Sump Pump Physics Question FREE TOOLS

[Johnny Generic]

Here are the facts: Sump approx. 3' d x 2' w

Pump 1/2 hp with tether switch

Discharge pipe run approx. 8' straight up then 90 degree elbow into 4" drain pipe

No check valve on discharge pipe

So with that being said, when the water level gets so high in the sump the pump kicks in and pumps water out. When the pump turns off the water in the 8' rise returns back to the sump. ( no check valve ). Question is if a check valve is installed, would the pump have to work hard to pump water in rise out vs not have a check valve in? Wear and tear on pump more or less.

FREE TOOLS that was just a attention getter, sorry.

Johnny Genric

 

[Donald Cook]

Gotta have a check valve, For a shallow sump, your probably better of staying away from tether type pumps, they will have to pump a little more often, But get the check valve, you are probably pumping the same water over and over.

 

[Dagny]

It's fine.

 

[bwringer]

If it's only "re-pumping" the water from the rise, that's fine.

However, if the water in the outside pipe doesn't have a pretty good drop immediately, it can siphon much of that water back in.

Another consideration is freezing. I once lived in a rental with a leaky basement where the landlord added a check valve, and it was a lovely mess when the outside pipe froze.

 

[maxpat82]

it's fine, but a check valve cost to very much and you save "repumping this 8' column of water each time

 

[TractorJeff]

In my parents house they had the same dimensions and setup! Pumped the same 6 or 8 foot column all the time. The house was close to the creek so the pump ran about every hour. They usually lasted 8 to 10 years before the bearings would go out.

 

[Leaflessshadetree]

The check valve won't put much additional load on the pump. It actually will be easier on the pump.

 

[matt_i]

Worst case, double-pumping the water in the pipe on every cycle without the check.

2" ^2 * pi /4 * 96 = 301 cu in of water, 454 cu in/gallon.

So its 75% of a gallon of water that's being lost. You'd have to estimate the volume of the crock. If its a 10 gallon crock before it evacuates then that's 7% additional runtime. If it runs 1x per month then not so much worry. If it runs 1x per hour then more worry.

Personally there are a few assumptions that are faulty, the pipe is not likely a solid slug of water as its pumped up. I don't feel that the pump even knows that it is pumping harder to overcome the check seat or add inertia to the stationary water. If it doesn't trip the breaker its just using some more electrical current less than the FLA on the motor.

The thing that ***** is when the dynamics of the falling water goes back into the crock and jiggles the float around in such a way to trigger 5 more pump events. If the "automatic short cycling" starts then you are proverbially stabbing the pump in the back with a knife.

 

[pstnbly]

One reason for the check valve is to prevent the pump motor from spooling backwards as the water column returns to the sump. Spooling the motor backwards will shorten it's life.

 

[BIG BACCHUS]

I'm just here for the free tools....

 

[snyder]

If you are worried about the pump starting with the extra head caused by the check valve. Just drill a small hole in the discharge pipe near the pump. This will allow a free space between the check and the pump.

 

[redmondjp]

One reason for the check valve is to prevent the pump motor from spooling backwards as the water column returns to the sump. Spooling the motor backwards will shorten it's life.

????

Where did you hear this? After the motor turns off, it couldn't care less about what direction it turns. There are no brushes inside the motor.

To the OP: Add a check valve.

 

[D45]

I have 3 backflow valves on my setup........

Two smaller check valves under the pit cover (one for each pump) and one large valve about a foot above the cover

My sump discharge line travels about 20 feet until it reaches outside and then another 70 feet to the curb

 

[kbs2244]

I run without a check valve to give the pump motor a chance to spool up.

When I did some work for a plumbing contractor they always installed a check valve with a sump pump install because of code requirements.
But many of the plumbers removed them at their personal homes.

 

[jcthorne]

While the water in the discharge stand pipe would not drain back as soon as the pump stops, very few check valves are all that tight a seal and those that are (soft seated) do not last long before they leak. When the pump shuts down, the water will slowly leak back to the sump anyway. Just not fast enough to do any damage to the pump impeller. The check does protect the pump but will not keep the water in the vertical pipe.

 

[CJ7VFR]

...very few check valves are all that tight a seal and those that are (soft seated) do not last long before they leak. When the pump shuts down, the water will slowly leak back to the sump anyway. Just not fast enough to do any damage to the pump impeller. The check does protect the pump but will not keep the water in the vertical pipe.

This has been my personal experience with the check valves also. I have purchased the cheap plastic check valves with the rubber flappers from the big box stores, as well as some fairly expensive ones from plumbing supply places, and over time they all let the water in the vertical pipe back down into the sump hole.

But at least they prevent the syphoning others have mentioned, as well as preventing the water in the vertical pipe from just poring right back down into the sump hole.

Jim

 

[redmondjp]

Wow! So much incorrect information in this thread! What kind of check valves are you guys using? I install sump pumps here in rainy Seattle for my family and friends and also help to maintain sewer and septic pumps. A good check valve will not leak back!

And having a check valve there makes no difference in how quickly the motor starts up. If you don't believe this, put an amp clamp meter on the motor and try it both ways.