Ever freeze that water line? (cold weather)
Ever had a vapor-lock condition in that line? (hot weather)
No, the gauge, regulator, and all the plumbing to it has been environmentally controlled since day one. So no freezing or boiling. We have pets, so we need to keep the coach within reasonable living temperatures even when we are away from it.
Ever run out of flush water?
Yes. We normally keep the pumps on 100% of the time, but on occasion we have turned them off for whatever reason, usually because one of the hot water recirculating valves is leaking and we are trying to preserve the hot water. Once in a while we forget the pump is off, and try to flush the toilet anyway. This always has bad consequences, since the cycle valve in the Microphor depends on having both air and water pressure to it at all times. I'm certain this causes the pressure to drop to zero, but since this gauge is on the output side of the regulator, that should be a gradual drop-off.
Have you ever drained your system.
If you had a hose attached to you water system and stretched out downhill you "could" pull enough vaccuum to see what you have recorded with the bent needle.
We've never drained the pressure side of the system. There is a check valve on the city water inlet, so even with a hose attached, there's no way for the pressure to drain out that way. We never use city water pressure, as a rule, either. I think we've been hooked to city water maybe three times in six years, and in all cases it was either for testing or to do maintenance on the pump. Generally, even when city water is available, we just fill our tank and use our internal pump for pressure.
How about a pressure spike slamming the needle full around against the stop bending it.
As has already been mentioned, that would have bent the needle the other way. The bend in this direction can only be cause by hitting the zero stop on the downward swing.
As a instrument tech in a previous life, this looks like a water hammer to me.......! When stopping a pump this happens, also can happen when valves close quickly.
OK, we've had some hammer. Generally this happens when we run out of fresh water in the tank, and the pump ingests some air into the lines. We'll get hammer until we purge all that air out. I can't say that I've watched this gauge when this happens, but next time I will.
Putting a dampner pressure gauge would help prevent this if the gauge is that important but probably not worth the price in this use!
That is surely true. Same for the earlier recommendation to change to oil-filled. I want to figure out what caused this, but it's not worth it to me to fix the gauge itself. It's only purpose was to adjust the water pressure initially, and it's not mounted anyplace where it can even be seen in normal use.
I thought you had a small pressure tank in your fresh water system?
No, we have Sensor VSD pumps, which do not require an accumulator tank.
I would think that would prevent an excessive drop in pressure on the line when the toilet is flushed, but
maybe not if the line is small and the gauge is on the output side of the regulator (which it certainly must be).
The supply line to the regulator is 1/2' ID, as are all our water lines (PEX). From the regulator to the fixture is one of those braided stainless connector hoses from the hardware store. That said, I would guess the orifice in the regulator to be much smaller, say 1/8" or less.
I do believe yours is related to the small line it's on and the very low volume between the regulator and toilet. I don't fully understand why you have it on there? Does your toilet require
something less than 60 lbs?
Yes. The way this contraption works, the cycle valve controls the timing and operation of the flapper door, the blast of compressed air that shoots the waste to the tank, and the refill of the bowl. The cycle valve has no adjustments on it. Timing and operation are controlled completely by pressure and flow rates in the air and water supply. Microphor requires a dedicated regulator on the air supply, set to 60psi, and we have always had that. They also strongly recommend a dedicated regulator on the water supply, too. We tried to live without one, since we always run just on pump pressure and that's a pretty constant pressure.
The problem with that was that our pump pressure delivered water to the system at a rate that cause the bowl to fill too far. We tried for a long time to control this with a gate valve at the fixture, adjusting the orifice down to a point where the flow was lower. But that was unreliable, and especially when there was any variation at all in delivery pressure, such as when connected to city water (rarely), or after a change in battery voltage such as turning the charger on, which creates a temporary pressure surge the next time you turn the water on.
Ultimately, we gave up and sprung the money for a small individual regulator at the fixture. Then we dialed the pressure at the fixture down until we got the minimum amount of water in the bowl. The spec calls for two quarts per flush, and before we installed the regulator, we were using much more than that -- I would say closer to two and a half quarts. When you spend two weeks at a time in the desert, that extra pint every flush takes a toll both on the fresh water supply and the black tank capacity.
I remember the regulator as being quite spendy, like around $40. It was available with or without a gauge, and the gauge was only a couple bucks extra, so we got it, even though we really use the amount of water delivered to the fixture as the yardstick for adjustment, rather than the pressure reading.
As you can see in the photo, we have the pressure dialed down considerably. So you can imagine how much extra water we'd get at a much higher pressure.
BTW, they make a pressure regulator for garden use that regulates to 35 psi with no gauges or adjustments. It simply screws onto a standard hose bib fitting. I believe I have one here.
If you are interested in using something like that, I'll dig it out and send it to you.
Thanks, we've got a couple. We use them in those rare cases where we need to connect to city water to bypass the pump for maintenance. While our entire water system is rated for pressures far in excess of that, our own skin is now calibrated for the pressure delivered by our on-board pump, and we find ourselves having to fiddle too much with faucets and shower valves if we have significantly higher pressure than that at the taps.
The garden-hose style regulators made for RV use do not have the fine adjustment required for the Microphor application.
The good news is that installing the regulator was the right solution, and everything has worked perfectly since then. I would not even have noticed the bent pointer if we did not pull the toilet out for other reasons. It's not so much a problem as a curiosity at the moment. I've never seen this behavior, and I want to understand it, so the next guy with a Microphor who asks me for advice can benefit from that.
Bourdon tube pressure gauges do not tolerate chronic big pressure swings over and over again without going out of calibration. ... They don't last long. If the gauge went out of cal, it would allow it to hammer against the stop with each flush. It would be curious if you knew where you set the pressure on the regulator initially, and where the pressure reads when you install a new gauge.
Aha! This is the best answer I have heard yet. Now that you ask: No, I don't remember what I had the pressure set to. As I wrote above, we set it by delivery volume, not pressure. But my fuzzy memory suggests perhaps somewhere around 30 psi, and the photo clearly shows the straight portion of the needle aiming somewhere closer to 20 psi.
I'm not sure it's worthwhile to replace this gauge. But if I come across a reasonably priced replacement in my travels, I'll do it just to answer this question.