Leaf blower

[ggunn]

Actually, yes, I have done the experiment. If the hose is dead level except for a bit at the far end and totally full of water, I do not have to blow harder, I just have to wait patiently for a longer time for the water to start moving.
If the hose is on uneven ground, with ups and downs and air pockets along the way, then more pressure is needed. And we can discuss the physics behind that offline to avoid boring this Forum.

One illustration of this is that a water level can work regardless of how long the hose is. But the longer the hose, the slower the oscillations that happen whenever you move just one end. It is all a matter of time. If you are impatient, you can blow harder instead.

OK, consider this:

Lay down a 6' piece of 4" conduit next to a 600' piece of 4" conduit on a level plain and fill them with water. Put frictionless pistons in them to keep the water from running out on its own. Which one are you going to have to push harder on to get the water moving?

F=m*a. Pressure is force per unit area; the areas are the same so that cancels. There's a lot more mass in the long conduit, hence a lot more force is necessary for the same acceleration.

Granted, even a little force gives you *some* acceleration, but if you'll look a few posts back I said, "I think with a ton and a half of water to move ... with a leaf blower you'd have a long wait." I think that was accurate.

I'm still up for trying it if you want , but I don't think we are disagreeing on a fundamental level. I don't think either of us believes that a leaf blower is a practical solution. If nothing else, I believe that the back pressure would burn out the motor in the leaf blower long before the conduit was clear.

 

[hardworkingstiff]

I agree the leafblower won't cut it.

No one has mentioned that whatever is used, there is a good chance a lot of water will remain in the conduit. I bet the air will work its way above the water inside the conduit and will never get all the water out. How much will stay in the conduit I could not tell you , but I think it will be enough to be trouble when trying to get a rat through the conduit( if using a vacuum or blower).

I think you could get a rat through with a 185 CFM air compressor.

 

[James S.]

I have done this on a smaller scale. It was 3/4" pipe and I used an air compressor with a rubber tip something like this.

It worked great. I don't know if it would work on a 4" pipe but I don't think a leaf blower would be able to build up the pressure needed to move the water. With an air compressor you would be able to raise the psi and might stand a chance.

 

[eHunter]

It is not just about pressure alone, sufficient volume to have enough air velocity to displace the water will be required to remove the water in the conduit.
A 4 inch conduit will require a lot of air volume to transport all of the water out of the conduit.
A foam rat in good shape would help in "sweeping" the conduit.
We usually use a 100CFM compressor with a 1 inch hose to cleanout tubing over 3 inches with excellent results.
When we encounter mud and debris in conduit we use a portable pressure washer with a water jetter nozzle that works really good.

 

[cowboyjwc]

When we had this problem, we simply "mickey moused" a smaller hose to a big shop vac and sucked the water out. Always easier to pull a rope, than push a rope.

 

[69gp]

It all depends on what kind of blower your using (Gas or electric) and where you are using it to. If you are inside with a gas unit I would say your not going to use it.

I was doing a 4 story wooden frame apartment a few years back and my guys were working on the 3rd floor I was in the basement They came down complaining about the fumes. I went up there and one of the carpenters was cleaning the floors with a gas powered leaf blower. I told him to shut it off and not use it inside. He complained like a little girl that he can use it. After a few choice words he told me he was going to go talk with the super. well five minutes later he was back and told me the super said he could use it. DING DING DING I am ticked off now. I informed him in these exact words "you start that thing up im going to throw it out the window and if your holding onto it your going to". Needless to say he did not use it. Guy was such a dope. He wore a brim style hard hat with no harness support inside it, after that i wanted to teach him a little safety and hit him in the head with a 2x4 and see it the hard hat worked.

As for the super he got a little lecture on safety from me.

 

[kwired]

IMO what you are not considering is the inertia you have to overcome to get over 3000 lbs of water moving. Have you ever tried to blow the water out of a garden hose by mouth? The longer the hose, the harder it is.

C'mon, let's set up an experiment. I'll bring the leaf blower. You bring the 600' of 4" conduit. We can use my hose.

.

OK, consider this:

Lay down a 6' piece of 4" conduit next to a 600' piece of 4" conduit on a level plain and fill them with water. Put frictionless pistons in them to keep the water from running out on its own. Which one are you going to have to push harder on to get the water moving?

F=m*a. Pressure is force per unit area; the areas are the same so that cancels. There's a lot more mass in the long conduit, hence a lot more force is necessary for the same acceleration.

Granted, even a little force gives you *some* acceleration, but if you'll look a few posts back I said, "I think with a ton and a half of water to move ... with a leaf blower you'd have a long wait." I think that was accurate.

I'm still up for trying it if you want , but I don't think we are disagreeing on a fundamental level. I don't think either of us believes that a leaf blower is a practical solution. If nothing else, I believe that the back pressure would burn out the motor in the leaf blower long before the conduit was clear.

I don't claim to be a hydraulics or pneumatics expert, but it doesn't take all that much air pressure to lift a heavy object if you have a large enough "air pillow" underneath of it. Those "jumping pillows" that you see sometimes that the kids (and some adults) like to bounce on are quite capable of lifting a vehicle.

The hydraulic system that operates the brakes in your car only needs fairly light foot pressure compared to how much pressure is applied to the brake mechanism - even without additional power assistance in modern brake systems. Would you rather press the brake pedal in a vehicle with no power assistance or stick your feet through holes in the floor and try to stop that vehicle by dragging your feet on the ground?

If you have 4 inch pipe that is level and full of water and assume that the water somehow will not run out on its own then applying only one ounce of pressure will push the opposite end with the same one ounce of pressure. We are talking about a liquid that will have no friction compared to trying to move solid particles through same pipe. It will have some friction against the walls of the pipe.

What you need for pressure to evacuate this liquid is enough pressure to overcome the amount of lift necessary to raise it past the highest point of the containment (pipe) Applying pressure of one inch water column should lift the water level at the other end one inch regardless if you have a 1/2 inch pipe or a 4 inch pipe. In this case if you need to raise the water 30 inches before any will flow out the other end one inch of pressure will never get it done - again no matter what the pipe size is.

If you need to raise the water 30 inches before any will flow out the opposite end and you apply 31 inches of water column it will flow from other end, but not as fast as if you applied 100 inches of water column.

Now once you removed enough water that you have an air gap in the pipe you will need a much greater volume of air, or some kind of piston to keep a seal against the water or no more water will be coming out

ETA: another example like I mentioned above is think of how many thousands of pounds a truck may weigh, yet a tire with only 50 PSI of pressure holds it up.

 

[Smart $]

...

If you need to raise the water 30 inches before any will flow out the opposite end and you apply 31 inches of water column it will flow from other end, but not as fast as if you applied 100 inches of water column.

...

Not going to join anyone's debate... just providing some relevant info.

0.4335 psi = 1' H₂O
1 psi = 27.68" H₂O

Doesn't matter whether the pressure differential is by vacuum or compressor/blower, but the aforementioned figures are with respect to clean water and assuming an atmosperic pressure of 14.7 psia. The thing with vacuum is that it is limited to a max equivalent to negative atmospheric pressure (-14.7 psig or 0 psia).

Yes, inertia figures into it, but as GoldDigger mentioned, it is simply a matter of time (and continuous pressurization). High pressure from a compressor will get more water out, as it will continue to blow out water even after there's an air passage (although a supersucker would probably challenge that statement).

The other matter with using a normal wet vac is that at 3250 lbs of water, you'll have to empty around 390 gallons of water...
:slaphead:

If both ends are inside and water damage could occur, the best method to get the majority water out is a hose-in, hose-out portable pump. Put the extraction hose into the lower end, if there is one.

 

[kwired]

Not going to join anyone's debate... just providing some relevant info.

0.4335 psi = 1' H₂O
1 psi = 27.68" H₂O

Doesn't matter whether the pressure differential is by vacuum or compressor/blower, but the aforementioned figures are with respect to clean water and assuming an atmosperic pressure of 14.7 psia. The thing with vacuum is that it is limited to a max equivalent to negative atmospheric pressure (-14.7 psig or 0 psia).

Yes, inertia figures into it, but as GoldDigger mentioned, it is simply a matter of time (and continuous pressurization). High pressure from a compressor will get more water out, as it will continue to blow out water even after there's an air passage (although a supersucker would probably challenge that statement).

The other matter with using a normal wet vac is that at 3250 lbs of water, you'll have to empty around 390 gallons of water...
:slaphead:

If both ends are inside and water damage could occur, the best method to get the majority water out is a hose-in, hose-out portable pump. Put the extraction hose into the lower end, if there is one.

Even a siphon tube will work, and only pressure/vacuum involved there is limited by length of vertical drop in the siphon tube. It will likely take time though as the pressure and volume are both going to be low, plus the suction end must be in a low spot in the pipe to remove the maximum amount of water it is capable of.

 

[Hv&Lv]

Didn't take the time to read all the posts, but I blow string in 3 & 4" PVC all the time. sometimes with a leaf blower, and sometimes with an air compressor equipped with the proper attachment.
The leaf blower won't do the job. Sure you could time the blower to get the water to cycle and run out a little at a time, but it will never empty the pipe enough to blow a rat through. Get a large volume air compressor.

 

[mcelweec@gmail.com]

The greenlee 690 worked.