Which submersible pump can you recommend for a cistern?

Hello everyone,

we have buried a 5000L cistern (flat tank) underground. The inlet and outlet (water) are connected. Also, a power cable and an HDPE (20mm) pipe are ready at the cistern. The HDPE pipe was laid from the cistern to the bed, as that is where the water is needed most.

Now I am thinking about what kind of submersible pump I should use. I am also considering whether to possibly use a Gardena spray hose to water the greenhouse at certain times or by pressing a button.

1. Could you recommend a specific submersible pump that could remain permanently in the water of the cistern? Even in winter. In my initial searches on Google, I came across the Gardena Comfort 6000/5 and Gardena Classic 5500/3.

2. How are submersible pumps generally designed? Are they only powered through a switch when the pump is needed, or is there generally a different approach?

Best regards

Unfortunately, I can't tell you anything about the pumps because our cistern was installed for different reasons and simple sewage pumps are used.

Furthermore, no flat tank was buried here. Since I read during the planning stage that flat tanks should be emptied in winter because there is a risk that the water inside them will freeze otherwise. Since these tanks are not buried as deep as the others, it would also make sense to remove the pump.

As I said, I read this somewhere.

Thank you. Unfortunately, the tank is already buried. The height of the tank is about 95 cm. The top edge is approximately 30 cm below the ground. According to the manufacturer, the water does not need to be drained. Apparently, such a large quantity should not freeze. (Standort BW, ca. 450 m ü. NHN)

You had already mentioned that the tank is already installed.

That the manufacturer says the amount of water does not freeze may be true, but I wouldn’t rely on that too much since you never know how a winter will be.

Maybe it would be possible to get a thermometer with a wired external sensor and then put the sensor into the cistern water. Then you can see how cold the water gets and react if necessary.

As I already wrote, I can’t really say much about pumps for cisterns.

But maybe the following. Our deep well pump fills a pressure tank on which a pressure switch is mounted that ultimately turns the pump on or off at a certain pressure.

And the one you first mentioned in your initial post is one that switches on when water is drawn. And when the tap is closed again, it switches off. So in principle, that would probably be the more appropriate one.
Because the second one runs as long as it is plugged in or until the float switch turns it off because there is too little water in the cistern.

Whether such a pump can handle a spray hose, however, would have to be tested. A drip hose would certainly not be ideal. I fear that the pump would constantly turn on and off. But this can also happen with a spray hose, sprinkler, or whatever they are called these days. At least that is my assumption.

One more thing: this pump has a non-return valve. That means water remains in the line. This is certainly not so good in frost, so the pump probably needs to be removed in autumn.

Oops, got a bit too much text.

Hello gardening friend, I wanted to thank you once again. The tips are already helping me or providing valuable suggestions :-)

You're welcome.
One is happy to help.
Wishing you a happy new year.