Black Water Flush

[martybmw]

My 21 Alpine 3700FL is parked full time and as a result not able to take advantage of the sloshing around when driving to help clear the sensors. I have two inlet valves maked tank flush and am assuming as I have two black water tanks these are for them as not labeled. We are off grid and the water pump that I use only puts out around 12 LBS of pressure and wonder if this is enough to have any impact. In the manual it doesn't break down the capacity of the 2 black water tanks (and boy is the front 1/2 bathroom toilet capacity small).

[Martian]

If you put a check valve in line you could use the outside shower and the pump. Put the check valve right before the flush connection. That might give you enough pressure to clean the sensors IF they are opposite the nozzle. They are not always opposite. They are where the easiest spot to put them was.

[chuckster57]

Your onboard water pump should be 40+ PSI unless something is wrong.

[JRTJH]

Originally Posted by martybmw

My 21 Alpine 3700FL is parked full time and as a result not able to take advantage of the sloshing around when driving to help clear the sensors.
...

In the manual it doesn't break down the capacity of the 2 black water tanks (and boy is the front 1/2 bathroom toilet capacity small).

As for the "effectiveness of the spray pattern" on any RV black tank rinse nozzle, take a look at the typical nozzles installed on RV's and you'll see that there's just not any "high pressure spray" with any of them. Black tanks are "filled with cleaner water" and then when that's flushed or dumped out, the velocity of the water leaving the tank takes much of the waste with it. Unless you have "unlimited fresh water and unlimited black tank disposal at your site" then trying to flush the black tanks with the installed black tank rinse nozzles will take an enormous amount of time, fresh water and multiple dumps to get anywhere even close to "sort of clean"...

Honestly, to "clean the sensors relying on the spray produced by anything that Keystone installs would be a stretch of the imagination.

You can visualize the spray patterns in this video:

https://www.youtube.com/watch?v=Lf4p1CpfgOs

The actual demonstration starts at around the 4:00 mark in the video.

It's just my opinion, but most owners do have problems with the sensors reading correctly. You'll hear people say their sensors are accurate and always have been, but for every ONE of them, you'll hear 20 say their sensors worked the first trip and have not worked properly since then no matter how hard they try to clean them, they may work one more time, then foul again. So, back to my opinion, if you want accurate sensors, get the Garnet 709-4 SeeLevel II 4 Tank Monitoring System installed. It's $300 for a 4 tank kit and requires the bottom coroplast cover on your trailer to be removed where the tanks are located to install the kit. Is it worth the expense and effort to you?? Only you know how much you want "accurate tank gauges"... For me, I listen to the "gurgle when flushing" and that's been my standard gauge for the past 20+ years of RVing with a tank gauge system. Simply put, the "nails with a plastic cover used by Keystone and called gauge sensors" are problematic for everyone and ignored by most.

Now, your comment about the forward half bath black tank filling rapidly. Here's what I think you actually have installed:

4 waste water tanks, 2 black and 2 gray

TOTAL black capacity is 78 gallons
TOTAL gray capacity is 78 gallons.
That means 4 actual tanks, each with a 39 gallon capacity.

Here's what I think you'll find if you do the "bucket dump while counting actual gallons"...

The rear black tank receives ONLY waste from the rear toilet
The rear gray tank receives waste from the rear sink and rear shower.
The front black tank receives waste from the half bath toilet AND sink.
The front gray tank receives waste from the galley sink.

So, you have ONE toilet filling the rear black tank and you have ONE toilet AND ONE sink filling the front black tank....

You can verify this easily by just closing the front black tank dump valve, turning on the half bath sink cold water faucet and watching whether the front black tank or the front gray tank fills... My bet is that your black tank will fill with ONLY the half bath sink being used in the test....

That will explain how you get the impression that the front black tank must be smaller because it fills faster... It is filling faster, even though all four tanks are 39 gallons each.

[bobbecky]

This link is the Trekwood page that shows tanks for you model and year. The two tanks at the top are likely a black and a grey tank that sit next to each other, as they have a left and a right discharge port, and both are 33 gallons. The large tank on the next row is 48 gallons and the next one to the right is 44 gallons. It is likely that you have one each of the 33 and 44 gallon tanks for the black and both for the grey tanks. https://www.trekwood.com/parts-searc...23+%2F+Keyword

[martybmw]

Johna and all thanks for the responses probably just going to have to live with all my sensors out of whack. Even my fresh fill is pretty much worthless. When I fill it after using maybe a gallon or 2 it goes to 1/4 full.