Pump redundancy - backup

[Gorgok]

Can't really do anything about outlet or after pump issues without separate plumbing.

Simplest way to have a backup without separate plumbing is to series the pumps. Then you still do have the risk of intake clogging though. A dead pump after the functioning one will slow flow some, but not so much i would worry about it.

Or you could manifold the pumps in parallel with a diverter valve, then you have individual intakes while still sharing the outlet plumbing. Like this: Pentair diverter

With series pumps i'd just run them all on, if some fails then flow just slows. With parallel you might have to check how much practical flow loss comes from them fighting each other and decide if running both is a waste or not. But running one, flipping the diverter, then running the other is an option. With non-running pumps exposed to the tank you always have the added risk of it fouling from growth and not being a backup when needed though.

 

[karimwassef]

I like the idea of series pumps because it's passive redundancy. There's no action needed to make sure the system is on. I can even have one running on the UPS just in case.

If one fails, the flow won't drop much - just the pressure will drop a lot and that will impact flow somewhat. It's not half the flow. It's not 100% of flow. Something in the middle closer to 100%. Without running the math, I'll call it 85%.

The only drawback is the power wasted for no real benefit under normal operation. Sure, the pressure will go up, but that's not of much value for a circulating pump unless I add penductors at the end to convert the pressure into more in-tank flow. And even then, it doesn't increase the flow through the sump...

Hmmm.
I like it because I don't have to do anything in case of a failure.
I don't like it because I pay for running it without benefit most of the time...

 

[Gorgok]

If you got clever with controls you could probably run the two pumps at a reduced level, like 60% each while everything is fine, and then if one fails set the remaining one to 100% on the control. It should help offset the wasted power. With some live testing it could even be set to effectively be the same flow in both cases.

But really at 100W is the additional energy use really meaningful? With 2+kW of stuff in the tank already...

 

[karimwassef]

It's a 200W pump, and those little watts add up- just like cents...

Aside from my cheap self, the attraction to the series configuration is that it's passive redundancy. No controls needed.

I think I just have to find a creative way to use the pressure.