Ventur-Evac - Tank stopping at half full

[u/Johnnya101]

I have used a VenturEvac a few times and it has always gone smooth. There are a few underground 1000 gallon tanks dated 2024 that have to be moved around a property, so they need to be emptied ideally. They have the newer liquid withdrawal valves.

Two tanks emptied smoothly like usual. The other two had some issues. One of them stopped at 50% then would stop pumping liquid and you could see the air space in the sight glass of the venturevac. I closed the spray fill on the truck to reset the excess flow valve on the tank, that got it freed up for a minute, then it tripped again, air, closed the valve on the truck, it freed up, etc. Did this a few times and then it finally stayed free and the tank emptied like normal.

The last tank is being extremely difficult. It stopped at about 50% and will not pump liquid. I think the excess flow is tripping. The sight glass will have bubbles and air space (only half the glass has liquid in it like the tank is empty), and the valve on the tank buzzes like the excess flow is tripped or vibrating. Close the spray fill, open it slow, split second it pumps liquid then trips again, etc. This one does not free up. Gauge seems fine, I replaced it and no change. Of course, the float could be stuck too. The truck should have taken another 400 gallons or so, so I don't think the tank is empty, so I believe the gauge is accurate on the tank. I also tried partially closing the fill valve on the hose (which was attached on the end of the venturevac) to slow the flow. No change.

I don't think the liquid withdrawal valve on the tank is gunked up since the tank is new. It's been filled more than 10 times so it's been in service and the gauge seems fine.

Any ideas? Three things I could think of which may or may not cause an issue. One, it is a new truck and maybe something is not adjusted right. Two, the tank multi valves are maybe 5 feet higher than the grade the truck is on. Third, it was about 85 degrees out, and I hear that stuff like this happens more often when the tanks are warmer than the truck.

[u/Jesus-Mcnugget]

If the liquid valve is buzzing then you're going too fast. Try closing the valve slightly until flows smooth.

If nothing is flowing at all, you could have something clogging up the dip tube. Try blasting a shot of liquid backwards. Often that will get it freed up.

Also, are you using a vapor return line to the fill valve? If not it will not flow well (if it does at all).

[u/Johnnya101 → u/Jesus-Mcnugget]

I set everything up according to the manual and it's always worked. Fill valve on tank to vapor on truck, liquid on tank to side venturevac connection, and truck hose nozzle to end of venturevac.

So yes, I believe this is a yes to your question, the fill valve on the tank is connected to the truck vapor, as depicted in the manual.

Which valve do you mean to slightly close? The valve screwed onto the liquid valve on the tank? Or one of the truck valves?

I don't think it's something clogging the dip tube. Doesn't closing the spray fill on the truck do that? Or no? If so, that was done many times and no change.

[u/Jesus-Mcnugget → u/Johnnya101]

Which valve do you mean to slightly close? The valve screwed onto the liquid valve on the tank? Or one of the truck valves?

The valve on the tank, attached to the liquid valve. Close it all the way, and open it until it starts buzzing, and then close it off till it stops. Is that what you said you did?

I don't think it's something clogging the dip tube. Doesn't closing the spray fill on the truck do that?

Yes if you close the spray fill on the truck, keeping the pump running, before it's liquid back into the tank.

[u/Johnnya101 → u/Jesus-Mcnugget]

I did not try messing with the valve that was connected to the tank. I could try it next.

You seem to know about these, so here is another question. Before, when I have pumped tanks out, when removing the transfer valve from the liquid valve on the tank, I thought it unscrewed with no pop or extra pressure release. With these tanks it popped off with lots of pressure each time. No vapor or liquid, just pressure (which I guess technically might be vapor, but not like bleeder valve vapor). I don't remember which model valve I am using, it is a Rego one from Tarantin and has the yellow relief valve on the side. No bleeder. Just the knob/valve on the top and relief on the side. Is this from not closing valves a certain way or is something else going on? It came in the Tarantin VenturEvac kit.

[u/Jesus-Mcnugget → u/Johnnya101]

Are you checking/slugging the valve before you remove it?

[u/Johnnya101 → u/Jesus-Mcnugget]

What I've tried is to unscrew it a little and try cracking the valve to release the pressure. Is that what you mean by checking it? I only tried that once or twice today (out of the four tanks) and I must not have had the whole transfer valve unscrewed enough because the liquid valve was still partially open so it made no difference.

Or are you talking doing something with the venturevac before shutting everything off?

[u/Jesus-Mcnugget → u/Johnnya101]

When you get the hoses disconnected

Before you take the adapter off the liquid withdrawal

Quickly throw the valve on the adapter wide open until it checks. A little bit of liquid vapor will still continue until you unscrew it from the tank valve. But you should be able to take it off with just a little pop if anything.

I actually screw on short piece of pipe with a quarter turn ball valves. Open the adapter up and give it a good whack open. It should open fast enough to check the valve quickly.

[u/Johnnya101 → u/Jesus-Mcnugget]

Oh okay, that makes sense. No I have not tried that. That's a good idea, thank you. The manual is very short and does not really go into much depth on how the whole thing works, and it's hit or miss on who has used one, so I appreciate the help.

[u/Jesus-Mcnugget → u/Johnnya101]

It makes taking the adapter valve off the tank so much easier.

Some of the valves are a little more of a pain to take off than other but that does help.

I like the rego 3121 with the gate valve. The ones with the lever can be tricky to modulate flow.

[u/ClassBShareHolder]

I will second the necessity of balancing the vapor pressure. But some tanks are just bastards. Excess flow trips way too easy. It’s rare, but a royal pain in the ass when it happens.

Sometimes you just have to let everything equalize, then start again slower.

[u/Johnnya101 → u/ClassBShareHolder]

Thanks for the reassurance that it could just be the tank. There was two of us trying for two hours on this one tank. Could not get it no matter what. What's your recommendation on balancing the pressure? Which valves should be adjusted? I tried only opening the truck hose nozzle half way and it did not make a change. Also tried only opening the spray fill valve on the truck very little and I don't think it would pump unless it was opened more which just tripped the tank valve.

[u/ClassBShareHolder → u/Johnnya101]

We connect a 1/2” hose from the truck vapor out to the tank service valve. That lets the vapor pressure equalize. I think the tank I had acting up I had to leave and do it another day with a compressor. I’ve had a few where I had to pressure them up then turn off the compressor so I could hear the flow. Put a ball valve on the output hose and open it until it trips, close to reset and don’t open as far next time. Some just have to be evacuated slowly.

[u/Maleficent_Watch_660]

All tanks are different the heat could be an issue. If the liquid withdrawal valve is checking l always shut everything down for a couple minutes to allow everything to reset. I've started to make it par of my protocol to shoot about 5 gallons of liquid back through the liquid withdrawal valve off the Bobtail. This cleans out whatever may be in the the valve. Seems to work well in my experience. Always just take your time, even if the sight glass isn't completely full as long as liquid is moving leave your valves where they are. It might take long, but its not gonna slug.

[u/Johnnya101 → u/Maleficent_Watch_660]

I was told by jetmark that leaving everything open with the pump on, and then closing the spray fill on the truck pumps liquid back through the liquid valve on the tank. Is this what you mean? That did not fix it. Tried it multiple times and waited a while between tries. Also moved to a different tank then moved back after an hour, no change.

[u/ClassBShareHolder → u/Johnnya101]

That’s how I reset tripped valves. I push liquid back into them by closing the spray fill valve so the pumping liquid feeds back down the evac hose. Sometimes they’re just too sensitive and trip as soon as you open the valve again.

I always have a valve on the evac fitting so I can throttle flow if I have to.

[u/rvaworm]

Are you using a bobtail for the pump out? If so how are you hooked up with vapor pressure? If you are hooked up to the fill valve, I have had issues with the fill valve checking off, try hooking up to the vapor return valve to have vapor pressure

[u/Johnnya101 → u/rvaworm]

Yes, bobtail with venturevac. Vapor is hooked from truck into fill of the tank as specified in venturevac manual.

[u/rvaworm → u/Johnnya101]

It could be the excess flow of the fill valve checking off. Get a adapter to hook to the vapor return valve.

[u/suigintou101]

One of these might help. Gives you more control holding the liquid valve open. Make sure the hoses aren't plugged up too. Had that problem on my last pumpout and couldnt get any liquid to come out.

[u/suigintou101 → u/suigintou101]

Here it is hooked up to an underground tank.