Water Main Siphon

[SLOBuds]

Two years ago I laid water lines throughout my 10 acre parcel. The main line was 2" Schedule 40 PVC.

There are a few places where I have 'branches' from this main line, with 'T' fittings, that are reduced size. So, as an example, the mainline is 2" and the branch is 1". Some times these branches lose pressure when a valve is open farther down the main 2" line.

I'm not positive why this happens, but I imagine that (maybe) the larger diameter line is causing some type of siphon effect on the smaller line.

How do I fix this condition so that all my lines have pressure regardless of their diameter and regardless of having a valve open farther down the line?

Thanks

 

[EddieWalker]

What size meter do you have? or are you on a well?

It sounds like your supply for the 2 inch line isn't big enough to handle your one inch lines.

The other causes for loss of pressure is head and distance. Going up in size to two inch won't increase how much pressure you have. Running that line for a long distance will reduce the amount of pressure that you have. In cities, they have pumps to build the pressure back up for long runs.

If the pipes run uphill, they will lose pressure. There is a formula somewhere to figure this out, but just keep in mind that any upward change from where the meter is, to where the water comes out will result in less water pressure. A few feet is hardly noticable, but ten feet or more usually is. Some homes have noticably different water pressure from one level to the next. It usually depends on how much they have at the meter. 60 pounds is good for a house, but if you have 30 pounds, you might not realize that it's low until you add a second floor bathroom and the water barely comes out the faucet!!!

A water pressure gauge is pretty cheap at Lowes or any other store that sells sprinker stuff. It screws on the end of the spicket. You turn on the water and see what it reads. Do this at every spicket to get an idea of what you have. The gauge will tell you everything you need to know about your lines.

Eddie

 

[JB4310]

What's pressurizing the system? and is some of this system gravity dependent.

This thought came to mind, If you have fairly low pressure and your topography is such that those valves that are "further down the line" are in fact much lower than the branches that are losing pressure. That MIGHT have something to do with it, lower pressure, or even no pressure on a higher valve would be a symptom of that layout.

Also if those lower valves you mentioned are the full 2" that's the greater volume draw and that would lower pressure more than opening a 1" line. The volume difference between 1" and 2" is 4X, not 2X like the pipe size, so opening one 2" valve is equal to opening four 1" valves. Regardless of size, in general the more valves that are open, the less pressure each valve would have, so I don't think it's a siphon problem but more of just a pressure drop.

These observations are based on my general experience with water flow, but I have no hands on experience with irrigation system etc. I'm sure many here do though.

As far as how to "fix" that, you would either have to have booster pumps like Eddie mentioned or try and open those valves that are down the line a little less, keeping more pressure in the system.

JB.

 

[AlanB]

You make your main line a circle or loop doubling back on itself and feed your branches off the loop. To draw a word picture, start at your tank with a T, go off the right side of the T with the mainline, go all the way around your yard and return into the left side of the T.

Most folks don't care enough to justify the added expense, Growers and irrigation folks trying to get even metered amounts of water out of nozzles are where I have seen this done.

You will still have pressure drop issues depending on volume, topography etc. but it should make it consistent on your branches

 

[SLOBuds]

Thanks guys.

The source is well, but that's probably not what you're really asking. I pump from the well up to a holding tank on my parcel. From my holding tank, I pressurize to the parcel through a 1.5hp pump.

Yes, there is an elevation change DOWN, and then back up (it goes down a valley then back up on the other side). The change in elevation is probably 20-30 feet. And the pipe is running over 1000 feet.

I think that all of these worse cases are in play: yes, the down-line valves are 2"; yes, there is a valve that we open which is at the lowest part of the valley.

So ... I think you guys are just saying that my pump isn't moving enough water under certain conditions. I'll make plans for an additional pump to boost.

Thanks again.

Martin

 

[forgeblast]

What i did to have water at different places on my property was to bury pipe (the 3/4 black water pipe that the box stores have) to different places. It is connected to my outside faucet and i run air through it at the end of the year to clean it out so it will not burst in the winter.
I have had an issue where it will syphon water , but if you look in garden stores they sell anti-syphon attachments that go right on your faucet. i have a couple and they work great.