The Nova Flo, which was featured on Dragon’s Den, is a device to stop baths overflowing onto the floor where the flow exceeds the overflow capacity, or it can simply be used to stop water being wasted.

The target market would be the young, the old , the absent minded, the blind, infirm or my wife – who is none of the above but cannot seem to let a phone go unanswered when she is busy, and is then totally absorbed by the conversation to the point where she is oblivious to the running bath or burning pan cooking.

This device solves the bath problem, now I just need to find a similar device to turn the cooker off. In the interests of balance she might say that device is sitting on the sofa watching football.

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The Nova Flo proved very easy to fit with push fits and it comes with adaptors for different sized flexible overflow pipes. It is not quite so easy to fit if you are using a rigid overflow telescopic pipe. If you are using a combined filler and waste you simply have to tee the two ports into one pipe at the top and bottom. At first I couldn’t see quite see why you can’t leave one port unused but it is a question of limiting the flow rate through the ports to prevent nuisance operation. All this became clear to me when (in the interests of research) I decided to get my screwdriver out and take the thing apart.

I discovered two magnetic float switches which raise two flaps in the hot and cold supply. Once the pressure of the water is behind the flaps they are closed until the water pressure is equalised by turning the taps off. This is the clever bit. The flaps let by so a little water keeps trickling out of the taps. This reminds the user (returning from that all absorbing phone call) to turn the taps off.
So even when the float switches drop, the flaps remain closed(ish) to prevent a further operation sequence. If the flap valves didn’t have holes in them they would remain closed by the pressure even when the taps were off but those holes work like an equilibrium valve allow them to drop gently back down in around 5 seconds. After this the taps can be turned on again and the full flow is returned.
Obviously there is a risk that those flap valves can be activated by exceptionally high flow rates, so you might need to throttle the supply on a couple of Ballofixes. There is also a maximum temperature rating of 60°C, so in cases where this might be substantially exceeded you should fit a thermostatic blending valve. In case you are wondering about potential leaks, there is no physical link between the supply pipes and the overflow. The mechanics are simple magnetic switches activated by the float so the supply is not breached by mechanical devices.

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