Help making liquid reservoirs FIFO

[Crapgame]

In the attached image, the water flows from the top into right tank until full, then middle until full, then left until full.

That part is fine.

However, when I decide to open the output (to the right of screen) for some reason it starts by emptying the FIRST tank instead of the leftmost tank.  Once it drains that one, it moves to the middle tank and then finally the left tank.  Obviously, I'm disinfecting this water and I'd like it to draw from the tank that has been in there the longest.

I'm sure this is a pipe priority issue (it always is) but I've tried all kinds of combinations and it still wants to draw from the righthand tank.  I use the pipe priority chart that I've found here to solve most issues but this one is vexing me.

Any advice is appreciated.

 

[Neotuck]

If the plan is to disinfect water in a chlorine environment then I suggest building the liquid reservoirs on top of mech doors that you can automate.  When the door opens it disables the reservoir preventing liquids from leaving, but it can still receive liquids.  

Here's a simple setup I use for bathroom loops, the germ sensor opens the door and a BUFFER gate prevents the door from closing for 135s enough time to kill all germs.  The second germ sensor controls a shutoff to send any surviving germs back into the reservoir

[KittenIsAGeek]

8 hours ago, Crapgame said:

However, when I decide to open the output (to the right of screen) for some reason it starts by emptying the FIRST tank instead of the leftmost tank. [...]

Alright, what's actually happening is that your tanks are always draining when possible.  So, if your left-most tank sends a packet of water out, then the center tank can sent a packet out, and the right-most tank can send a packet out.  Thus when you start letting water out of the left-most tank, the right-most will empty first, because the water is continually flowing into the next tank.

@Neotuck's example above shows how to disable a tank so that liquid doesn't flow out of it. You could also use liquid shutoffs.  With the new automation outputs on the tanks, you could easily do what you need by using either doors or shutoffs.

The idea is that you want the left-most tank to empty first, then refill it with the liquid from the center tank.  So you could set the automation of the left-most tank to "High: 100, Low 0" and send the automation output to either a door under the central tank or a shutoff.  You can also send the output through a "NOT" gate to a valve or a door controlling the tank itself.  So what will happen is that when the tank is empty, the output will be disabled for the left tank, and the output will be enabled for the center tank.  The center will fill up the left tank, and when its full the automation will disable the output of the center tank while re-opening the output of the left tank.

[Crapgame]

Thank you both.  I will try these solutions and see how it goes.

I'm relieved that this isn't a pipe priority issue and that some additional mechanism is required to get the desired result. 

 

[StoneToad]

If you just want to fill from right to left and empty from left to right, run the input pipe across all 3 tanks from right to left, and the output pipe across all three tanks from left to right.

When a packet of water comes in, it will first try to go into the right tank, if it's full, it will go to the next and so on

When a packet of water tries to exit, it will exit from the left most tank, if there's any water in it, and flow to the right, blocking the outputs of the other tanks until the left tank is empty, and so on.
Edit: Note that with the new automation output on tanks, the full rate 3 tank disinfection method is trivial, just have your tanks chained as you do now but with mechanical airlocks under them (not powered) and wire to the tank above with automation wire.  Then set the tanks to high 99 and low 98, this will cause the tanks to fill up completely and stay no less then 98% full, and due to how ONI deals averaging germs in/out you'll end up with no germs coming out the last tank as long as they're all 3 in chlorine.

Here's a link one of to the original threads if you want to look at all the gory details.  Note that I've had problems with Neotuck's simple method he linked above because the germ sensor sticks at the last output value for me (germs all the time) and don't have good luck where clean PW resets it as I think it does in his, so I just use a pair of tanks (first to buffer while 2nd is disinfecting) the PW with 200s in the 2nd tank which is more then enough for toilet water.

 

[Neotuck]

54 minutes ago, StoneToad said:

Note that I've had problems with Neotuck's simple method he linked above because the germ sensor sticks at the last output value for me (germs all the time) and don't have good luck where clean PW resets it as I think it does in his, so I just use a pair of tanks

Ya I should point out that you need showers to provide clean PW to reset the sensor when it sticks.  Luckily element sensors also work and don't stick

[Emeal]

I recommend this setup from Tony Advanced.
This designs gets past the requirement of a germ free polluted water to reset the sensor.
The design can been seen on youtube here https://www.youtube.com/watch?v=tBGeCauVpkY

Good luck!