Peggie,
I know that you are an expert, but I have some justification for using a switch. Mine isn't actually a night switch. As you state, a night switch is so that the VF doesn't cycle during the night. I have a "parts and maintenance reduction" switch next to my VF head.
The VF system is designed to be left on 24-7.
Maybe that is a design flaw, as 24-7 live electrical feed is not necessary for the system to fully function. It does save the installer from putting in a "parts and maintenance reduction" switch, but from the posts I've read it sounds like not having one creates more maintenance for the owner (which requires more parts.) As I'm sure you know, the switch is simply inline with the vacuum switch on the tank. It is only the cost of a switch and X feet of wire. It would cost less than a set of duckbills (and much easier and more pleasant to install.)
I've known people (me included) who've accidentally left it on at the breaker when leaving the boat and returned a week or more later to find it still holding full vacuum.
I've had a counter in the bilge pump to tell if cycles when I'm gone, but never heard of anybody with one on the VF. How would one know when returning three weeks later that it hasn't cycles once (or more)? With a parts and maintenance reduction switch, leaving the breaker on isn't an issue. I
know that mine doesn't cycle in my absence even should I leave the breaker on.
Cycling is an indication of a tiny leak caused by a crack in a seal or maybe just a particle. Having effluent constantly sucked through that leak can only worsen the situation. Maybe make the leak permanent. Most likely hasten the need for seal replacement. My reasoning is that it is better to turn off the vacuum as much as possible to save the seals.
Turning it on and off with every use just puts unnecessary wear on it on the pump and may prevent it from pushing the flush all the way to the tank.
I don't see how not running a pump causes wear. I can see how leaving it on puts wear on the system, as it may cycle in one's absence. My parts and maintenance reduction switch can only reduce the pump run time, but not increase it (or the amount of time the system is under vacuum.)
I don't think that the VF system is clairvoyant and
knows when the effluent has reached the tank. It simply turns off based on the vacuum setting. Even if the VF system were clairvoyant, one can simply wait until the system reaches the preset vacuum, turns itself off, and then throw the switch. A quick flush and the system is at zero vacuum. Won't cycle, doesn't leave tank and hoses under stress, can't have leak down eroding duckbills.
Leaving it off except to use the toilet also prevents you from hearing the pump running for no reason between flushes, which is the first indication of an air leak and may or may only let you know it's time to replace the duckbills, but can reveal an air leak somewhere else or a failing vacuum tank switch.
By using the parts and maintenance reduction switch I'm still testing the vacuum tank switch every time. I'm just not testing how many minutes, hours, days, weeks the entire system can try to hold a vacuum. Because I don't need to (and therefore I really don't care).
You don't turn of the water to a household toilet after every flush...don't turn off the night switch to a VF after every flush either!
But you could (and probably would) shut the water off every time if it was easier than routinely trouble shooting and replacing the toilet plumbing (i.e., less cost and maintenance.) Actually, changing a toilet flapper is a walk in the park compared to any VF seal/tank/hose/pump maintenance. And if turning off the water to a household toilet was as easy as pushing a simple button next to a VF head, I would guess that a switch would replace the household toilet flapper system.
Maybe I should be worried that my duckbills might not hold the proper duration, but I don't care. I don't even know how many hours/days/weeks my seals should hold a vacuum. Are there are rules of conduct or a code of behavior regarding VF vacuum retention? I'm probably a bad boater for not routinely testing the vacuum, buying VF parts, and replacing my duckbills and seals. Instead, I'm cheating with a parts and maintenance reduction switch. So far, so good.
