Pump pitfalls

The self-seeded pumpkins have taken over the front raingarden. The grapevine’s leaves are turning brown and slowly shedding in the back. The raingardens’ productive summer ends with us in lockdown, giving me time to reflect on the raingarden news I have let slip over the last year.

A year ago, Maree and I were in Spain on a 5-month cycling holiday (magnificent, thanks for asking). We had left the house and its stormwater management system in charge of the two girls, whose care factor for the system was low-to-moderate. It was a good test for the resilience of the system when its residents were less obsessive than I. Pleasingly, it all worked well; they embraced using the veggies and only needed to turn the pump on once.

The pump: a Vada V80-H. Coming up for 6-years old and it is still working without a hitch. However, the rain-to-main switch on top of the pump has never worked as I expected to (well, at all, really). Every time the tank has emptied, I have had to manually turn the pump off, and every time it has filled above the pump intake, I have had to manually turn the pump back on. Fortunately, this only happens once or twice a year, so it had never been a major annoyance, and I let it go.

But with us heading off for 5 months, and leaving it to the girls, I decided to have a closer look into why it wasn’t working.

When the tank empties to the level of the pump intake, the pump starts being noisy, taking in air as well water. A few times, we let it keep being noisy, taking an increasingly long time to fill the toilet cistern, until water flow was negligible. At no point, was there a hint of the ‘rain-to-main’ switching to the mains as expected.

On the advice of Rob, our resident sparky at work, I tested if it switched to mains if water supply from the tank was cut off completely (by turning off the inlet tap into the pump). And what do you know? It worked. The switch was working to its specification, but the gradual draw down of water from the tank, slowly reducing the inflow into the pump was too gradual to trip the switch.

Now, I might have put in the effort to think through a way to make it work better. But the exercise had spurred me to read the Rain-to-main’s specifications more carefully. Much to my surprise, it is designed only to do as it suggests: switch from rainwater to mains. It is not designed to switch back automatically, when the tank refills.

I figured, that if I had to manually switch it back to rainwater, I might as well continue to put up with having to switch it to mains when it empties. The tank was empty when we left on our holiday last year, and the girls were happy enough to switch it back to rainwater when it rained a week later, and fortunately it didn’t empty again while we were away.

So, the upshot is that Vada’s Rain-to-main switch does not work on systems like ours with a gradual reduction of inflow to the pump, and it isn’t designed to do what I thought it was going to do (switch back and forth between tank water and mains water as the tank fills and empties). I’m going to continue to put up with it as it is until the pump dies (hopefully no time soon). When it does, I’ll investigate (with the help of smart colleagues) a switch that will do what we need.

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