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Any Civil Engineering/Physics goats to answer a Q. about water pumping?

submitted by paul_neri to AskUpgoat 3.3 yearsMar 8, 2022 02:34:35 ago (+4/-0)     (AskUpgoat)

My cellar is flooding because there's been a lot of rain about. I've got a small pump (see Pic 1). Initially I used a very long hose attached to the pump (see Pic 2). The hose was laid out in a series of "s bends" down the yard which is on an incline i.e. the hose was not laid out straight.

The plume of water that emerged was about 6 inches long. As the pumping was taking a very long time I thought the hose might be slowing the water flow down due to all the s bends. So I replaced the long hose with a much shorter hose that could be laid straight down the yard and the effect was dramatic in terms of the length of the water plume (see Pic 3). Indeed initially the plume shot at for about 6 feet. A lot longer than the plume in the pic. In any event the plume in the pic from the shorter, straight hose, is still about 4 times longer than the plume from the long hose.

Ok. Now here is the conundrum. I thought I'd cracked the big time and my cellar would drain twice as fast with the different hose set up - it didn't or at least didn't seem to. So what I can't figure out is why a lot more water came out using the short hose compared to the long hose but ultimately the rate at which the cellar was emptied seemed the same.

My thought was that the long hose acted as a "dam" into which the water was fed at the same rate as with the shorter hose but as the water pressure diminished due to the s bends it was discharged at a smaller quantity but essentially the same amount of water entered both hoses and at the same rate but got discharged quicker from the short hose instead of being "stored" in the longer hose?


Pic 1

https://i.ibb.co/DRrRd4x/pump.jpg

Pic 2

https://i.ibb.co/rcFJvLs/long-hose.jpg

Pic 3

https://i.ibb.co/CmNgjwF/hose-plume.jpg



16 comments block

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[ - ] localsal 3 points 3.3 yearsMar 8, 2022 02:43:40 ago (+3/-0)

The resistance to water flow is proportional to the length of the pipe/hose.

The shorter the hose, the less resistance, the greater the flow.

The water table may be very high due to the rain, and the ground could be very saturated. You a) could be pumping the water out, only to have it be absorbed back into the water table, making you pump it out again, or b) the water table is high enough that you will have to pump everything below the level of the cellar before you are done.

A lot depends on the ground conditions, makeup of the soil, etc to determine how much pumping will actually be needed.

Make sure to send the water far enough away so it doesn't have a chance to get back to the cellar.

[ - ] paul_neri [op] 0 points 3.3 yearsMar 8, 2022 02:58:42 ago (+0/-0)

Thanks. So you're saying I'm imagining that the cellar isn't emptying quicker with the shorter hose length? And I could well be.

[ - ] localsal 1 point 3.3 yearsMar 8, 2022 03:04:21 ago (+1/-0)

Water table is like a very very large bucket - think swimming pool.

You are scooping the water out with a teaspoon, so as you scoop it away, the rest of the pool water rushes in to keep the water level.

If the soil is saturated, that could be days worth of pumping.

You could be imagining it, or it could be dropping by 1mm/hr, etc. Something very hard to tell.

[ - ] paul_neri [op] 0 points 3.3 yearsMar 8, 2022 03:12:02 ago (+0/-0)

Yes I didn't think about the "replacement factor".It could be re-filling quicker - it is certainly re-filling.Thanks again.

[ - ] observation1 1 point 3.3 yearsMar 8, 2022 03:16:29 ago (+1/-0)

If you can make sure the end of the hose is physically lower than the water being pumped it will all drain out in a siphon.

That might be hard to do in a basement but think down a driveway or into some other place outside

[ - ] paul_neri [op] 0 points 3.3 yearsMar 8, 2022 03:23:52 ago (+0/-0)

Ok, thanks. The problem would seem to be getting the water (in the hose) up a few steps first before winding the hose down the hill where it would be lower than the water being pumped.

[ - ] observation1 1 point 3.3 yearsMar 8, 2022 03:29:07 ago (+1/-0)

The pump might get it started. Once its going then it wont stop.

If pump can't do it (and I'd be surprised if it can't) then there is a way to do it without a pump

https://yewtu.be/watch?v=ZUsTT_RUEdQ&t=2m40s

[ - ] paul_neri [op] 1 point 3.3 yearsMar 8, 2022 03:41:27 ago (+1/-0)

Impressive. Food for thought. I'll experiment. If I could get it to work be like having two pumps going. Thanks.

[ - ] observation1 1 point 3.3 yearsMar 8, 2022 03:44:03 ago (+1/-0)

If going with the latter method remember to pour the bucket in at the apex

[ - ] paul_neri [op] 0 points 3.3 yearsMar 8, 2022 04:15:31 ago (+0/-0)

I'll try the former method (kickstart with the pump). I don't have the materials for method 2. My cellar only floods when there's a "biblical downpour" (170mm or above). Thanks.

[ - ] paul_neri [op] 1 point 3.3 yearsMar 9, 2022 02:19:04 ago (+1/-0)*

Worked a treat! What can I say? Quite remarkable. I was sceptical and feeling a bit lazy but I thought I have nothing to lose by giving it a go. So here is what happened blow-by-blow and with some pics:

1. reeled out the long hose and ran it out of the yard and down the incline in the adjacent public reserve aka the swamp:

https://i.ibb.co/c25cbfw/siphon-hose-4.jpg

2. I hooked up the hose to the pump and gave it a run and checked water was coming out.

3. I then detached the hose from the pump as quickly as possible and stuck my finger in the hose end to keep the suction and then I lay the hose end in the water:

https://i.ibb.co/dtQh7Ft/siphon-hose-1.jpg

4. I then waited a while to let the "electric pump water" in the hose drain away and checked out what was happening and didn't I get a pleasant surprise:

https://i.ibb.co/W5MPzvH/siphon-hose-3.jpg
https://i.ibb.co/GJM4XGV/siphon-hose-5.jpg

5. I checked regularly during the course of pumping to see if water was still coming out from the siphon hose and it was.

So I had the electric pump going with the shorter hose:

https://i.ibb.co/rfJTGR2/short-hose.jpg

and I had the "gravity pump" (siphon hose) going as well and I got rid of the water a lot quicker than on previous days due to...shorter hose for the electric pump (the long hose was a mistake) and the siphon hose.

Now what really bugs me is that if I'd known about the siphon hose I could have left it going all night and provided it didn't get clogged I would have got up in the morning to at least a significantly reduced water load compared to the previous days.But now I know , thanks to you,and while I'll upgrade my pump if it breaks down I'll still always use the siphon hose. Next time you're at the pub shout yourself a beer at my expense. Many thanks for taking the time to get involved with the issue.

PS

And another plus for the siphon hose is that it can be used in very shallow water unlike the electric pump. In the end I was using the siphon hose end like a vacuum cleaner in the remaining slops! I was surprised at how powerful the suction pressure was.

[ - ] observation1 0 points 3.3 yearsMar 10, 2022 12:39:22 ago (+0/-0)

Glad that finally worked out. Thanks for photos. Beautiful space you have there. Now that money saved on another pump might be better used on a dehumidifier!

[ - ] Silverfuck 0 points 3.3 yearsMar 8, 2022 08:20:03 ago (+0/-0)

You have a couple of issues here.

First, your pump is very small. It is probably only capable of pumping maybe 10-20 GPM (40-80 litres/minute). The maximum flow it will produce depends on the head required in the system (see below).

Second, your hose is small diameter. When water flows through the hose it creates what is known as friction loss: The water slows as it goes through the hose and rubs against the inside diameter of the hose.

Pumps are rated on flow and head (head is the pressure it produces and is measured in feet or meters usually). When the head in the system goes up (i.e. more pressure loss through the hose) the flow it will produce goes down. That is why the shorter hose allows you to get more flow, there's less pressure drop/friction loss in the shorter hose. A larger diameter hose will produce less friction loss as well. Both the shorter hose and a larger diameter hose will increase the flow.

Third, the sump (the hole) the pump sits in is not low enough. Typically a sump will sit several feet below the grade of the floor. This allows the water to drain and accumulate in the sump at a greater level, say a few feet of water. The higher level of water keeps the pump submerged in the water which cools the motor of the pump (the top of the pump in this case). You'll see in your pictures that the top of your pump is not submerged. I can guarantee that pump is getting super hot and will trip out when the temperature gets too high and will not turn back on until it cools or just burn out completely. Submersible pumps like this need the water to cool the motor. You can direct some of the water from the pump's discharge line on to the top of the motor to help cool it but a deeper sump would be better.

Also, your pump's suction (the bottom) is probably sucking in some air as the water on the floor gets lower. Air in the system can stall out the pump so it stops pumping altogether. The pump is running and getting hot but not moving any water.

Fourth, your float switch is not working as it should (the red thing at the top of the pump picture). It appears to be tied to the cord and is sitting way above the pump. The float switch turns the pump on/off as the water level rises/falls. In this situation your sump is not deep enough so the float switch is useless. It should be sitting on top of the water.

Good luck and keep us posted on your progress.

[ - ] paul_neri [op] 1 point 3.3 yearsMar 9, 2022 02:38:22 ago (+1/-0)

Some positive news.A goat called Observation1 suggested I try siphoning the water off by taking advantage of the incline in the back yard and it worked very well! So I had the electric pump going with a much shorter hose and the siphon hose going too and I emptied the cellar of water a lot quicker than on previous days. Yes my pump is probably too small but now I know about the siphon method I can get that set up at night and hopefully get up to a drained cellar! Thanks again for your interest.

[ - ] paul_neri [op] 0 points 3.3 yearsMar 8, 2022 17:51:24 ago (+0/-0)

Thanks bro. My response:

"your pump is very small."

Yes and if it breaks I'll upgrade to a more powerful model and find out about a hose with a larger diameter. The pump does do its job in the end it's just I feel the need to babysit it in case it/hose gets clogged with debris.

"the sump (the hole) the pump sits in is not low enough"

Yes I twigged to this and will consult my neighbour (a tradie) about digging out a hole.I'm not a very competent DIYer. Presumably I'll hit reinforcing in the concrete.Hopefully nothing else.

"pump is getting super hot" "need the water to cool the motor."

I didn't realise this. Ironically I've been trying to keep water away from its motor in case there was an electrical leak and I'd be zapped!

"float switch is not working as it should"

True but I'm not sure this would be an issue. The man in Bunnings (HomeDepot) told me to simply keep the float switch up by some means at a higher level than the pump.

Anyway...thankfully I only have this issue maybe once a year but I'm astounded at how much water gets in and how long it takes to get rid of it. Cellar area is the size of a small bedroom and the water can get to knee level.

So...off to hopefully do my last pump-out as the rain has stopped.

Many thanks.





[ - ] diggernicks 0 points 3.3 yearsMar 8, 2022 09:36:51 ago (+0/-0)

Lol

Ausfailia