging my filters and lines. Ahh, but what about the spa jets? Will
I have enough oomph from that 3/4 hp pump to run the 6 jets? Maybe
not, but if that's the case, I'm merely going to put a valve in to use
my Polaris booster pump double duty. When I'm in the spa, I'll divert
the 3/4 hp polaris booster to the spa instead of the cleaner.

What do you think, will this work?

Steve

On Thu, 8 May 2003 16:49:56 -0500, "Tom L. La Bron"
wrote:

SW,

The pump impeller is probably cavitating as you
suspected, which means that the flow is restricted
enough from going from two inch piping to 1 1/2
piping and so is pulling a vacuum on the water and
beating the subsequent bubble that is created
making the noise. This is pretty much confirmed
since the sound goes away when you shut down the
discharge of the pump decreasing the flow
requiring the pump to push less through the lines
meeting the flow requirement for the 1 1/2 inch
lines.

In this instance you have two choices, either
replace the piping to the pump increasing the
diameter to 2 inches for all of your piping or buy
a new pump with less discharge capacity. I guess
there is a third choice and that is leave the
discharge shut down to the point where the noise
stops.

The thing that you have to remember, if the
cavitation is allowed to continue (I do not know
what kind of pump you have) there is a chance that
the cavitation will damage you impeller requiring
pump replacement or impeller replacement.

HTH

Tom L.L.
=============================
"SW" wrote in
message
news
I have an inground pool. 2 inch plumbing
throughout, except necked
down to 1 1/2 right before the intake to the
pump. The output goes
through a filter system which has pressure
gauges and then to the pool
return line (2 inch) and the spa return (also 2
inch). The pump is
putting out 1 1/2 to 2 hp. When the pump runs,
it sounds as if there
are bubbles in the intake line. NOT the pump
itself, but the intake
line leading to it. I don't see any air in the
pump or lines. When I
close off 1/2 of thr output by closing down the
pool return, leaving
only the spa line open, the presssure in the
filter line jumps from 15
psi to 22 psi and the noise in the intake
instantly stops. Open the
pool return line again, and the noise instantly
returns. Is this
cavitation? The motor seems to run hot, but has
had no problem putting
out flow or tripping breakers. What can I do? I
can't reasonably
change the intake to 2 inch without spending big
$$ as all the valves
will need to be changed.

Is this cavitation or an air leak. I've never
seen cavitation before ,
and know little, but it sure seems like it to
me.