Variable Flow Pumps - Recommendations?

[Cedric-Percival]

Are there any pumps available in the UK suitable for smaller ( around 3000 litre) ponds which have flow controls?

I'm hoping that having the facility to alter the rate of flow will enable me to fine tune an upcoming DIY upflow bog filter system. The bog filter tank will be 650 litres and I'm aiming to keep flow within it turning over, so to speak, every 10-15 minutes.

Many thanks in advance for your thoughts!

 

[brokensword]

Are there any pumps available in the UK suitable for smaller ( around 3000 litre) ponds which have flow controls?

I'm hoping that having the facility to alter the rate of flow will enable me to fine tune an upcoming DIY upflow bog filter system. The bog filter tank will be 650 litres and I'm aiming to keep flow within it turning over, so to speak, every 10-15 minutes.

Many thanks in advance for your thoughts!

we've had reports of those vari-speed pumps getting stuck (over time) on one speed ( @Lisak1 ), so be aware. Were it mine, I'd get either two pumps, one for each feed, or take one that is over-specced and put a wye + a ball valve on each line, then you can fine tune as you wish while not throttling the pump. And, here's another 'pro' tip (told to me by a pro, so, a pro tip!); put an adaptor on the outlet of your chosen pump that is twice (or at least 50%) larger, then add a wye, then downsize back to the original size on EACH new lead. What this does is give you max efficiency of the pump, i.e. you get full power out of your pump. Specs are like guidelines in this department. In my case, I had 1-1/2" out, so I put a 3" adaptor, then a 3" wye, then two reducers back to 1-1/2". Another good idea if you go this route; after the reducers, put a union on each so you can easily disconnect your pump from the leads. Comes in handy when you have to pull the pump with such an 'octopus' of piping right near the outlet.

 

[combatwombat]

If you can't find a variable speed pump you like, do what @brokensword said and split the output of a larger pump. Dial in the flow you want to the bog, and dump the rest somewhere else.

@brokensword: I've seen you mention this tip about upsizing your fittings a few times and finally got curious enough to look up what the actual effect would be.

In your case, the branch side of a tee fitting (don't have charts for wye) on a 1.5" line would add the equivalent of 8 feet of straight pipe and a 3" tee fitting adds the equivalent of 16 feet of pipe.

If you're running 3600 gph to each branch circuit of your pump (max I could find listed for friction loss on 1.5" pipe), you would be adding 2' of dynamic head for every 10' of piping @ 1.5" and 0.1' per 10' of piping @ 3". Therefore, you would be achieve a maximum benefit (ignoring losses from the reducer fittings) of 1.6' - 0.16 = 1.44 feet of dynamic head reduction.

Not calling that good or bad, just bored tonight and wanted to do the math.

 

[Lisak1]

We do have a variable speed pump - love the versatility, do not love the unreliability of the controls. The first one we had was wired into the control pad, so once that stopped working there was no fixing it. Pump still worked, just couldn't turn it up or down. Our newer one is plugged into the control pad, so in theory we could just replace the controls. So far it's working - fingers crossed!

 

[brokensword]

If you can't find a variable speed pump you like, do what @brokensword said and split the output of a larger pump. Dial in the flow you want to the bog, and dump the rest somewhere else.

@brokensword: I've seen you mention this tip about upsizing your fittings a few times and finally got curious enough to look up what the actual effect would be.

In your case, the branch side of a tee fitting (don't have charts for wye) on a 1.5" line would add the equivalent of 8 feet of straight pipe and a 3" tee fitting adds the equivalent of 16 feet of pipe.

If you're running 3600 gph to each branch circuit of your pump (max I could find listed for friction loss on 1.5" pipe), you would be adding 2' of dynamic head for every 10' of piping @ 1.5" and 0.1' per 10' of piping @ 3". Therefore, you would be achieve a maximum benefit (ignoring losses from the reducer fittings) of 1.6' - 0.16 = 1.44 feet of dynamic head reduction.

Not calling that good or bad, just bored tonight and wanted to do the math.

I never did the math as I wasn't trying to fix anything/spec anything at the time. I had other issues and this guy just noted that upgrade would give my pump max output, like they're low-balling the potential in the spec and the adaptor increase allows it to happen. I questioned it (still do, but hey, it works!) because the outlet is STILL the smaller size; how could I gain better function by increasing AFTER the outlet? I guess it's something to do with the friction etc. Still not sure but if it means I get more flow through 2 lines than the one, all the better. (I'm assuming this pro is referring to if I put a tee/wye at my output, that THAT flow is a lot less to each than the one I outlined above. Something like that.

Btw, what I ended up doing was from the outlet, 1-1/2 to a 3" adaptor. Then a straight, small piece of 3", then a reducing wye (3" one end, 1-1/2 on the wye side) then I reduced the 3" to 1-1/2, where I then added the union. So, if you're still bored and want to do THAT math, it could be interesting (your analysis, too), and maybe I'll understand why this is working.