sump pump relief hole

[roofster]

Replacing my sump pump and some of the discharge PVC. They say to drill a relief hole between check valve and pump outlet to avoid air locking the pump. As long as the hole is in the pit, should it be above or below normal water level?

Found an answer, looks like decent forum too.

http://www.selfhelpforums.com/showthread.php?t=27049

 

[SCutchins]

Replacing my sump pump and some of the discharge PVC. They say to drill a relief hole between check valve and pump outlet to avoid air locking the pump. As long as the hole is in the pit, should it be above or below normal water level?

Found an answer, looks like decent forum too.

http://www.selfhelpforums.com/showthread.php?t=27049

My sump pump actually did get air lock a couple of years ago, I drilled a hole and it hasn't happened since. I drilled it below water level but I can't see how it would make a difference.

 

[KCarGuy]

That makes no sense...then why even have a Check Valve if you bleed it off all the way to the waterline?

 

[crewchief888]

That makes no sense...then why even have a Check Valve if you bleed it off all the way to the waterline?

kinda what i was thinking too.

 

[Heavy Metal Doctor]

That makes no sense...then why even have a Check Valve if you bleed it off all the way to the waterline?

not all the way -- the hole goes bellow the check valve....
.... and my understanding was that it allows air out for the pump itself which may otherwise keep the impeller from priming up and actually pumping.

 

[John in OH]

That makes no sense...then why even have a Check Valve if you bleed it off all the way to the waterline?

Yeah, I know. At first glance it doesn't make sense ... but it works.

I encountered the same problem many years ago ... sump pump wouldn't pump on a reliable basis. Drilled a 3/32" hole in the discharge pipe above the water line but below the check valve and it never gave another problem.

I angled the hole down so the water spraying from the hole was directed back down into the sump.

 

[alecmcmahon]

I have my check valve as low as possible, maybe 2 " above the discharge of the sump pump, then the hole in between that. I think my instructions called for a 3/32 hole as well. ( 1.25" discharge )

 

[nmanitou]

A relief hole can be useful because it allows the pump to purge entrapped air, but its usually only really needed for the first initial priming of the pump. If your pump continually loses prime, then the root problem may be setting the "off" float position too low.

PS - it will work best if located above the water line

 

[Frank The Plumber]

The answer to this is found in fluid hydraulics.

You are not drilling a hole in the pipe to relieve any form of air pressure.

You should drill this hole directly above the connection fitting at the pump base.

The principles of fluid dynamics are such that a liquid may act as a solid in a static position.
In this static position the fluid may be more prone to act as a solid if there should be added pressure.
Said pressure is exerted by the fluid column that is trapped between the pump outlet and weir of the drainage outlet.
In a case where the pump base sits in a 36" deep pit and exits to a pipe at 7 feet above floor the water column may be 10 feet. If you took that 10 feet and filled a bucket with it you may have 3 gallons of waterX 8 = 24 ponds of fluid pressure applied, calculate the check flap resistance into the equation and you may fluid lock a pump.

Thus by relieving the water column at the base of the pump you allow the pump to discharge unloaded and allow the velocity of this water discharge to lift the check and properly function.

Over the course of a pumps life this elimination of load may earn the pump a 5% capacity towards life and 5% power savings as most pumps elevate their power usage per the respected load applied.

 

[nmanitou]

Frank the plumber is technically correct, but if the condition he describes is occurring, then the simple fact is that your pump is not correctly sized. Every centrifugal pump has a performance curve that describes how much pressure it can overcome at various flow rates. If the pump needs a relief hole to start moving water - it is simply the wrong pump.

 

[Holedgr]

Frank the plumber is technically correct, but if the condition he describes is occurring, then the simple factz is that your pump is not correctly sized. Every centrifugal pump has a performance curve that describes how much pressure it can overcome at various flow rates. If the pump needs a relief hole to start moving water - it is simply the wrong pump.

I respectfully disagree. EVERY Zoeller pump I have installed recommends a relief hole. It does not "need" it, but with 3+ gallons of water to overcome when the pump starts, it certainly has proven to extend pump life.


-T

 

[Frank The Plumber]

Frank the plumber is technically correct, but if the condition he describes is occurring, then the simple fact is that your pump is not correctly sized. Every centrifugal pump has a performance curve that describes how much pressure it can overcome at various flow rates. If the pump needs a relief hole to start moving water - it is simply the wrong pump.

Every sump pump manufacturer specifically describes in their installation instructions that you are to use a relief hole when setting up the sump pump and or ejector pump.

While per your theory you may feel that you are correct you must also realize the limits within which a sup pump operates.

This performance curve you speak of is limited by available amps.
The average sump pump operates within a range of 7 to 14 amps.

If you were to size a sump pump per this recommended performance curve you would quickly have a pump that could not function correctly within the limits.
Therefore, given the fact that it is required and in most cases must be provided to ensure that the pump does not lock, it is done.

I have literally drilled hundreds of holes in piping to prevent lock on installations by people professional and non who have argued the drilling of the hole, the where and the why. I have been to court to present a statement as evidence as required in a case where a plumber did not drill the hole and was sued for a fortune in damages.
I took the stand and upon being asked a question presented the manufacturers installation guide to the judge.
I never had to say a word. The hole was even illustrated.And exact location shown.
Go read your guide.

 

[Frank The Plumber]

I respectfully disagree. EVERY Zoeller pump I have installed recommends a relief hole. It does not "need" it, but with 3+ gallons of water to overcome when the pump starts, it certainly has proven to extend pump life.


-T

Yup, The Zoeller has the illustration, I install about 120 Zoellers per year. About another 150 Hydromatics and another 50 or so Liberties. I get about 20 calls a year from people who think they need a new pump and Handy has not drilled the hole, I drill the hole for them and Handy gets displaced.

 

[68C10]

The hole being discussed is typically called a weep hole. It is drilled in the discharge pipe below the checkvalve. It's purpose is to provide a path to expel air that can get trapped in the pump housing and prevent the pump from priming and removing water from the pit. It is very good insurance to drill this hole any time you install a pump with a check valve whether or not you think the pump's impeller may lose it's prime. Floats can be adjusted perfectly but what about the sump pump that sits in a basement waiting to remove ground water that has not seen rain for months. Most likely the pit is dry and the air lock condition will occur on the next pump cycle. The problem is air lock, you need to remove the air from the pump and piping.

 

[roofster]

That makes no sense...then why even have a Check Valve if you bleed it off all the way to the waterline?

Check valve stops back flow from going into the pit.

Glad I started this thread, totally agree with the fluid dynamics post. Drilled my hole & mine is working fine, except the float needs adjusting. Coming on too much. My instructions are ****. Does not say a thing about adjusting. We got 3.5" of rain Wednesday, 1.25" today. That's are normal for May in 2 days. Supposed to let up and quit all together by Saturday, so I'll try to adjust the float this weekend. Basement is drying out, nothing got too wet except the floor

 

[nmanitou]

Exactly my point. These are small pumps limited by amp draw for a fractional horsepower 120V circuit. So, they have very low "shut off" head. Which means they can't overcome the static pressure of the discharge system - even at very low flows.

I design pumps for a living and understand the hydraulic properties of pumps. I'm not saying using a weep hole is wrong, just that it is a cheap way of getting a pump to work in a system it is really too small to perform in.

 

[68C10]

Sorry you're wrong the weep hole is there to evacuate air. It is not to get a pump to work in a system that it is to small for. The pump performance will not change with or without a weep hole. It will either work in the system or not; the weep hole prevents air lock. You have to size any pump correctly or it won't work. The pump has to overcome static head and friction head during pumping.

 

[fefarms]

Sorry you're wrong the weep hole is there to evacuate air. It is not to get a pump to work in a system that it is to small for. The pump performance will not change with or without a weep hole. It will either work in the system or not; the weep hole prevents air lock. You have to size any pump correctly or it won't work. The pump has to overcome static head and friction head during pumping.

+1

I agree with 68C10. The weep hole is for evacuating air and facilitating priming. Sump pumps are single rotor radial flow centrifugal pumps. They are not positive displacement and do not care if they have to start against the maximum design head. They are not limited by the "7 to 14 amp current draw", but rather by the pump curve of radial flow centrifugal pumps.

The power that they draw is the LEAST when they are "deadheaded" (the point at which flow drops to zero because there is too much head pressure to overcome"). Look at this reference from Gould pumps for a discussion:
http://www.gouldspumps.com/cpf_0009.html

 

[nmanitou]

Sorry you're wrong the weep hole is there to evacuate air. It is not to get a pump to work in a system that it is to small for. The pump performance will not change with or without a weep hole. It will either work in the system or not; the weep hole prevents air lock. You have to size any pump correctly or it won't work. The pump has to overcome static head and friction head during pumping.

See my post #8. I don't think we disagree.

 

[Frank The Plumber]

The market at this point will bear a pump cost og between $100 to $150 on a new sump pump. Ideally you may be correct about the pumps ability to over come the pressure, a larger force applied by a pump would do this. You cannot design your customer. Nor can you design your pumps operating environment.
In many a situation I will encounter multiple pumps on a 20 amp circuit.
An ejector 12 to 15 amps
a sump pump at 7 to 12
a battery back up system maybe another 5 to 7
often an alarm. another amp.
You tell the homeowner that they need another circuit and they argue even against all of the math, sorry but math rarely lies.
All they know is that this works now and I'm not calling an electrician.
So there you have the dilemma.
Now there are certainly more efficient pumps out there than the standard oil cannister junks we have been using, I often use a Glentronics unit in a battery draw situation such as from a sumppro unit to extend battery life, It is how ever a fine line design situation and you can't really get much more out of the situation, mostly due to lack of cooperation and system concept by the average home owner.
And so we have pumps which need holes in them.
And if you observe the system in action, you will see. That the system actually introduces air into the space between the check valve and pump base, this air space is not discharged into the water of the pit, it is forced through the check assembly with the remaining water as the pump operates. Thus the hole is there to lessen head and give the pump a chance to get a flowing stream of water hitting that check valve and punching open the remaining head pressure at the check valve.
Works much the same as this. You have a car with a ****** little engine, at 600 rpm if you gun it it's a total dog, but if you drop the clutch at 1800 you get a little taste of pep, or so you think. Think of it as a cheap stall converter for a cheap pump.

 

[68C10]

I guess we will agree to disagree but the problem is IF air gets in the pump chamber and surrounds the impeller it can prevent the pump from priming and pumping. The weep hole gives a place for the air to vent. It absolutely does not improve pump performance in actuality performance is actually lessened.
Shut off head is greater without the weep hole but the hole is required to prevent air lock.

 

[Frank The Plumber]

Both and or any lock. All kinds of weird **** can happen. BTW try those magic silencer check valves, they are very quiet, if the thunk bothers you, that's your ticket.

 

[HookWorse]

A quiet check valve??? When they installed my sewage pump, it sounds like a gun going off when the valve slams.

Where does one find one of these magic valves?

 

[diggerrick]

I've designed several sump systems for industrial use, and don't recall ever including relief holes or seeing them mentioned in the pump spec's. Maybe the pipe fitters took care of it themselves?

 

[Frank The Plumber]

On an industrial system you would have plenty of power. You would use a better quality more expensive pump or a self priming pump.
You should be able to find these check valves at a plumbing supply house.
Silent check, Magic check to name a few.
www.magicplastics.com

 

[Greatbear]

The need for the vent hole is dependent on the operating situation the pump faces. If yours is the type where your sump/basin will become dry below the intake of the pump during a dry spell, you need the vent. What will happen when water once again begins to fill the basin and there is no vent, you will have an air pocket in the impeller chamber or volute of the pump. This happens because the column of water and the closed check valve are too much of a resistance to allow the incoming water to push the air (and with it, the water) into the business end of the pump, leaving it unprimed.

The best demonstration is to take a drinking glass, invert it and set it in the bottom of a sink. Now start filling the sink with water. The glass will trap a pocket of air. If there were a tiny hole in the bottom (now top) of the glass, the air would easily escape and the glass would fill. With the sink full, tip the glass until the air bubbles out, and then invert the glass on the bottom of the sink again. Now, empty the sink. The glass will remain filled with water until the sink water level reaches the lip of the glass, once the air makes its way into the glass, it suddenly empties. This is what will happen to a sump pump that experiences a drop in water level below the intake. If the pump does not shut off before the water level gets too low, the same thing will happen, air will enter and the prime will be lost. Since a sump pump is a centrifugal turbine-style pump, it has no ability to pull a suction with air.

The old-school "pedestal" style pumps with an open motor mounted about three feet from the bottom business end of the pump have an internal vent, these don't need the magic hole below the check valve.

Note that the first time a submersible sump pump system is assembled, lacking the vent, it will perform perfectly and will continue to do so until either the pump is lifted above the water level or the water level falls below the intake. Once this happens, it's most likely the system will become air locked (and you'll have a flooded basement).

 

[68C10]

Greatbear is right. Like I said air lock.

 

[Patrick Bowman]

Thank you, Greatbear (and Mike the Plumber). I've spent way too much time trying to figure out whether this air lock thing is for real or just a superstition. I hate doing these things without knowing why. At last I understand exactly what the air lock phenomenon on sump pumps is!

And yes, I know I'm replying to a thread that's a couple of years old. I didn't need a sump pump then.

 

[DangerousDan55]

Here is my post from last month on this issue...

Re: Sump Pump Weep hole
Here is my angle on the vent.
With your vent hole located between the pump & disch check valve, it does not act as a anti- siphon. IF you didn't have a disch check valve in you line, you would need a vent hole drilled at a high point to prevent the siphon or back flow effect that would refill your sump.

I worked for Shell oil on pumps. BIG pumps! (retired)
On some of our Big sump pump, we had vents on the discharge side of the pump.
Follow me here....
The water is pumped out (or evaporated) to such a low level and air enters the pump. Later the sump recieves more water raising the sump level. The water level tries to enter the pump suction & the trapped air inside the pump is forced out the vent. So now the pump impeller is submerged in water, or we say it has a suction water supply.

Now, lets plug the vent hole!
Now after a low water level conditon & the pump impeller is dry, with air in the pump all the way up to the disch check valve. Now you recieve water into the sump. The level rises up to the pump suction. BUT, the air is now trapped inside the pump & disch pipe due to No vent. The water level can reach the top of the sump & the pump still cannot get rid of the air to alow the water reach the pump impeller. Let me say this is true for only a centrificul pump.

A no vent situation is just like when you have a kitchen sink full of water & then take a drinking glass, hold it upside down & lower it into the water. The air is trapped inside the glass!
Now imagine a pump impeller inside the glass. It Aint Pumpen!

So, as long as there is a vent, the water level inside the pump is Always the same as the level in the sump. Thus the pump has a suction supply.

The Pump Whisperer!

 

[M17715]

"THEY" say to drill a hole? Who says to drill a hole? Not all sump pumps get holes. If it didn't come with one, I wouldn't drill one in it. But if they pump upwards, I would put a check valve in the PVC going out.

 

[DangerousDan55]

"They" for one, is Myers pumps. Actually some Myers pumps already have a vent hole In the casing. But "They" also state that you could add a second vent hole as a back up in case the other vent hole plugs up.
It doesnt take much trouble to research the Net to find answers.

Persons could find out the Mfg & Google it.
The Pump Whisperer.

 

[proton777]

Is this thread still active? I have a similar problem and would like to add my circumstances to the discussion.

 

[roofster]

Go for it Proton, I got my answer a long time ago. Or start a new thread, up to you

 

[proton777]

Cool. I'm reading many issues I've been experiencing.

Using my existing pump, I had my 1 1/2" discharge PVC re-run and now have a few problems. New piping was installed from the pump in the basement, up above the ceiling, across the basement, then outside the house through the foundation. After the new pipe passes through the foundation, it meets up with the existing discharge pipe outside. A new cleanout valve outside joins the old pipe and new pipe.

There is serious pressure in the discharge line now. I know this because one of the connections inside the house has air hissing and a bit of water is leaking (a separate problem which will be fixed). When I unscrewed the cap on the cleanout valve outside, it was like opening a can of soda that had been shaken. A gusher of air and water. After the pump ran again, the pressure came back. I figured air lock. I added an air vent at the cleanout valve, which was simply a 2 feet piece of 1 1/2" PVC, screwed into the threads on the cleanout valve vertically where the cap was, then added a 180 "U" so nothing could get in.

Problem solved? Nope. The next time it rained, all the water being pumped out was now exiting via the "vent" I just added even though the path of the main pipe is down hill. This happened on several pump cycles. Obviously it must be a clogged discharge pipe down stream of the cleanout, right? Maybe not.

Thinking that was the case, I forced water down the discharge pipe at the cleanout valve with a garden hose for several minutes. There was no problem draining. It drained fine even with way more volume than would have been pumped on a normal cycle. If the discharge were blocked, enough water was sent down to the point where it would have backed up to where the hose was inserted.

So now what? For some reason, later in the day as the pump continues to operate, there is no longer any pressure in the discharge pipe. The pump ran 10 more times and I opened the cleanout valve cap after several pump cycles and there was virtually no trapped pressure. Negligible. So is the discharge really blocked?

If I simply had an air lock, the vent I added at the cleanout should have allowed the air to escape and gravity would guide the water to where it's supposed to go. Instead, water discharged through vent at full pressure. But if the discharge pipe were blocked further down, why is water flowing freely now?

A couple of other curiosities. Every forum I've read relating to this problem mentions drilling a hole in the pipe between the pump and check valve, but mine has no such hole. However, my Zoeller pump has a hole built right into the pump. I would like to know if this serves the same purpose as the hole everyone is drilling, or for something else, and if I should drill one in my pipe anyway.

Finally, when the pump shuts off, the discharge pipe coming vertically out of the pump and up to the ceiling bangs. I don't know if this is a relevant symptom or if it's just water slamming the check valve closed. Either way I'm concerned with something eventually breaking.

I'm at a loss as to what to do since my problems are inconsistent. A clogged pipe should stay clogged. My next move will probably be to call someone to snake the discharge line between the cleanout valve and the storm sewer and be 100% that's not the problem.

Thanks for any suggestions anyone can offer....Tony

 

[LS6 Tommy]

I design pumps for a living and understand the hydraulic properties of pumps. I'm not saying using a weep hole is wrong, just that it is a cheap way of getting a pump to work in a system it is really too small to perform in.

Sorry you're wrong the weep hole is there to evacuate air. It is not to get a pump to work in a system that it is to small for. The pump performance will not change with or without a weep hole. It will either work in the system or not; the weep hole prevents air lock. You have to size any pump correctly or it won't work. The pump has to overcome static head and friction head during pumping.

X2. 68C10 is correct. If the point of a weep hole between the pump discharge & the check valve is to help an undersized pump overcome the static head at startup to open the check valve, a weep hole would make it WORSE. The point of the weep hole is to purge entrapped air, just like the installation instructions on most every sump pump I've ever installed over the past 30 years indicates.

Tommy

 

[proton777]

I'm not sure what "overcome the static head" means. It's a Zoeller pump - not a cheap one - which has been in use for a few years. No problems as far as I could see before new piping was installed. The discharge pump comes out of the pump vertically about 8 feet, then it's all down hill from there.

I'm not taking sides since I don't know much about this, but here is the first FAQ on the Zoeller web site:

DO I NEED TO DRILL THE 3/16" (5 mm) VENT HOLE?
If a check valve is being used we recommend drilling a vent hole. This hole is located in the basin between the pump and check valve usually a few inches above the pump "on" level but below the pit cover. The vent hole will prevent air locking from occurring.

Confused.

 

[DangerousDan55]

Here is my angle on the vent.
With your vent hole located between the pump & disch check valve, it does not act as a anti- siphon. IF you didn't have a disch check valve in you line, you would need a vent hole drilled at a high point to prevent the siphon or back flow effect that would refill your sump.

I worked for Shell oil on pumps. BIG pumps! (retired)
On some of our Big sump pump, we had vents on the discharge side of the pump.*@#$
Follow me here....
The water is pumped out (or evaporated) to such a low level and air enters the pump. Later the sump recieves more water raising the sump level. The water level tries to enter the pump suction & the trapped air inside the pump is forced out the vent. So now the pump impeller is submerged in water, or we say it has a suction water supply.

Now, lets plug the vent hole!
Now after a low water level conditon & the pump impeller is dry, with air in the pump all the way up to the disch check valve. Now you recieve water into the sump. The level rises up to the pump suction. BUT, the air is now trapped inside the pump & disch pipe due to No vent. The water level can reach the top of the sump & the pump still cannot get rid of the air to alow the water reach the pump impeller. Let me say this is true for only a centrificul pump.

A no vent situation is just like when you have a kitchen sink full of water & then take a drinking glass(pump case), hold it upside down & lower it into the water. The air is trapped inside the glass! (Pump case)
Now imagine a pump impeller inside the glass. It Aint Pumpen!

So, as long as there is a vent, the water level inside the pump is Always there for the pump & has a suction supply.

The Pump Whisperer!

 

[G McKay]

I have seen pumps made both ways. But if the pump comes without a hole, I would not drill one in it. I would leave it the way it was designed.

 

[DangerousDan55]

Proton, you put the vent hole in the wrong location. The vent hole must be Below the discharge check valve. Not way outside at the clean out.
The discharge check valve is "a valve" that closes automatically. So this valve stays closed fairly tight until the running pump water pushes it open. When the pump is off the valve is closed *&* you get a low water level in your sump to allow air to enter the pump, THEN you fill the sump with water, that air cannot push open the check valve. So now the pump impeller is now in air not water. The pump Will Not Pump Air, Period! The vent hole gives the air a passage to escape & let water into the pump.

Relocate your vent hole & give to a try.
The noise at pump shut off is most likely due to the pressure in the discharge pipe Above the check valve. The check valve is slamming shut. High pressure above the check valve & suddenly No pressure below the check valve due to the pump "instant off" .
Not 100% sure, but, a pressure dampner above the check valve may help soften the water hammer.

 

[robertlynk]

Every sump pump manufacturer specifically describes in their installation instructions that you are to use a relief hole when setting up the sump pump and or ejector pump.

While per your theory you may feel that you are correct you must also realize the limits within which a sup pump operates.

This performance curve you speak of is limited by available amps.
The average sump pump operates within a range of 7 to 14 amps.

If you were to size a sump pump per this recommended performance curve you would quickly have a pump that could not function correctly within the limits.
Therefore, given the fact that it is required and in most cases must be provided to ensure that the pump does not lock, it is done.

I have literally drilled hundreds of holes in piping to prevent lock on installations by people professional and non who have argued the drilling of the hole, the where and the why. I have been to court to present a statement as evidence as required in a case where a plumber did not drill the hole and was sued for a fortune in damages.
I took the stand and upon being asked a question presented the manufacturers installation guide to the judge.
I never had to say a word. The hole was even illustrated.And exact location shown.
Go read your guide.

Exactly my point. These are small pumps limited by amp draw for a fractional horsepower 120V circuit. So, they have very low "shut off" head. Which means they can't overcome the static pressure of the discharge system - even at very low flows.

I design pumps for a living and understand the hydraulic properties of pumps. I'm not saying using a weep hole is wrong, just that it is a cheap way of getting a pump to work in a system it is really too small to perform in.

I think both points are valid the difference being that the sump pump has dried out.
causing the air lock thus the need for the relief hole.Where as a pump that never dries out must be sized to over come head pressure.