Why didn't this water drain properly?

[Alex Franke]

Finally we got enough rain to fill my new rain barrel! Woohoo! Problem is that it overflowed and I don't know why...

The barrel is at the back of the house. It's about 4' high and it has an overflow hose connection near the top, but not right at the top. I connected a 50-ft hose to this and ran it off -- mostly down hill -- toward the wooded area in the front of the house.

When I went out to check on it tonight, the barrel was filled to the brim and spilling over and nothing was coming out of the hose. No part of the hose was higher than the overflowing water. The highest part of the hose was about 3-4 inches below where the water was spilling over, so I thought that gravity would just take the water out down to the level where it exits the barrel. Not so, apparently.

So I went to the end of the hose, put my mouth up to it, took a beep breath in, and then dropped the hose and it started to drain properly - down to where it was supposed to.

So it was like a siphon, but I don't know why I had to get it started.

Any ideas?

[chopnhack]

I would think that the resistance of the air in the long hose had something to do with it. Maybe a port lower down on the barrel will provide you with better results- that way there is more water pressure pushing down.

[Alex Franke]

Thinking about this a bit more... Here's a diagram and a physics question.

If when the water reached the drain it started filling the hose, is it possible that it fell into the low point and then trapped a bubble between the low point and the drain that -- with the water that already fell into the hose -- pushed back with more pressure than the water in the barrel above the drain?

Pardon my terrible MS Paint artwork.

[mschrank]

So I went to the end of the hose, put my mouth up to it, took a beep breath in, and then dropped the hose and it started to drain properly - down to where it was supposed to.

Any ideas?

Well duh! Obviously there was a small dead mouse stuck inside the hose. When you sucked it out and swallowed it, you released the blockage.

[LCHIEN]

if the highest part of the hose was 3-4" below the top of the water in the barrel as you stated, you only have 3-4" water head to get over that hump, assuming the hose was initially empty. You may have had more than 3-4" of pressure loss in the 50-feet of hose that the "head" could not overcome.

Once you sucked on the end and added to the natural head, water started to flow. The hose downhill of the hump was full of water and the suction of it falling added to the normal head, as in a siphon system.

anyway, that's my theory. It's either that or believe the dead mouse in your mouth theory.

[jackellis]

I think Loring's got it right. Get rid of the hump.

[JR]

I think Loring's got it right. Get rid of the hump.

No, no, no, no! There will be no simple solutions! Here are two solutions, each more elegant in its own way:

1. Use a sump pump with a float valve actuator. It's a power tool.
2. I'm sure in certain part of town can be found a woman, looking for work, and unuquely suited the task at hand.

JR

[Crash2510]

i am pretty sure you need more water above the hump to push however much is in it kind of like a trap in a sink

i would suggest drilling the hole in the barrel at least half way down

[LCHIEN]

i am pretty sure you need more water above the hump to push however much is in it kind of like a trap in a sink

i would suggest drilling the hole in the barrel at least half way down

That won't increase the head any. The head is still dictated by the height of the hump and the top of the water. having the exit hole lower won't change either one of those.

[Crash2510]

That won't increase the head any. The head is still dictated by the height of the hump and the top of the water. having the exit hole lower won't change either one of those.

loring I am still pretty sure that you have more pressure coming from the bottom of the barrel than you do from the top not sure although if this is enough to overcome the pressure of the hump

if you treat the drum like a toilet tank and the hump like the bowl the drum may reach enough pressure to flush but not sure in this situation

If you do a simple experiment like drilling 3 holes in the top middle and bottom of a column of water the water will shoot farther from the bottom hole because its under more head pressure. This is how a toilet works.

not sure if this would work in this scenario though maybe I just need more explanation

[eccentrictinkerer]

If you drill the hole at lower position, it will give you more pressure.

It will also drain your barrel.

edit: On further reflection, I think that drilling a hole lower won't change much. The difference in elevation (between the outlet and the highest point of the hump) is just too small. That and friction are the culprit.

[Crash2510]

If you drill the hole at lower position, it will give you more pressure.

It will also drain your barrel.

correct you are sir

kind of defeats the purpose

[eccentrictinkerer]

double post

[jackellis]

What's important is the different in elevation between the top of the water level and bottom end of the hose...unless the hump was high enough to create the same effect as a sink trap. That's why it takes less effort to refill a water tower by pumping up through the bottom of the tank (which is more typical) rather than putting the fill outlet near the top of the tank. If you fill from the top of the tank, the amount of work expended by the pump is guaranteed to be greater than if you pumped up from the bottom because you have to lift the water higher.

Makes my head hurt to remember this stuff.

[LCHIEN]

if you drill the hole lower in the side of the barrel the pressure at the new hole is larger than at the old hole. But, you use up all that extra pressure getting back up to the hump so it all gets cancelled out in trying to overcome the hump.
won't work a bit better.