Vacuflush vacuum switch shutoff vacuum level?

[mobocracy]

My head system decided it was time for my annual pre-4th of July troubleshooting session by going into “pump never stops running” mode.

Last year I wised up and got a vacuum gauge but never needed to use it.

This year I figured it would be helpful and I checked the vacuum at both the inlet at the vacuum pump and at the head. I’m getting a solid 12 inches of Hg on my gauge in both places. No visible loss of vacuum on the gauge with the pump turned off.

Left for a minute or two, the head flushes real solid, too.

I suspect the vacuum shutoff switch is getting flaky. I can ever so slightly touch it and the pump shuts off and stays off.

But I can’t find a reference number for how much vacuum I should expect to see or what pressure the switch is calibrated to shut off. Does anyone know?

 

[Happy Hour IV]

I googled it for my on use and found 10 inches HG. I recently upgraded/replaced ducks, some hose, upper/lower pump body, upgraded bellows and motor. My switch went south about ten years ago during a trip, bought a wheelbarrow inner tube at the island hardware and made a new diaphragm. not bad for a couple bucks but all boat things must eventually fail including the plastic framework of the switch. broke out the big bucks for a new switch assembly. I did notice that manually pushing the switch in either direction it seems to stick, but after careful thought I realized moving the switch does not really change the pressure (vac) behind it so it is not likely to be very sensitive. I suspect this explains your experience and all is good. But write back after you use the gauge. I do not know what system you have but checking at the pump may not be accurate as there may not be a lot of air volume behind to stabilize. I think the best place would be at the head or at the inlet to the vac tank.

 

[mobocracy]

I googled it for my on use and found 10 inches HG. I recently upgraded/replaced ducks, some hose, upper/lower pump body, upgraded bellows and motor. My switch went south about ten years ago during a trip, bought a wheelbarrow inner tube at the island hardware and made a new diaphragm. not bad for a couple bucks but all boat things must eventually fail including the plastic framework of the switch. broke out the big bucks for a new switch assembly. I did notice that manually pushing the switch in either direction it seems to stick, but after careful thought I realized moving the switch does not really change the pressure (vac) behind it so it is not likely to be very sensitive. I suspect this explains your experience and all is good. But write back after you use the gauge. I do not know what system you have but checking at the pump may not be accurate as there may not be a lot of air volume behind to stabilize. I think the best place would be at the head or at the inlet to the vac tank.

I get 12 in. Hg at the head, too. And my “at the pump” means the inlet to the vacuum accumulator (removing the inlet sanitation hose).

I've actually toyed with the idea of adding a permanent vacuum gauge at the sanitation hose inlet side of the vacuum accumulator. It'd just make it super easy to troubleshoot the system at a glance and avoid unnecessary duck bill changes or disassembly. Any system that can build/hold proper vacuum ought to not need duck bills and the problem would lie elsewhere.

 

[Jeepers]

Adjust the switch. Don't let the screw twist, you will rip the membrane.

 

[mobocracy]

Adjust the switch. Don't let the screw twist, you will rip the membrane.

From what Google turned up, the switch isn't adjustable. I kind of poked at it and couldn't find an obvious means of adjustment. It would be a money saver if it was adjustable.

Maybe that design is super reliable, but it feels like its maybe just a tad bit too mechanical having the spring mechanism actually actuate the shutoff switch. I think it would be kind of nice to have an electronic vacuum sensor with a little gauge and an adjustment screw for cut-in/out vacuum levels.

 

[Lazy Daze]

Those switches are lovingly referred to as a "10-year switch". Some last longer. Easy replacement.

 

[mobocracy]

Those switches are lovingly referred to as a "10-year switch". Some last longer. Easy replacement.

Well, this boat has gotten 14 years out of its 10 year switch, so maybe I don't feel so bad.

I've bought parts for this from Seacoast Services and the guy on the other end of the phone has been super valuable in troubleshooting. I talked to him this morning and his opinion is the switch, too, with the system making 12 inches Hg vacuum and holding it but the pump not shutting off.

He also said the reference range for vacuum is something like 9-11 inches Hg.

 

[Lazy Daze]

Yup - when you can fiddle with the switch with your finger and make it work, that's pretty much the normal "diagnostics" I've often wondered if spending some time trying to clean them would work... but never actually tried when replacing is quick and easy and you're back up and running.

 

[mobocracy]

Yup - when you can fiddle with the switch with your finger and make it work, that's pretty much the normal "diagnostics" I've often wondered if spending some time trying to clean them would work... but never actually tried when replacing is quick and easy and you're back up and running.

Do you know if these switches are adjustable? I've read mixed opinions about that. I figure as mechanical as they are there must be some kind of tolerance adjustment, but maybe because they use a spring there's not really any adjustment.

I also suspect that the actual problem with it isn't the actual microswitch, it's some kind of mild and treatable corrosion increasing friction on the spring mechanism or possibly residue on the diaphragm which results in a loss of sensitivity.

Maybe another reason why some kind of pressure sensor which produced an electrical value and a cut in/out switch which could be adjusted as needed would be superior. If you had a sensor with a potential range of 20 inches of Hg, you could just twist a pot on the switch to cut in/out at a good working vacuum as the sensor maybe lost a few inches of accuracy.

I'm definitely going to screw around with the old pressure switch to see if there's any obvious cleaning/refurb that could be done and maybe keep it as a spare.

 

[Lazy Daze]

I don't know if they're adjustable - for the same reason... it's quicker and easier to just pop a new one in and be done with it.

I agree with your second paragraph - I believe something like what you said is the reason... that's what has me wondering about trying to clean it.

There's no reason why another type of switch couldn't work - it's essentially just performing the duty of "on/off". However... would another type of switch last as long? Longer? Shorter? I dunno!

 

[mobocracy]

There's no reason why another type of switch couldn't work - it's essentially just performing the duty of "on/off". However... would another type of switch last as long? Longer? Shorter? I dunno!

I guess I'm thinking of a switch which has two parts. A linear pressure sensor that converts vacuum to some electrical value and a switch that trips in/out based on that electrical value. Since you'd have more range than a fixed spring "sensor", you could adjust the switch's cut in/out vacuum level.

It should last longer (or have a longer useful lifetime) because small losses in pressure sensitivity could be adjusted away.

The downside would be more cost (and a power tap to run the sensor, since it wouldn't just be a dumb switch), but honestly it should have a longer useful life since a loss of 10% sensitivity wouldn't cause it to just not work anymore.

 

[Happy Hour IV]

they manual says it is calibrated at the factory, do not adjust. why would it say this if there was no way to adjust. the switch has a knurled thumb wheel against the spring. turn it compress the spring and cutoff pressure goes up. turn it to decompress spring and vac pressure goes down. set for 10 in.

 

[Jeepers]

There should be a slot in the end of the screw. Secure it with a screwdriver before you turn the thumb wheel or else the entire thing will try to turn and rip the membrane.

 

[Happy Hour IV]

Good point about twisting the membrane, I used needle nose pliers with little pressure on the threads so it could be adjusted while in place. don't squeeze to hard and ding up the threads.

 

[mobocracy]

Gah… it goes from bad to worse.

Got the replacement switch, dropped it in and….failure. With the new switch I’m only pulling 9.5 inches of Mercury on my vacuum gauge. A week ago it was nearly 12”.

Swapped new for old, same issue. Decided to swap in new duck bills and O rings. No improvement, although the old bills were ready to retire based on visual inspection.

Pressure at head matches vacuum accumulator inlet vacuum readings. Everything is snugged down as tight as I dare.

I did tear apart my old switch and discovered how to adjust it. I think they use loctite at the factory for holding the thumb wheel. It took serious effort to loosen it. While testing the old switch today it easily adjusts for pressure.

At this point I’m kind of giving up for now and just using the head in “key switch” mode — turn on key switch, do business, flush, wait a couple minutes and then turn off key switch. System generates enough vacuum to use.

Not sure where to go next. I am sort of tempted to put some small rubber o rings on the vacuum switch mounting holes. They penetrate the vacuum accumulator body and since swapping the first time is where I lost vacuum initially, I’m kind of suspecting a small vacuum leak there. Possibly that and some tub sealant on the mounting screw threads.

My step after that is to just give up and put a timer relay between the vacuum switch and the pump motor. Let the pump run for 3 minutes and then let the relay turn it off. Bonus is that I don’t get burned at anchor with a runaway pump that doesn’t shut off.

 

[carterchapman]

Gah… it goes from bad to worse.

Got the replacement switch, dropped it in and….failure. With the new switch I’m only pulling 9.5 inches of Mercury on my vacuum gauge. A week ago it was nearly 12”.

Swapped new for old, same issue. Decided to swap in new duck bills and O rings. No improvement, although the old bills were ready to retire based on visual inspection.

Pressure at head matches vacuum accumulator inlet vacuum readings. Everything is snugged down as tight as I dare.

I did tear apart my old switch and discovered how to adjust it. I think they use loctite at the factory for holding the thumb wheel. It took serious effort to loosen it. While testing the old switch today it easily adjusts for pressure.

At this point I’m kind of giving up for now and just using the head in “key switch” mode — turn on key switch, do business, flush, wait a couple minutes and then turn off key switch. System generates enough vacuum to use.

Not sure where to go next. I am sort of tempted to put some small rubber o rings on the vacuum switch mounting holes. They penetrate the vacuum accumulator body and since swapping the first time is where I lost vacuum initially, I’m kind of suspecting a small vacuum leak there. Possibly that and some tub sealant on the mounting screw threads.

My step after that is to just give up and put a timer relay between the vacuum switch and the pump motor. Let the pump run for 3 minutes and then let the relay turn it off. Bonus is that I don’t get burned at anchor with a runaway pump that doesn’t shut off.

It may be time to replace the bellows.

 

[mobocracy]

It may be time to replace the bellows.

They were done 5 years ago. Time again so soon?

 

[carterchapman]

That's what brought my pressure up when my switch wouldn't cut off even after I replaced the switch...5 years is a good run. Some may get longer, but that's all you've got left if water is staying in your bowl and you hear no leakage by the foot pedal.

 

[brewster16]

....following

 

[mobocracy]

That's what brought my pressure up when my switch wouldn't cut off even after I replaced the switch...5 years is a good run. Some may get longer, but that's all you've got left if water is staying in your bowl and you hear no leakage by the foot pedal.

Yeah, I guess, a lot of it just denial because I don't wanna do the work. The good news is that I have the bellows parts kit already bought from a previous years' Vacuflush-isn't-working situation. As seasonal boaters with a shorter season, I've been able to get away without annual duck bill changes, maybe my periodic replacement should always just include a bellows replacement, for sanity if anything else.

I still think it's odd that my initial troubleshooting with my vacuum gauge saw nearly 12" of Hg vacuum but as soon as I pulled the old vacuum switch and replaced it, I'm down to 9-10" Hg. I mean my initial problem wasn't a lack of generated vacuum in the system.

I have to admit, if I was making some kind of choice about toilet systems I would be easily swayed to not install a Vacuflush system and get one of the electric kind that macerates and pumps to the tank with positive pressure. I have so far found my vacuflush system to be just too quirky and prone to throwing parts at it (some of which is due to age) and a lot of messy diassembly along with those parts.

IMHO it would also help if the system was modernized. Replace the spring vacuum switch with an electronic sensor switch with a vacuum readout -- this alone would greatly improve troubleshooting. It could also be easily adjustable for cut-out pressure.