Rain water harvesting first flush diverter

I've never understood the function of the floating ball in a first flush diverter. The instructions say it seals off the diverter after the first fill, but I can't see how the physics of that works. There is no negative vacuum formed to keep it sucked up into the seat so it will just drop as the flush chamber empties and the chamber will be topped up at the rate it drains from the outlet.

On the other hand if the diverted water is emptying fast enough the ball will more likely be sucked down onto the outlet hole and seal against that.

Is there actually any real point in putting a ball in a FF diverter? Maybe it limits a bit of turbulence in the water stream but what else does it achieve?

There is a restricted drain on the vertical tube, this empties at a much slower rate than the water influx so the ball floats to the top and remains there until the rain event is over. As to what else it achieves, it blocks buoyant detritus from floating into the main stream of water and washing to the tank.

The ball does nothing to control the rate of emptying of the chamber. The flow of water past the t junction will be no different with or without the ball. I can sort of see how if there was large bits of floaties it might make a difference but small bits, not so much.

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Originally Posted by Fuzzie

The ball does nothing to control the rate of emptying of the chamber. The flow of water past the t junction will be no different with or without the ball. I can sort of see how if there was large bits of floaties it might make a difference but small bits, not so much.

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The rate of emptying is controlled by the drain at the bottom yes. The divert chamber is initially empty, the crap gets flushed in, sits on the surface of the water column and would flush out of the first flush reservoir but the ball gets there first and seals the opening. I'm fairly certain that this would have been tested and companies maximising profits wouldn't put superfluous material into it.

The tanks top inlet mesh screen seems to be fine enough to catch the worst of the floaty bits and if it gets into the tank it will eventually flush out the overflow outlet anyway. The first flush diverter seems to be more targeted at catching the first flush of dirt and dissolved crap like bird droppings.

On a previous tank I had the dirt/mud/sludge was always thick enough to clog all the sizes of outlet restrictor washers supplied and when I eventually took those out off the system, the fine filter and basket before the restrictor were always getting clogged anyway. They had to come out too. Airborne dust and dirty rain seem to have always been my biggest problem