Totally Stopping Pump Flow, Bad?

[codee]

If I am running fresh saltwater from my mixing station up to my tank (an external Iwaki MD-70RLT is the pump) - it's a good 25 feet and down a set of stairs away from the DT - and I need to stop the flow for some reason (maybe the tank is full, or the phone rings, whatever), is it bad or damaging to the pump to totally block the flow? In other words, if I close a valve at the end of my hose, and the pump is still running full bore, will this burn out the pump because it can't push any water?

How do others solve this? Some sort of remote controlled outlet, perhaps?

 

[lpsouth1978]

I would err on the side of caution. I use Wifi outlets and can control them from my phone, or using Alexa or Google assistant. For instance, when it is time to do a water change I simply say "Ok Google, turn off return pump and skimmer" and both are turned off and I can change the water without issue. In your case, I would plug your pump into something like this and just tell it to turn off, or on, when needed.

These are the Wifi Outlets I use.

 

[BlennyTime]

WiFi outlet would be good.

It probably won’t burn the pump out if you block it occasionally for short periods of time, but the risk is that pressure builds somewhere and causes failure that results in a leak.

 

[codee]

Great, I'll check out the outlets - and I hadn't thought about the pressure issue - you're right, that could be quite a bit of stress on my fittings in my mixing station.

 

[slojim]

it won't hurt the motor. It might result in cavitation in the pump, which over time will wear the impeller. I think that pump has a seal, and that's the most likely thing to fail in this situation. So for a short time, probably ok. For the situation you describe, a wifi outlet could be the most practical solution. Some folks might run a recycle so flow is kept up, but that doesn't seem as practical in this case.

 

[codee]

it won't hurt the motor. It might result in cavitation in the pump, which over time will wear the impeller. I think that pump has a seal, and that's the most likely thing to fail in this situation. So for a short time, probably ok. For the situation you describe, a wifi outlet could be the most practical solution. Some folks might run a recycle so flow is kept up, but that doesn't seem as practical in this case.

@slojim How would I run a recycle? Interesting idea to send the water back into the mixing tank if it's blocked... is there a valve that would automatically do that?

 

[slojim]

no - you need either a short run of pipe from the pump discharge back to the suction to maintain a low flow at all times - but this will rob from your flow, or you need to carry a second hose with you and instead of shutting the flow off, you just open the vale to the second line that runs back to the source. Good solution in some circumstances, but for you, I'd stick with a smart outlet.

 

[Reefer Reboot]

Technically, what happens when you close (turn off) the discharge port of a centrifugal pump is that the water that is inside the pump is now trapped there and it just spins around with the impeller (thus no cavitation). Because of this the pump is no longer moving any water through it which actually makes it "work" less, thus drawing less amperage. The flip side of this is that the water inside the pump gradually heats up due to friction. If it were to heat up enough to the point of boiling, it could "flash" and do some damage. In high pressure hydraulic pumps (like 5,000 psi) this could happen relatively fast, but in our case of low pressure water pumps (21.33 psi in your case) it would take a long time (if ever) to get there. So, other than any potential leaks up stream of (before) the shut off valve, a minute or two won't hurt it. I do this to the transfer pump of my RODI storage tanks all the time. (Your pump is also a mag-drive so no direct mechanical drive connection to the motor.)
After all that, WIFI switches are great!

 

[Oregon Grown Reef]

Wifi outlets are awesome! I cleaned up some of the wiring for one of my systems and got the wifi outlets. It's so much nicer to tell Alexa to turn something off/on instead of trying to mess cords, often with wet hands.

I got these ones from Amazon. Super cheap. It's a surge protector, not just a power strip. 4 wifi outlets, 4 always on outlets, and 4 Smart USB outlets. Ahrise Smart Surge Protector

 

[Uncle99]

I would not put any restriction on my pump.

 

[codee]

Technically, what happens when you close (turn off) the discharge port of a centrifugal pump is that the water that is inside the pump is now trapped there and it just spins around with the impeller (thus no cavitation). Because of this the pump is no longer moving any water through it which actually makes it "work" less, thus drawing less amperage. The flip side of this is that the water inside the pump gradually heats up due to friction. If it were to heat up enough to the point of boiling, it could "flash" and do some damage. In high pressure hydraulic pumps (like 5,000 psi) this could happen relatively fast, but in our case of low pressure water pumps (21.33 psi in your case) it would take a long time (if ever) to get there. So, other than any potential leaks up stream of (before) the shut off valve, a minute or two won't hurt it. I do this to the transfer pump of my RODI storage tanks all the time. (Your pump is also a mag-drive so no direct mechanical drive connection to the motor.)
After all that, WIFI switches are great!

Appreciate the technical explanation, exactly what I was looking to learn!

 

[zalick]

Technically, what happens when you close (turn off) the discharge port of a centrifugal pump is that the water that is inside the pump is now trapped there and it just spins around with the impeller (thus no cavitation). Because of this the pump is no longer moving any water through it which actually makes it "work" less, thus drawing less amperage. The flip side of this is that the water inside the pump gradually heats up due to friction. If it were to heat up enough to the point of boiling, it could "flash" and do some damage. In high pressure hydraulic pumps (like 5,000 psi) this could happen relatively fast, but in our case of low pressure water pumps (21.33 psi in your case) it would take a long time (if ever) to get there. So, other than any potential leaks up stream of (before) the shut off valve, a minute or two won't hurt it. I do this to the transfer pump of my RODI storage tanks all the time. (Your pump is also a mag-drive so no direct mechanical drive connection to the motor.)
After all that, WIFI switches are great!

Exactly this.

I do it all the time and have a 50ft run from garage to tank. Been doing it for years. Love my Iwaki.

 

[eggplantparrot]

if you have a long run of piping then consider closing the valve slowly. if you just crank that sucker closed fast then all that water that was rushing to the valve will try to decelerate instantly, causing a giant spike of pressure, and possibly popping a seal.