Pumps

[20x]

If I put 2 inch reducers on the inlet and outlet of a 3 inch pump, will I save fuel and require less revs than a 2 inch pump?

 

[Simmo]

I'm guessing here but wouldn't the opposite occur?
You have to draw (suction) through a smaller pipe, resulting in higher pressure, so more revs required.
Then you are delivering through a restriction so again higher pressure, so more grunt required??

I'm thinking.... IF?! you left the suction at 3" and reduced delivery to 2", then turned down the revs to get the same amount of water at the destination??
I'm only guessing though mate, I don't know the answer!!

 

[user 12139]

I'm thinking.... IF?! you left the suction at 3" and reduced delivery to 2", then turned down the revs to get the same amount of water at the destination??
I'm only guessing though mate, I don't know the answer!!

your on the money there Simmo. Its best to have the suction running as efficient as possible by minimising suction frictional pressures which in turn helps to prevent pump cavitation. Cavitation is the leading cause of premature impeller and housing wear. So as Simmo suggested stick to your 3" suction and choke back on the discharge and revs. Just keep an eye on the impeller housing temp, you dont want it getting beyond warm

 

[20x]

I agree, only thinking of this if I get a cheapy from Johnno and johnno, a 2 inch pull start with hoses and fittings 35,000 litre/hr $460.
honda gx160, 2 inch high flow 33,000 litre/hr $520 on its own But 50% better fuel economy.
Or the 3 inch thornado 60,000 litre/hr $320.

 

[Simmo]

I'm gonna be an elephant in the room here!!
What is it you want the water delivery to do??

I have many pumps, from a 6 cylinder Fordson/Southern cross through to a high head dual impeller diesel unit and the cheap chinese Chonda ones too!
Each has a specific purpose..

 

[20x]

Feed 2 x 6 inch dream matts, I haven't fed dream Matt with a pump before.
All I know from the river sluice is mini dream Matt works best around 5 % fall and HEAPS of flow..

 

[Simmo]

No probs!
I think our suggestion of keeping suction as designed, then reducing and adjust revs accordingly should work??
I am unsure of what it would save you fuel wise?

 

[20x]

The best option might be the honda 2 inch, surely 9 litres / per second flat out will be more than enough so I can back the revs off a bit..

 

[20x]

How's the little consumption equasion for the Johnno and Johnno 2 inch..

 

[meanfreddy]

If I put 2 inch reducers on the inlet and outlet of a 3 inch pump, will I save fuel and require less revs than a 2 inch pump?

I have a split pipe of my 2inch outlet pipe, if it's pumping to much presure I open the split release on the 2 inch out let pipe and gradually cut the splitter tap back until I get the right amount of pressure

 

[Grey Panner]

I have a split pipe of my 2inch outlet pipe, if it's pumping to much presure I open the split release on the 2 inch out let pipe and gradually cut the splitter tap back until I get the right amount of pressure

Hi Meanfreddy,
I suspect that requiring a 3 inch pump to draw water in through a restricted nozzle and then force it out through a restricted nozzle would require more effort and therefore use more fuel.
I think the pump's designers would have built-in the most efficient factors when designing the machine.
If it is a good pump designed by a reputable maker it probably operates at peak proficiency as is.
Nevertheless, fiddling with machines is enjoyable and for the price of a couple of adaptors you could prove me wrong,
Why not give it a burl.
Cheers, Grey Panner?

 

[gragagan]

I've found that an 1100 gph bilge pump is just about right for running a single 6 inch dream mat. Only cost about $20 on ebay, runs off 12v power, only draws 3 amps or something. But the flow from the pump to the unit needs to be smooth, ie no right angles, no changes in pipe diameter. (Back when using powered equipment was still allowed in nsw)

 

[20x]

I ended up buying the 2 inch Johnno and Johnno, ran nice actually when I tested it, started first pull, 2 x 6 inch dream Matts needs at least half throttle.

 

[ken2m]

Water friction will increase in a 2" hose compared to a 3" hose, the flow will be about twice as fast to get the same quantity of water through to the highbanker, as the area of the hose is about doubled with a 3" compared to a 2". What simmo said is spot on with the suction hose, keep it at 3" as any reduction on the intake (including restrictive foot valves) take more power than if it was restricted on the output. Also keep your intake as short as possible to reduce losses. Pipe friction is a major flow reducer, after running 250m of 1 1/2" polly tube a 35,000L/hour @125PSI pump was running at about 3,500L/hour, this is only about 10% of the delivery rate of the pump with no hose.

 

[lazypat]

If I put 2 inch reducers on the inlet and outlet of a 3 inch pump, will I save fuel and require less revs than a 2 inch pump?

on my 2inch bigger pump the pressure is to great so i put a T join in the hose with a tap on each , so to cut the pressure back i turn the side tap on which is one hose two outlets and keep opening the side tap up until it lets the correct pressure and volume into my high banker and other goes back into the creek

 

[Rusty_G]

Just a general tip, if you have 6" Dream Mat and want to run electric, 1100gph is only going to be sufficient if you screen to 1/8th". If you want to run more volume and get the mat working optimally you would do well to aim for 2000gph, this way you have some flexibility with hose length and a little room for lift.
Edit: I would think you if you get the 1100gph, you may be happy with the price and disappointed with the result and end up spending more to get it better.

(Sharing from my testing experiences).