vacuum relief valve operation at low pressure?

animattanimatt Solar Expert Posts: 294 ✭✭✭
I have several 55 gallon drums located about 300 ft away from a small water tower.  The water tower supplies water around property to several stationary tanks connected by 1/2 irrigation hosing.  While flow rate is low, it is not a big deal as tanks located around the property eventually get filled.

Now I have several 55 gallon tanks that are located between some of the stationary tanks.  I currently just tee into a irrigation hose and put a garden valve there and I manually operate.  I fill thru bung on top of barrel.

  In the 55 gallon drums there is a 1 inch outlet.  This 1 inch outlet has low pressure but has a good flow which is useful.  As can be imagined water flow from hose bib to refill drum is kind of slow.

I would like to automate it a bit more.   I could cut top off of drum and install a simple fill valve like kind found on toilets. But would like to keep barrel sealed. and keep it cheap for now.

I am slowly increasing to better/larger more permanent water piping around the property.  But it slow going. 

I am thinking I can connect irrigation tubing directly to the 55 gallon drum and install a vacuum relief valve into one of the bungs. 

Main question is at such slow flow rate out of the irrigation tubing would the vacuum valve have a hard time sealing?  I guess i could just try. but looking for opinions first.  Property is located in mexico, and i would probably be bringing valves with me from states.  I could try just a single valve but would delay things a bit. 

I guess a secondary question.  Static pressure on drum would be about 8 psi although would have to check elevations to make sure. I don't see that being a problem with bottom and side walls but top may have issue with that bulge etc. .  They are plastic drums.

open to suggestions,

matthew wright


  • mcgivormcgivor Solar Expert Posts: 2,645 ✭✭✭✭✭
    Using a sealed drum is difficult because when filling the water will displace the air and actully compress the air until it reaches equilibrium, so a pressure relief valve would be needed, conversely when draining, if it were full, would require a vacuum relief valve. Sounds like a bit of a dilemma, but there is always a solution.

    If the level of the water tower is not excessively higher than the barrel, a vertical vent pipe equal or greater in height to the tower would allow the filling to terminate when the level is the same. Once the level is the same, there would be no flow, when draining the barrel, the water would actually be drawn from the tower as it would be attempting to ballance  the level, there would be no vacuum because it's vented to atmosphere, albeit at the level of the tower. This would be an automated system without any external automation, simply following the laws of fluid dynamics. When the tower is depleted, water would continue to flow from the barrel, the vertical vent would now prevent vacuum in the barrel, as well as the now empty supply from the tower. When water is again pumped to the tower, the barrels being the lowest point would be first to fill and air pressure  in the barrel would be vented to atmosphere through the vertical vent, when the tower is full, the barrels will be full. So not a sealed system but as close as possible, hope this makes sense, just typing what I'm thinking.
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  • animattanimatt Solar Expert Posts: 294 ✭✭✭
    If tower were shorter i would do just what you recommend .  

    But to my understanding vacuum relief valve would work both for filling and draining.  Just unsure what kind of pressure is needed to close VRV rather than have a partial close and weeping 
  • mcgivormcgivor Solar Expert Posts: 2,645 ✭✭✭✭✭
    edited April 2018 #4
    Is the tower higher than the barrel or barrels ?  The word tower would imply higher, but it really doesn't matter water will find its level regardless, a vacuum release valve would allow negative pressure to be released when draining, but when filling it would allow pressure to build, it's a one way valve.
     Edit. Water will find its level in an open circuit, example, if a hole were drilled through the bottom of Hoover dam and a barrel was connected with a pipe, without a vent, the pressure within the barrel would be equal the the total head of the water behind the dam. If a vent were installed on the barrel  to the top of the dam wall, there would be no pressure differential, it would simply be level with the water on the other side. Once a closed circuit is introduced everything changes.
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  • animattanimatt Solar Expert Posts: 294 ✭✭✭
     I am thinking about a valve that would normally be open. Like a movable float in the valve.  As water filled barrel air would escape. When water level got to height of float it would raise float and seal air escape and allow a pressure to start building.
    I guess I could be misunderstanding the valve. 

    Tower is roughly 30 to 35ft higher than tank level.  

    I do appreciate the explanation as you do not know my knowledge base. I already had a grasp of what you explained. But good to have it here anyway. 

    My knowledge is deficient with regards to valves. 

  • cow_ranchercow_rancher Solar Expert Posts: 112 ✭✭✭
    You can put a float type valve in thru the 2" bung, I've done it, it requires forceps that are made for large animals, you can probably buy them on ebay, they make a smaller float valve air float, it's used for poultry it fits thru the bung hole, try

  • BB.BB. Super Moderators, Administrators Posts: 28,588 admin
    Just a BIG warning--A 55 gallon drum will start to distort at ~8-10 PSI (start to assume a "balloon shape") and "explode" at ~35-100 PSI.

    The are not designed to take pressure, or vacuum (comment from Video: After 1 min it is down to around -0,3bar. and when it implodes it looks like it is down to between(-0.4 -0.44)bar):

    Remember that if you cycle the pressure, that will also weaken the barrel and cause early failures.

    If you need pressurized tank, use old (in good shape) water heaters with pressure relief valves (in US, typically set to 210F and 150 PSI).

    Do not re-purpose barrels for things that are not designed for.

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  • animattanimatt Solar Expert Posts: 294 ✭✭✭
    Cow rancher thanks for the recommendation . I was unaware of float valves that where so small. 
    Just ordered a few. That will keep drum un pressurized as well. 

  • animattanimatt Solar Expert Posts: 294 ✭✭✭
    As a side note. I belief my terminology was incorrect in above posts. I guess I was looking for a cheap air release valve (ARV) not a VRV.

    Air release valves are normally open at atmospheric pressure while VRV are already closed. If I find a cheap ARV I may play around with it as well.

    Matthew Wright
  • cow_ranchercow_rancher Solar Expert Posts: 112 ✭✭✭
    I think what you really need is a breather valve, because it must go both ways, typically just a "U" shaped plumbing fitting with perhaps copper wool then a layer of cotton and another layer of copper wool (or stainless wool, something that won't rust), would do what you want it to do.

  • mike95490mike95490 Solar Expert Posts: 8,166 ✭✭✭✭✭
    I use brass wool, from a Marine Supply store at a boat yard.
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  • animattanimatt Solar Expert Posts: 294 ✭✭✭
    i usually don't have an issue once people point me in the right direction.  but the breather valve not having much luck other than industrial type valves. not a big deal. if you have a moment a link would be wonderful.

  • cow_ranchercow_rancher Solar Expert Posts: 112 ✭✭✭

    I'm sure they make them in bigger sizes.

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