Can an aquarium water pump been damaged by being made to work slow

[Birrofilo]

I am building a reflux CM still.
We know precision of flow in the dephlegmator of a CM still is important.
In order to stabilize the water flow on the dephlegmator and final condenser of the still which I am eternally trying to put into operation, I bought a water pump.
The idea is to fill a basin with water, and put the submersible pump into it. The water in the basin is kept at the brim (it overflows a bit) and the pressure over the pump is constant. The pump should pump at a regular "energy" and the flow arriving to the still should be constant. I will regulate the flow with needle valves on the still (a needle valve on the final condenser and a needle valve on the dephlegmator).

I did not want to buy a super-cheap water pump because I did not want it to break during a distilling run, stressed by hours of continuous operation (although those pumps should work continuously).

I bought this pump: https://www.amazon.it/gp/product/B07B8M ... UTF8&psc=1

It's a 40W pump with 2,8m of declared water elevation. It has no regulator.

When I manage to make the water connection properly to my "T" which splits the water (to dephlegmator, to final condenser) the pump will try to push a lot more water than the needle valve will let pass through.

I am wondering whether this operation, with the water flow "choked" by the needle valve, is stressful for the pump, especially a 40W pump. I understand many use this system, but with smaller pumps.

[NineInchNails]

The pump should be just fine. Temp should be the only issue since aquarium pumps are not intended to be operated in high temp water.

You can restrict aquarium pump's outlet, but you can damage the pump by restricting the inlet.

[The Baker]

It would be simple to adjust the flow with a bypass valve.
Now let's see....

Cut a tee into the (outlet from the pump -- inlet to the condenser, whatever) tube.
Put a tap in the new line which you will run back to the intake reservoir.
Diverting water by means of the tap will reduce and adjust flow to the condenser without retarding the flow from the pump.
Simple.
Cheap.

Geoff

[NineInchNails]

It would be simple to adjust the flow with a bypass valve.
Now let's see....

Cut a tee into the (outlet from the pump -- inlet to the condenser, whatever) tube.
Put a tap in the new line which you will run back to the intake reservoir.
Diverting water by means of the tap will reduce and adjust flow to the condenser without retarding the flow from the pump.
Simple.
Cheap.

Geoff

If I'm not mistaken, the OP splits the flow of water from his pump. One leg goes to the deflag and the other goes to the final condenser. I believe he uses 2 needle valves, one to control the flow for each condenser. If he uses a single bypass before both condensers, it may, but also may not provide enough pressure to feed each condenser adequately. If that works then it should relieve a significant amount of the back-pressure. It's worth a try.

If I'm not mistaken, I don't think it would work well to have 2 bypasses (one bypass prior to each needle valve). I mean something like that may work, but would likely require a LOT of fiddling to get it adjusted correctly.

[The Baker]

I believe a bypass "before everything" would simply reduce/ adjust the pressure in the entire "system", to a pressure that works best.

Geoff

[Birrofilo]

Thanks for your answers.

The hot water will be discarded in the sink, I will not "recycle" it. The pump is meant only for uniformity of pressure.
I will not restrict the water inflow: the pump will be submerged into a plastic basin. Actually this pump has no real "inlet" for water, it takes incoming water from the slots in its body.

I am not sure if I understood well the bypass valve trick.

If I insert a T, let's call it T1, between the pump and the T which, in turn, will split the water between dephlegmator (reflux condenser) and final condenser, which we will call T2, and one branch of T1 goes to T2, and the other branch of T1 goes back to the plastic basin, which is the place whence the pump pumps the water, what advantage do I obtain?
If the pressure goes up, the excess pressure will be applied, I imagine, on both branches of T1, so will not T2 receive an excess pressure in any case?

In my setup, the plastic basin (which has the pump inside it) it's full to the brim always, the tap fills the basin with a constant flow slightly in excess of need. The basin is in a slight constant overflow mode.
If I send the bypass water to the basin, it doesn't have any real effect, because the basin is already full to the brim - overflowing.

For what I understand, the pump in the basin will do fine. The overflowing of the basin will keep the exact same amount of water above the pump at any moment.

Maybe it's useful to explain the bypass-valve trick for a future reader.

Thanks to all
Fabrizio

[The Baker]

Dear B,

You have thoroughly overthought the whole thing and I can not explain any more simply from the place you have gotten yourself into.

Good luck anyway with everything.

Geoff

[NineInchNails]

If you have a faucet (or water source) for water and you are sending the warm water down the drain ... why don't you just run water directly to your condenser/condensers straight from the spigot and send the warm water down the drain? Use a valve to create a constant, steady flow.

The plastic basin and pump would serve no purpose at all. Some people are concerned about water consumption, use a reservoir to hold water and recirculate the water through their condenser/condensers back to the reservoir. In that case you would use a pump. Many run water from the pump, to the valve (which controls the flow) and you can always bleed off any back-pressure by installing a T with valve after the pump.

[trebor66n2]

I use an aquarium pump, I put a tee in the line to the condenser, a ball valve after the tee. All pvc. I can open or close the ball valve to control cooling water, and it takes the stress from back pressure off of pump

[Birrofilo]

If you have a faucet (or water source) for water and you are sending the warm water down the drain ... why don't you just run water directly to your condenser/condensers straight from the spigot and send the warm water down the drain? Use a valve to create a constant, steady flow.

For what I read, the pressure from the spigot is not constant.
The pump was meant to push water with a constant pressure. If the pump is immersed in a constant height of water, the entire water pressure should be constant, even if the pressure from the tap is not.
Or this is what I thought it would happen.

I am still waiting for the water connectors to assemble the entire rig.

[Birrofilo]

I use an aquarium pump, I put a tee in the line to the condenser, a ball valve after the tee. All pvc. I can open or close the ball valve to control cooling water, and it takes the stress from back pressure off of pump

I will have a needle valve at the entrance (cold water) of both condensers.
The idea is: pump -> T -> needle valve dephlegmator and T -> needle valve final condenser