Fixing The Pump: CR4 Challenge (04/08/08)

He might have just kicked more hose down the drain, except it says he fixed the situation after returning to the basement.

John was gone for only a minute. This tells us that whatever he needed was close at hand.

He might have gone to retreive a tool. He either searched for the tool amongst the items that would normally be present in Tom's house or he went to his car to get the tool. Then he used the tool to make an adjustment to the pump.

Or John went to retrieve some PVC pipe to replace the hose. The pipe might present less resistance than the hose to the pump, and allow it to operate more efficiently.

I agree CSM. Although, I think he would have used a kitchen knife to cut a garden hose

Yeah, mom would have reintroduced me to a razor strop fo that, but now you've introduced the fact that the hose is no longer long enough to reach the weeping bed and the water is draining back into the substructure and possibly causing more damage as it is now a directed assault on the foundation structure instead of a generally spread and even one. Shorten the exhaust, lessen the dispersal.

OK, I concur; ya got there ahead of me with the same answer I'd have given. And almost did - decided to go back and read existing responses before typing in mine...

Upon going back and reading the problem again, I agree that shortening the discharge hose is the correct answer.

John got some drain cleaner from the kitchen to clear the pump head and line is what I would think.

As Tom lived off the grid, John had installed an extension lead running to a change over switch in Toms kitchen just in case his batteries went flat! John flicked the change over switch which gave the house and Toms pump sufficient power to operate under normal conditions!

As was mentioned in post #3 and #6, he retreived sissors or a knife and cut a length out of the hose. Although, I would have cut 16' out so that I could keep a foot of the discharge end "in" the drain.

I would even cut 18' of pipe and use the directed flow at outlet in the drain.

But if the drain backs up, you have the possibility of backflow siphoning water back to the sump. If Tom is cheap enough to use garden hose for a permanent drain line, he probably did not install a check valve.

And he possibly was not pleased with cutting a perfectly good 25" hose! But that will inprove pump performance. I agree with CSM.

Cut the hose so it is just long enough to reach the sump. Less resistance in line = higher flow for a given supply pressure.

I too agree with CSM. Cutting the extra length is what Tom must have done to reduce the losses to minimum possible

The interesting coment is that John went upstairs. I'm wondering if the amount of hose is a red herring. If the hose went out 8 ft from the house, that leaves 17 ft of hose to go into the sump repository. If it's 10 feet or 10000 feet of hose sitting in the repository (sump pit), that shouldn't make a difference in the flow rate of the sump. Therefore he had to make a change to the drainage accruing in the sump pit.

This is where I've lost it...unless John was able to divert a standard drain to a more direct wastewater outlet.

Just a thought, or I've missed something completely...not that that concideration is outside the norm (Gimme a beer, Sam).

I tend to agree that cutting the hose is questionable. One would only use a sump pump to lift water from a subterranean basement up to a higher level. So a sump that is 4 feet deep and the cellar floor that is 8 feet under ground and the drain that is 8 feet outside the house. We have pretty much consumed the whole standard 25 foot garden hose length to meet the required run.

So he did not cut the hose. Instead I think he went up stairs and got the 1 inch hose from the back yard, and replaced the 0.5 inch hose that was connected to the pump and replaced it. The larger hose will provide for much greater reduction in loses than shortening a hose.

The problem with that theory is now the pump has to work harder against the increased weight of the water because the hose now holds more volume vertically.

Avery Montembeault

Wrong. Pump is working against pressure, not volume of water. The pressure of 8' of water is the same whether in a 1/2", 1" orr 10" hose.

Length of hose does matter. Total friction is proportional to length of hose. Longer hose sill cause higher friction for the pump to over come. A 1000 foot hose has 100 times the friction of a 10 foot hose.

No No you are mixing up volume and head. The head pressure will not change if he put in a much larger hose and greatly increased the volume. The pump will have to handle the friction & momentum changes for the larger mass volume however.

Hopefully we can assume that Tom did not have excessive hose outside his home since the area he is draining to is 8 feet away. The problem states that John went upstairs, not outside. John went upstairs and asked his wife to re-attach the gutter or move the sprinkler so the water runs away.

Tom went to get a knife to cut the garden hose at about eight feet or roughly 30% of the original. This should reduce the back pressure so John is happy. But hey... If John needs to buy a pump, I'll sell him one!

MF Lutz

John went upstairs to get his glasses. When he came back down, he saw that the pump wasn't plugged in. He just plugged it in.

All kidding aside, I'll go with shortening the hose.

I may be an idiot (no comment from the peanut gallery) but shortening the hose does not change the transitional lift. Basement height is a constant regardless of the length of the hose. Depth to sump is constant as well (ok, there's a pun there, but ain't had enough to drink to call it).

The length of drain is irrelevant. It's the rise and flow rate that are relevant. I.E. how high it has to move and the volume that is being pumped. Since it's water, pressure is a matter of power used to pump it. Volume only changes on flow rate (0 compression).

Therefore, in his journey upstairs he either opened or closed a valve...

...That's my story and I'm sticking to it until utterly humiliated (which probably won't be the first time...this week.)

Question...not in any way stating theoretical or empirical knowledge here, but flow rate through 25' of 3/4 inch hose is no different than flow rate through 50' of 3/4 inch hose. To my way of thinking , there might only be a time differential to charge the extra length of hose, no difference to the actual flow rate.

Hence, same pump, same height difference, same flow rate regardless of output length with the same pump hp. I.E. a 6hp pump, pumping water up an 8' incline, with a 1/2" output vent would pump the same amount of water at the discharge point at 8' past the rise, as it would if it was 1" past the rise. Hence only the incline height would determine pump requirements. (all in absolute theory, with no gravitational or frictional considerations).

Therefore, he did one of two things, he reduced the input to the sump (reservoir) or increased the output of the pump (volume out). No other option seems relevant. Hence, since there was no inference of increasing the pump's capability (pressure) or increasing the hose diameter (volume), in some way he must have decreased the rate at which water was stored by the sump.

Hence, somehow, he went upstairs and turned something off that was adding to the sump storage. My bet...turned off a tap.

Very true, and while I understand it on a primal basis, I don't have the math or physics background to be able to explain it with the degree of certainty that you have or have produced. Issue is, I've never seen a (call it 1/3) volume drop over 8 feet of tubing in any sump pump application. It may be that optimal or maximum flow was never produced over the original setup, but it's just experience. Don't let that dissuade you though, most of the construction I've seen causes architects major epileptic seizures.

But having a building background, shortening the pipe leading to the drainage point is a no win situation. If the water from the sump is not lead off to a sufficient distance or into a proper weeping bed (drainage area or cistern enclosure), then it will leech back in and exacerbate your problem...difference between engineering solution and practical application.

I do realize practical application was not a parameter of this exercise. I thank you for the theoretical though, as I know the parameter's exist, I did not know what they were (nor will I remember them as to be able to apply them, but danged if I won't remember to look them up).

Excellent answer.

Great response! I mean if the guy is using a garden hose on a sump pump, what level of precision is needed?

Let's look at the context, and move on. Kill this post please!!!

The reason tomkaighin has never experienced a decrease in flow based on length of hose in his "construction experience" is because he's most likely had a pump that was WAY OVERRATED for the amount of water he was wanting to move. Therefore a hose short or long didn't matter much because the pump had plenty of power to force the maximum volume of water through the hose period. If on one of his construction projects he had tried using a wimpy gold fish pond pump (one that barely lifted the water into the hose for expelling) he might have discovered that the length of hose attached to the pump greatly affected how much volume he was able to pump per hour. I'm going with shortening the hose. The exact length to be determined by the circumstances at hand.

I do like your comment on removing bends or kinks in the hose, since that can make a difference. However I will stick with the knife theory.

I will give you a vote for good answer.

No tom.

You conduct an experiment: Put about two Kms of pipe to same pump. No other change in situation. Same elavation, same suction height. Due to long pipe length, the frictional losses will go up and you will see no discharge of water, even though pump is running, however long you wait for discharge to start.

It has been quite some time since I lived up north where basements and sump pumps are common place. I wrote earlier that he went upstairs and brought a pair of scissors and cut the hose but after reading your analytical overview of the problem depending on what type of pump was being used he might have adjusted the float or even reset the breaker as it may have been out of adjustment or even stuck thus over running the pump and knocking the breaker off. Their are a few unknowns and variables of what might have or what could have caused this incident. Their is not enough information for me to correctly answer this problem. Gary Karm out...

Got a knife or sissors to shorten the hose to 9' reducing the headpressure by 16'. Almost two-thirds, increasing the flow rate.

P.S. I looked at no other answers before submitting mine. #3 has the problem of shortening the hose to eight feet not leaving enough hose to be attached to the pump underwater and spanning the 8' to the drain.

cut the hose to approx 9ft.

Everybody seems to like cutting the hose. My money's on John's having a larger-diameter hose up the stairs in the garage. :)

The tubing length will change the discharge rate due to the resistance, but I have another thought since my last post as I have read it a few more times.

I noted it does not say 'drain field' but says 'drain'. Evidently the drain is somehow and likely unintentionally connected to or just too close to the drain tile or inlet of the sump basin.

Another possibility, Stuck the extra length of hose down the drain so the whole system acts as a syphon. ffeJ

Yup. John went upstairs to retrieve a screwdriver to remove the screen over the drain, so the hose could be run down it.

ffei,

I absolutely agree. With the syphon action assisting the pump, the head pressure on the pump is reduced, thereby allowing an increase in pump throughput.

I also agree. The syphon action will speed up the drainage.

The reason the problem was fixed when he returned is simple -- if you assume he had turned the pump off before going upstairs, he had to turn the pump back on when he returned.

See comment 56. Sticking a discharge hose down into a drain is frowned upon by plumbing code officials due to the possibility of backflow siphoning back into the building.

Dear sirs: from the 1st, answer, this is the only one who considered increasing the flow by using some form of additional suction at output. ( if this output drain is common to the house sewer drian, I humbley suggest, He flushed the UPSTAIRS TOILET, which as it rushes by the end of the Sump OUTPUT Hose creates INCREASED SUCTION & thus inceases the pump output.) Retired Cottage Owner that regularily delt with sump pumps, septic tanks & some Dry seasons where the septic flow was the only flow, and reduced pump pressure almost stopped pump output. Carl.Guest.

john shortened the hose!

could have also straightened the hose as much as possible, as a bent hose (or the one jammed under the door to get outside) also causes flow restrictions.

Could have opened the door off the hose too.

John cut the hose pipe down to be just long enough to reach the drain thereby reducing the resistance by approximately 2/3rds andf depending on the pump curve the flow could increase by 25-30%

CUT THE HOSE TO A DECENT SIZE - REDUCES DRAG. REDUCES CHANCES OF AIRLOCKS

John told the dog to stop standing on the hose!!!!!!

Two things that Tom could have done from a fluid mechanics point of view, I don't know if the 1 minute mentioned in the question is sufficient

1. Put a reverse nozzle at the exit of the pipe to diffuse the flow and thereby reduce the velocity of the jet at the exit and therefore the energy lost in the jet at the exit. This would reduce pumping loss and probably impact head loss more significantly

2. Reduce the length of the pipe to reduce the losses

You folks are missing something from the question. Firstly the sump is shallow, as in not deep, which means that the drain is not in the basement. There is no reason what so ever to have a sump pump in the case with the drain at the same level, just connect the drainage to the sump directly to the drain. This eliminates the pump.

Instread the drain has to be outside the house some where and if they cut the garden hose inside, there would be no way to reconnect the hose back onto the pump. The obvious deduction is they did not cut the hose. If he cut the hose he would have had to do that outside and this does not fit the wording of the question which says he came back down and fixed the problem.

I like the idea that John tossed the larger hose into the window and came back down and connected it into the pump. The other possibility is John disassembled the pump and cleaned the buildup out to get better efficiency out of the system. Actually this seams likely as Tom has used this pump for a while and just recently has noticed its performance dropping off.

When he went upstairs he took one end of the hose outside away from the house and let the water drain down the driveway.

Cut the hose down to 8 ft long.

The frictional value of pipe is the Reynolds number. It is used to convert feet of pipe (and length equivilent for bends and fittings) ) so that the wall fricion can be calculated for hydrodynamics (water supply systems, hydronic heating, fire sprinklers, transcontinental pipelines, storm sewers, even river flows. X feet of conduit equals Y feet of friction head loss to the system.

He may have inserted a coil spring into the hose at the sump edge to prevent the kink, slipped a bent conduit elbow over the hose for the same goal, or to make the system legal, he might just have thrown the end of the hose out the window so that the sump field or city sewer was not taking storm water which are both illegal and/or stupid. The flooded septic field would be draining back to the house foundation drain, causing his sump water to turn green and smelly and plugging the system with algae. A bottle of bleach in the sump would have killed the algea and cleared the clogging hose and pump inlet, and a couple of years of chlorine tablets would have ended the organics of his septic overflow, and would only gave destroyed a half dozen pumps.

A similar reinforced down bend at the drain to a couple of inches above the p-trap at the floor drain would reduce the head depending upon the depth of his soil pipe in an emergency, but get the pump discharge into the storm sewer where it belongs, not into the sanitary system.

RichH

Noscifi used a lot of ink to say nothing. The problem failed to include info that could have made a significant difference. The only info provided offered a single solution. "Reduce the friction"!.

Had the info provided the angle rise to the discharge end of the hose there would have been another option. By laying the hose on a plank or other simularly used thing the angle of the rise could have been considered to also reduce the lifting effort. It is much easier to push a liquid up hill than lift it straight up.

Another consideration would have been to cut the hose at 16 ft. and to have used the length of hose that extended beyond the 8' rise to fall quickly downward, thus creating suction. Gravity adding to the pull increases the weight of the water that was now falling. All of the above would increase the efficiency of the pump by reducing the ultimate head pressure on the impeller.

toomuchfun

The first paragraph is correct. However, for a siphon to work over a hill or hump, the discharge opening must be lower than the source of water.

the discharge opening must be lower than the source of water

Where does it say it can't be ? Aslo, suck some coke up with a straw, then pull the straw clear of the glass with your tongue covering the end - the coke stays in the straw. Strangely enough, this works with the tongue held in the cheek. There's no problem to solve anyway, the detail given sucks enough on it's own !

Actually the siphon effect works to reduce the back pressure on the pump. The centrifical pump will deliver it's maximum flow with no back pressure at the pump discharge nozzle. As the back pressure increases the flow drops, so the siphon is legitimate. This is the whole reasoning behind the suggestions for cutting the hose, using larger hoses, etc.

Now if the pump is positive displacement, which could be the case, these arguments all fall through. Seeing as the problem does not specify the type of pump, the arguments need to be made for whether the pump is or is not a possitive displacement type.

Rick,

You are correct in assuming it could be a positive displacement pump since the original post didn't even state that is was a sump pump - just a pump.

However, assuming it is a positive displacement pump, you would also have to assume that the motor is undersized for the pump. If it is sized correctly for the pump capacity, there is very little that can prevent the pump from delivering it's full capacity. Even dead heading the output could possibly burst the hose or it could just stall the motor and it would trip out on overload. A restriction in the outlet of a positive displacement pump would result in the output pressure increasing to maintain the volume constant. Of course we really don't know anything about the pump, motor, or bursting strength of the hose.

However, it certainly has created a lot of discussion and one can only guess at how much corporate time/money has gone into this discussion.

You're quite right - he could form a syphon by dangling that extra hose down to a lower level. Maybe kick it down a drain or something, I'm sure I read that somewhere. Likewise, cutting the hose to reduce frictional resistance is brilliantly inovative. I'd never have thought of that. Not being told in any meaningful sense where the drain is, or even where the excess hose lies, leaves the whole thing somewhat open to speculation. How about the water powered pump I mentioned ? They might be screwed if the water companies power is out and they have no supply, but ya never know.

You are correct about the lack of enough information to find an appropriate solution. However: regarding the head and lift issue. Earlier in my construction life I owned a concrete pump. Concrete is considered a liquid until it hydrates. Hardens. We found that it was much easier, faster and more effective to lay the pumping pipe on a slope than stand it vertically. Regarding the falling water issue I suggest that you take a short piece of hose and use it to drain a barrel full of water. If the hose is 5/8 th inch Id then the flow of the water will be 5/8ths Od. Regarding the maximum head of lift. This is greatly dependant on the tolerances with the impeller to case and the power of the driving motor.

Toomuchfun

I'm not sure what you describe in the barrel comparison, but I'll get a barrel of beer to test when the 'answer' to this question is announced.

I'll chip in on that...

And obviously you have no need to understand that the bend type and length of conduit can be determined without any great trouble. Each of the 2 kinked bends in the hose probably has a length equivalent of 50 feet of hose. Shape the bends and the result will be better than cutting the length of the hose. Of course, the coiled hose also increases the equivalent length by another 50 feet, but according to some, there is no such thing as friction, so I guess we both have a lot to learn.

RichH

Since the sump & drain are only 8 feet away and the sump is in the basement I would assume the drain is also in the basement. Hopefully the drain is connected to a sewer or a line that exits the house are and not back into the sump.

If you only need 10 feet of hose (1 foot into sump+8 feet beteween drain & sump+1 foot into drain=10 feet) I would cut the hose to 10 feet. Thus reducing the back pressure on the pump.

Reduce the length of hose.Don't need 25 ft when the drain is only 8 ft away.

Increase the hose size.

These two wil reduce the head and thus increase the flow

He simply placed a small object below the pump legs to lift it from the bottom of the well. THIS ALLOWED FOR A BETTER FLOW OF WATER IN THE SUCTION PORT. Most of the sump pumps capacity collapse quickly with a restriction on the suction side.

Another good answer!

There was no information provided that would indicate that the pump inlet was restricted to less than the pumps capacity.

Cut off the excess length of hose.

John cut the hose down to 8ft, decreasing the flow resistance from pipe friction by over 2/3rds.

I think he cut off about 16 ft of the hose so there would be less friction.

I agree with CMS Engineer

Cut off the hose just long enough so that the end could be pushed down the drain to a level below the bottom of the sump. Reducing flow restrictions due to length and using siphoning action to over come some of the water colunm pressure on the pump.

I don't know about anything about water physics. So, I'll say he flushed the toilet.

John went out into the garden, retrieved a brick, went back into the basement, placed brick under hose closest to pump output. This raised the hose on the pump end which creates a downward siphon effect toward the drain & therefore increases the output flow. That's funny......

I think he went upstairs and turned off the water to the bath which someone had forgotten, putting too much water in the sump!!

...and thats my 2 pennoth!!!

As the drain is only 8 feet away from the pump and pump is attached with 25 feet long hose which is not required and posing unnecessary friction to the pump discharging less water. John goes to the drain and cuts the hose ,leaving only 8 feet connected to the pump thus the pump starts discharging more water.

Thanks

I think he went to get a sizzors or sharp knife and cut the hose. Less distance for the pump to have to pump water through. He only had 8 feet to go to the drain, shorten the hose.

John disappears upstairs to the kitchen to turn off the electric oven that is at 400⁰C and bellowing out black smoke! He was going to surprise Tom with a roast chicken that he reverse engineered the week before! After opening the windows to hide the error of his ways, he grabs a 6 pack from the fridge and goes back down to the basement. After tossing Tom a beer, he picks up a knife. Tom turns to John and asks 'What are you going to do with that!' John replies 'I'm going to cut the hose!' Tom looks worried but is comforted by Johns calm words of wisdom 'Don't worry Tom we've got a nice bit of chicken in the oven!' After Tom opens his beer, he turns to John and says 'It's going to be another one of those weekends John!'

If it was working fine and now it is not then something has changed. There is no mention of the water being pumped up much height. It is going from a shallow sump into a drain.

Three things could have happened. The suction is plugged, the discharge is plugged (the hose has a kink in it) or excess water is going into the sump that does not need to go into the sump. You might cut the hose to eliminate the kinks but you don't have to go into all kinds of calculations for friction and flow rates since it workrd fine originally, or is that an assumption since it only says "the pump isn't working fast enough."

If on the other hand it has never quite run fast enough then shortning the hose to reduce friction would help or perhaps there is two settings for the pump or it can be wired diffrently to run faster.