I believe I may have a problem with my system here. Now that the water
table is receding thew pump has difficulty in producing enough flow to make
the pop-ups pop.
A friend peered in to the depths of my bore liner and was able to tell me
that the inlet to the pump was far smaller than the delivery pipe to the
system. This he claimed would cause a vast reduction in the back pressure.
I would like to see the science of all this and hope that someone can point
me in the right direction.
I did not want to call in a contractor because that will cost me heaps of
dollars.
Is there a simple answer to all this?
Please, save the humour for someone else!

Don

g'day don,

is it a submersable pump or above ground pump?

i am no expert but just some things i have been told at times:

if it is above ground then the bigger the pipe coming into the pump
tghe better 2" is usually used. this reduces friction and drag. it is
also better for the pump if you have 2" going out as well for the same
reasons.

also do you have a non-return valve fitted on the outlet side this
could help in keeping initial pressure in the line.

that's my thoughts

len

snipped
--
happy gardening
'it works for me it could work for you,'

"in the end ya' gotta do what ya' gotta do" but consider others and the environment
http://hub.dataline.net.au/~gardnlen/

"Donald R Smith" wrote in message
...
I believe I may have a problem with my system here. Now that the water
table is receding thew pump has difficulty in producing enough flow to make
the pop-ups pop.

Probably due to the suction head increasing therefore getting close to the
maximum head rating of the pump.

A friend peered in to the depths of my bore liner and was able to tell me
that the inlet to the pump was far smaller than the delivery pipe to the
system. This he claimed would cause a vast reduction in the back pressure.

Changing the suction line probably wouldn't improve things as you would still be
trying to lift the same head of water.
Unless it is too small which would increase the restriction to flow, this would
cause cavitation (read footnote) to the pump and eventually destroy it.
If it has been ok in the past, I wouldn't be too concerned. Look at other
things first.

Actually, a larger delivery line is better, giving less restriction to flow you
would get increased flow to the take off points for the pop ups and better back
pressure.

I would like to see the science of all this and hope that someone can point
me in the right direction.

Do you have one line and a foot valve down the bore?

Or do you have a jet pump at the bottom (2 lines going down the bore, 2
different sizes) for self priming.

I did not want to call in a contractor because that will cost me heaps of
dollars.
Is there a simple answer to all this?

Honestly, there is no simple answer, But, because the water level has dropped,
the ability for the pump to lift (actually, the ability for the pump to create
enough vacuum to allow the air pressure (atmospheric pressure) to push the water
up the line and into the pump) has reduced.

Maybe a larger capacity pump might be the answer.

Do you know the distance from the pump to the water level (Not the length of the
suction line, which would be longer), compare that with the rating of the
pump.....

Oh, Another thing, what is the condition of the pump inside, any sign of
cavitation, are the impellers ok, is there a buildup of any rust, calcium, etc
inside the pump. If the fittings are galvanised fittings there may be a buildup
inside the fittings reducing the capacity of the pump

Good luck!
Gerard


Footnote:
Cavitation is the formation of vapour bubbles within a liquid at low-pressure
regions that occur in places where the liquid has been accelerated to high
velocities, as in the operation of centrifugal pumps, water turbines, and marine
propellers. Cavitation is undesirable because it produces extensive erosion of
the rotating blades, additional noise from the resultant knocking and
vibrations, and a significant reduction of efficiency because it distorts the
flow pattern. The cavities form when the pressure of the liquid has been reduced
to its vapour pressure; they expand as the pressure is further reduced along
with the flow and suddenly collapse when they reach regions of higher pressure.
The sudden growth and collapse of these vapour cavities cause the extreme
pressures that pit the metal surfaces exposed to the cavitating liquid.

"len brauer" wrote in message
...
g'day don,

is it a submersable pump or above ground pump?

i am no expert but just some things i have been told at times:

if it is above ground then the bigger the pipe coming into the pump
tghe better 2" is usually used. this reduces friction and drag. it is
also better for the pump if you have 2" going out as well for the same
reasons.

also do you have a non-return valve fitted on the outlet side this
could help in keeping initial pressure in the line.


I agree with all but the non-return valve, this must be placed at the bottom of
the suction line, normally refered as the foot valve, although both valves
(foot, non-return/check) are identical in principle, inline valves are usually
refered to as check or non-return valves and are usually spring assisted, but
the foot valve as stated previously is placed at the foot of a suction line and
is not spring assisted, only by gravity and the head of the fluid.

Regards
Gerard

Arvo All,
Two major leaks have been detected.
One at a joint in the 2" main at the rear of the house. The main is 500mms
down and would have made the leak difficult to detect.
The other was in the front yard at a crossover where the 1 1/4" main fed two
1" feeds to a sprinkler line either side. When originally installed, a
Conifer was planted immediately above it shortly afterwards. Eight months
ago I removed the 40 foot tree and digging through a maze of roots, found
that the original crossover joint was covered by the old stump and only just
visible. It was impossible to get at but was the source of another major
leak.
Now the main has been re-fed and is on top of the old stump (not pretty) but
the only way it could be achieved without a heck of a lot of work and
creating two new feeds.
My retic man then showed me just how much water was leaking up the side of
the pop-ups. Now they have all been replaced and everything seems to be
jake.
I fell base over apex by putting my foot into one of the bomb craters I had
to dig all around the front yard.
Today I'm resting.
There is a two inch GI pipe down the hole and a flange or something which
stops a string being lowered any further. Opinion has it that the
obstruction is the top of the spear/non-return valve. No wiser! The
neighbour whose bore is right over the fence from mine tells me the water is
down to 12 1/2 feet at the moment.
Thanks for all of the help and advice.

Cheers,
Don