"Jeff Lowe" wrote in message
...
snip
Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the
input
or output.
snip

I have often wondered about that and assumed that by restricting the input
the pump would be able to empty the chamber faster then it could fill it
causes the chamber to be a mix of air and water, whereas if you restrict the
output, the chamber will retain more water and less air. Surely both ways
make the pump work a bit harder, but it seems to be restricting the output
is better for it then restricting the input.

BV.

In uk.d-i-y Jeff Lowe wrote:

"Tim Downie" wrote in message
...
Gale Pearce wrote:
You can restrict the outflow side of the pump, but not the intake or
you will burn out your pump prematurely - I use a "ball valve" to
reduce the waterflow on my submersible pump on the line to my filter
Gale :~)

I've already got a restrictor and T-piece on the pump outlet so I can
control the output at present. Somehow it doesn't feel "right" to reduce
the flow this way. I can't help feeling that it's putting extra load on
the
pump. As I have a reasonably hefty lamp dimmer kicking around, I was
just
wondering if using a device like this would be more mechanically
"sympathetic" IYKWIM. (Probably complete nonsense I know).

Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the input
or output. I would not use a lamp dimmer since these are typically just

Cavitation is a real concern if you put it on the input.
This does cause RAPID wear on the impeller.

It is generally best never to restrict the input of a pump. I did not get to
see the original pump type, but many explicitly spell that out in their
directions as it does for my Sequence pump. Try to "reuse" the pump pressure
in other ways - redirect part to a filter/waterfall. Restricting the pump on
the output side is the same as adding head pressure due to vertical pump
height, fitting losses, change in pipe diameter etc... All reduce flow
rates.
Tim

"Benign Vanilla" wrote in message
...

"Jeff Lowe" wrote in message
...
snip
Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the
input
or output.
snip

I have often wondered about that and assumed that by restricting the input
the pump would be able to empty the chamber faster then it could fill it
causes the chamber to be a mix of air and water, whereas if you restrict
the
output, the chamber will retain more water and less air. Surely both ways
make the pump work a bit harder, but it seems to be restricting the output
is better for it then restricting the input.

BV.

"Ian Stirling" wrote in message
...
In uk.d-i-y Jeff Lowe wrote:

"Tim Downie" wrote in message
...
Gale Pearce wrote:
You can restrict the outflow side of the pump, but not the intake or
you will burn out your pump prematurely - I use a "ball valve" to
reduce the waterflow on my submersible pump on the line to my filter
Gale :~)

I've already got a restrictor and T-piece on the pump outlet so I can
control the output at present. Somehow it doesn't feel "right" to
reduce
the flow this way. I can't help feeling that it's putting extra load
on
the
pump. As I have a reasonably hefty lamp dimmer kicking around, I was
just
wondering if using a device like this would be more mechanically
"sympathetic" IYKWIM. (Probably complete nonsense I know).

Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the
input
or output. I would not use a lamp dimmer since these are typically just

Cavitation is a real concern if you put it on the input.
This does cause RAPID wear on the impeller.

Since we were talking about lamp dimmers I guess I assumed we were talking
fractional horsepower. I didn't think these capable of enough suction get
below water's vapor pressure at pond temperature. I mean that's 29" Hg. Of
course some ponds and pumps are bigger than others ;-)

Jeff

In uk.d-i-y Jeff Lowe wrote:
"Ian Stirling" wrote in message
...
In uk.d-i-y Jeff Lowe wrote:

"Tim Downie" wrote in message
...
Gale Pearce wrote:
You can restrict the outflow side of the pump, but not the intake or
you will burn out your pump prematurely - I use a "ball valve" to
reduce the waterflow on my submersible pump on the line to my filter
Gale :~)

I've already got a restrictor and T-piece on the pump outlet so I can
control the output at present. Somehow it doesn't feel "right" to
reduce
the flow this way. I can't help feeling that it's putting extra load
on
the
pump. As I have a reasonably hefty lamp dimmer kicking around, I was
just
wondering if using a device like this would be more mechanically
"sympathetic" IYKWIM. (Probably complete nonsense I know).

Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the
input
or output. I would not use a lamp dimmer since these are typically just

Cavitation is a real concern if you put it on the input.
This does cause RAPID wear on the impeller.

Since we were talking about lamp dimmers I guess I assumed we were talking
fractional horsepower. I didn't think these capable of enough suction get
below water's vapor pressure at pond temperature. I mean that's 29" Hg. Of
course some ponds and pumps are bigger than others ;-)

That's not quite how it works.
The large amount of turbulence in the pump means that the pressure
varies quite a lot.
It's quite easy to get pressure locally to fall down below the vapour
pressure.
Then the bubbles collapse, and the rebound is VERY powerful.
This happens even to speedboat propellers ofr example.

"Geoff Beale" wrote in message
...


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Rather than waste the pump's output by restricting it, run a "T" off the
output side and divert some of the flow to a home-made venturi (another
"T" with a restrictor on the long side and and an air intake tube into
the short side - you have to experiment a bit to get it right). This
will add valuable oxygenation to your pond and add a little more
movement to the water. Balance the flow between the two outputs with
ball valves on the hoses.



Nice idea, but I doubt he needs anymore oxygen being added to the pond if
there is a a reasonable amount of water movement at the surface. Indeed too
much disolved O2 is bad, as it reduces the waters ability to carry CO2 which
is needed for plant life. Often putting too much O2 in will simply cause
algee to thrive.

Scott

Scott Mills wrote:
Nice idea, but I doubt he needs anymore oxygen being added to the
pond if there is a a reasonable amount of water movement at the
surface. Indeed too much disolved O2 is bad, as it reduces the waters
ability to carry CO2 which is needed for plant life. Often putting
too much O2 in will simply cause algee to thrive.

Scott

The jet from a venturi is said to stabilize the level of oxygen and
prevent over-oxygenation. Adequate planting is the key to algae
control.
--
Geoff Beale
Extract digit to email.

Nice idea, but I doubt he needs anymore oxygen being added to the pond if
there is a a reasonable amount of water movement at the surface. Indeed too
much disolved O2 is bad, as it reduces the waters ability to carry CO2 which
is needed for plant life.

The way I remember it is that surface agitation enables CO2 to reach
equilibrium with the atmosphere which is a low value. Without agitation it
tends to supersaturate (assuming CO2 producers like fish) which is better for
submersed plants, not a factor for plants with leaves in the air.

"Ian Stirling" wrote in message
...

In this case, simple speed controllers won't actually work, it'll stay at
a constant speed (3000RPM) until it stops working, and hums loudly.
Suitable speed controllers are going for around 40-50 quid on ebay.
Search on
inverter phase motor induction
on ebay, searching titles and descriptions.

Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
just had to try it. The lamp dimmer, in the best traditions of DIY, was
scavenged from the next door neighbours bin. I wired it up, tested it with
a lamp and then plugged a smaller version of the same pump in to it.

As you said,initially no change and then just a sudden cessation of pumping.
Maybe a smaller pump will be the easiest option.

Cheers.

Tim

On Sat, 22 May 2004 22:51:30 +0100, "Tim Downie"
wrote:


"Ian Stirling" wrote in message
...

In this case, simple speed controllers won't actually work, it'll stay at
a constant speed (3000RPM) until it stops working, and hums loudly.
Suitable speed controllers are going for around 40-50 quid on ebay.
Search on
inverter phase motor induction
on ebay, searching titles and descriptions.

Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
just had to try it. The lamp dimmer, in the best traditions of DIY, was
scavenged from the next door neighbours bin. I wired it up, tested it with
a lamp and then plugged a smaller version of the same pump in to it.

As you said,initially no change and then just a sudden cessation of pumping.
Maybe a smaller pump will be the easiest option.

Cheers.

Tim

Lamp dimmers do ther job by chopping off the peaks of the power's sine
wave.

Run an electric motor through it and you're likely to get a fried
motor, assuming the dimmer doesn't overload and smoke first.

HTH, hope it's not too late for you. :-)
When you let the "go-smoke' out of electronics, they won't go anymore.

Mike


Mike Patterson
Please remove the spamtrap to email me.
"I always wanted to be somebody. I should have been more specific..."

On Fri, 21 May 2004 17:35:43 +0100, John Laird
wrote:

--
Too much month at the end of the money.

I couldn't have said that better.

In this case, simple speed controllers won't actually work, it'll stay at
a constant speed (3000RPM) until it stops working, and hums loudly.
Suitable speed controllers are going for around 40-50 quid on ebay.
Search on
inverter phase motor induction
on ebay, searching titles and descriptions.

Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
just had to try it. The lamp dimmer, in the best traditions of DIY, was
scavenged from the next door neighbours bin. I wired it up, tested it with
a lamp and then plugged a smaller version of the same pump in to it.

I had the opposite result. I used a fan speed control which is just a
dimmer with a snubber to protect the triac. The speed changed just fine.
This was before I purchased the Kill-a-watt meter so I didn't measure
the energy usage.