Black Tank Flush - Montana Owners Club

CamillaMichael · 11-22-2010, 01:53 PM

The Owner's Manual tells us to "Open the water supply to full pressure to flush tank." This refers to the "auto" black tank flush located in the utility center. Does anyone happen to know how much pressure the black tank flush can withstand? The reason I ask is that at a campground in PA I had a "water splitter" attached to the fresh watch pipe at our site...on one side I had a water regulator attached and then our freshwater hose to it. The other side was closed with the toggle switch. I was intending to connect a grey hose to that side in the am to complete the tank draining process. Well, about half an hour after setting up there came a rapping on our door...a neighbor told us our water hose had burst! As it turned out, the water hose was fine...the water regulator was doing its job just fine. However, the other side of the water splitter was not so fine...the high water pressure had blown out the seals around the ball/toggle mechanism. So, with all of that in mind, I am a bit concerned about the notion of turning the water to "full pressure" going to our black tank assembly. Thoughts???

oldelmer1 · 11-22-2010, 02:45 PM

WOW, that sounds like a lot of pressure. Put your pressure regulator at the faucet, then connect your hoses from there.

CORattler · 11-22-2010, 03:48 PM

I agree with Tom. A adjustable regulator is especially useful as you can determine the pressure YOU want to send to your rig or other device.

CamillaMichael · 11-22-2010, 04:03 PM

Quote:

quote:Originally posted by CORattler

I agree with Tom. A adjustable regulator is especially useful as you can determine the pressure YOU want to send to your rig or other device.

The first few times I used the black tank flush, I had a pressure regulator attached to the hose leading to the black tank flush and noticed little to nothing was actually happening...I interpreted that to mean that the system required a fairly high water pressure to work. I just do not know how much pressure the system can take. I obviously want the black tank to be flushed, but do not want to blow the system through the side of my Montana!

stiles watson · 11-22-2010, 04:05 PM

Unless the pressure is extraordinarily high, I don't think you have an issue. When you turn on the wash the valve is open, so where is the build up of pressure? It is flowing through the spray nozzles. When you turn it off, you do so outside the rig. The only place the pressure builds is before the valve.

CamillaMichael · 11-22-2010, 04:54 PM

Stiles, I didn't think there would be an issue with the water splitter either, but!!!!! Without knowing how these tank flushers are attached and how they are constructed (getting construction specs from Keystone does not seem likely), I have to wonder how much pressure they can withstand. To answer your question, the water pressure is what it is...as it flows through the system...again, not knowing how they are constructed, the nozzles you mentioned might very well be blown out. Afterall, many rv components are not exactly sturdy. I have installed tank flushers in another rv and know those items were not what you would consider "industrial grade!" So, am I worried about this??? No, but I am concerned that if high water pressure was able to, essentially, blow apart a water splitter (did I mention it was not one of the cheap plastic jobs, I sprung for the metal one and spent the extra buck) that it might be able to do the same to a tank flush. You are probably right, there might not be an issue here at all, but if there is an issue I would sure like to know about it before I have a mess to clean up.... Thanks, Stiles.

HamRad · 11-22-2010, 06:02 PM

CamillaMichael,
I would not worry about there being too much pressure involving the black tank flush. It is an open system and I doubt there is enough pressure to cause any kind of problem. As a matter of fact I can't recall anyone ever reporting any problem with excessive pressure involving the black tank. There have been reports of various plumbing connections. Mainly leaking connections or kinked lines. Also problems with the check valve have been reported.

I always hook up my black tank hose to an unregulated faucet. I find that this allows for a better and quicker cleaning of the black tank. I wouldn't worry about too much pressure causing a problem with the black tank.

Good luck,
HamRad

ole dude · 11-23-2010, 12:21 AM

The water lines to the flush are more than likely the same material as the rest of the lines. Seems as though 60 or so lbs of water pressure is the tops. An open line is probably not going to be an issue, however, when cleaning, should you elect to fill the tank above the spray nozzles in the tank, the flow will meet with some resistance and could raise the pressure some what. How about a pressure gauge on the line to the black tank while you are flushing, this would give you the info you need and provide some piece of mind. In my mind, the back flow preventer in that particular line is the weak link.

stiles watson · 11-23-2010, 03:22 AM

Apples and oranges. There is a huge difference in seals being blown out of a valve on a splitter that is closed (and probably defective) and the water pressure build up in an open system. The open system releases the pressure. Granted orifice size can restrict flow and increase pressure, but as Hamm has stated, I haven't heard a report on open spray systems being blown apart by high pressure.

thor · 11-23-2010, 04:50 AM

when lushing your tanks .the valves should be open to allow everthing to come out .there should be little presure on the system when flushing.

richfaa · 11-23-2010, 05:29 AM

Well I do not know how much pressure they can take but we have been out nearly 5 years thousands of miles and scores of campgrounds without a problem. I know the pressure at home is 53psi and we have seen psi as high as 90 at campgrounds. A regulator does not hurt we have one and if in doubt will check the psi at a C.G.

CamillaMichael · 11-23-2010, 06:02 AM

Thanks to all...I believe it is always better to ask than assume all is well. The old saying "an ounce of prevention is worth a pound of cure" comes to mind. Stiles, the pressure at the PA campground, as I recall, was 100-110 psi...and I agree, the water spliter was likely deffective. Again, thanks to everyone who responded.

CORattler · 11-23-2010, 03:22 PM

While I agree that when operated per instructions the tank flush is an non pressurized system inside the tank, I would be concerned about running more than the stated max pressure of the RV lines. If the end of the sprayer has holes or slits it would be more restrictive than an open line. That means there would be greater pressure build up. Have you ever partially put your thumb over the end of a running hose? What happened? Increased restriction and pressure build up. The hose swells from the pressure. Personally, I restrict my pressure to 60psi. Just my 2 cents.

HamRad · 11-24-2010, 05:53 AM

My water lines are rated at 140 pounds per sq. inch. And I suspect that they will handle even more than that. Also in our 5+ years on the road We've NEVER seen pressure higher than 120. The vast majority of systems run in the 60 to 80 psi. The risk of damage to your black tank flush system from excessive water pressure is probably less than a few percentage points.

If you want something to worry about I'd suggest your tires and or your suspension systems.
You are much more likely to have a failure in one of these items than you are with the black tank flush system.

Good luck.
HamRad

CORattler · 11-24-2010, 02:42 PM

Are all Montana's rated at 140 psi? Where did you get this info? Thanks for the enlightenment.

Quote:

quote:Originally posted by HamRad

My water lines are rated at 140 pounds per sq. inch. And I suspect that they will handle even more than that. Also in our 5+ years on the road We've NEVER seen pressure higher than 120. The vast majority of systems run in the 60 to 80 psi. The risk of damage to your black tank flush system from excessive water pressure is probably less than a few percentage points.

If you want something to worry about I'd suggest your tires and or your suspension systems.
You are much more likely to have a failure in one of these items than you are with the black tank flush system.

Good luck.
HamRad

CamillaMichael · 11-25-2010, 01:59 AM

Quote:

quote:Originally posted by HamRad

My water lines are rated at 140 pounds per sq. inch. And I suspect that they will handle even more than that. Also in our 5+ years on the road We've NEVER seen pressure higher than 120. The vast majority of systems run in the 60 to 80 psi. The risk of damage to your black tank flush system from excessive water pressure is probably less than a few percentage points.

If you want something to worry about I'd suggest your tires and or your suspension systems.
You are much more likely to have a failure in one of these items than you are with the black tank flush system.

Good luck.
HamRad

Did not say I was "worrying" about this issue...my "concern" is having a cheap, plastic fitting blow apart inside a not-so-easy to reach place. I do, however, worry about having waste water leaking out into the rest of the trailer. Thanks for the info on water pressure numbers...any idea of where the weak link (any component, like water heater???) might be within the closed water system???

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