Sump pump discharge 1.25 vs 1.5 inch

[ironmanvsaquaman]

Hoping some folks can educate me on the advantages/drawbacks between 1.25" and 1.5" discharge hose for a sump pump.

I have a 3/4 horse, 80 gal/min sump pump. Water gets pumped straight up about 17 feet before going into a long horizontal run (with slight downward slope) of about 80 feet of 1.5-inch PVC pipe. I'm not using a check valve due to risk of freezing. I'm using hose for the vertical section, and am trying to figure out if it's better to use 1.25 or 1.5 inch hose.

My initial thought is that 1.25 would be a little better since that's a little less volume that will drain back into the pit after the pump shuts off.

Should I have any concerns about things like pressure/velocity/strain on pump with the smaller diameter hose?
Anything else I'm overlooking?

 

[Bannerman]

80 GPM will be achieved at 0 feet of lift. The head capacity of the pump will determine the flow rate after 17' of vertical rise. For instance, if the pump is capable of only 20' of head, then it's likely, the pump will discharge at best, only a couple of GPM after pushing water 17' vertically, whereas a similar 80 GPM pump with higher head capacity, maybe capable of discharging 30-50 GPM after 17' of vertical rise.

pumped straight up about 17 feet before going into a long horizontal run (with slight downward slope) of about 80 feet of 1.5-inch PVC pipe. I'm not using a check valve due to risk of freezing.

Reconsider the need for a check valve.

Regardless of pipe diameter, as the pump is located a substantial distance lower than the 80' section of horizontal pipe, the 17' of water draining back into the sump pit, will cause most of the water within the 80' horizontal section to be also siphoned back into the pit.

Assuming the 17' vertical section is within heated space, and the 80' horizontal section is external and exposed to freezing temperatures, then it's really only the horizontal section that is at risk of freezing.

Placing a check valve directly above the pump will prevent the 17' vertical column above the CV from draining back, but the 80' horizontal section will then drain slowly as air will need to enter the open discharge end to eventually break the vacuum within the 80' section.
,
To cause the 80' horizontal section to drain out rapidly, install a vacuum breaker device directly above the 17' vertical section. A vacuum breaker will not permit air to enter or water to leak out while the pump is supplying pressure, but once the pump turns off, the vacuum created downstream, will cause the vacuum breaker to permit air to enter the downstream section, thereby breaking the vacuum to permit the 80' section to drain out as rapidly as possible.

If the 17' vertical section is also not within heated space, by not using a check valve but continuing to use a vacuum breaker at the highest point, will cause air to enter when the pump turns off, allowing the 17' vertical section to drain back slowly into the pit below. Because the vacuum will be broken by the air entering through the vacuum breaker, the water within the 80' section will not siphon backward, but will drain out rapidly as intended.

The image below, while not an exact representation for your application, does show how your system could be similarly configured.

 

[Sponsor]

 

[Fitter30]

Sump pumps in their directions most is not all call for a hole in the pipe in the sump pit below the pump check valve. Drain back for riser. Calculator for gallons. They want the check above the pump so it can siphon water back through the pump at shut off.
1.25. 1.08 gallons for 17'
1.50. 1.56 gallons
www.rhomarwater.com/Calculator.html

 

[ironmanvsaquaman]

If the 17' vertical section is also not within heated space, by not using a check valve but continuing to use a vacuum breaker at the highest point, will cause air to enter when the pump turns off, allowing the 17' vertical section to drain back slowly into the pit below. Because the vacuum will be broken by the air entering through the vacuum breaker, the water within the 80' section will not siphon backward, but will drain out rapidly as intended.

This is exactly similar to how I have it set up. No check valve at the pump, but a vacuum breaker an AAV at the high point where it switches from hose to pipe. When the pump shuts off, the 80-foot horizontal pipe section should drain outside, and the vertical hose section should be draining back into the pit through the pump.

This setup has been in place for some time and working fairly well, but the hose I've been using is that cheap corrugated black polyethylene drain hose. The stuff doesn't last and I'm tired of fixing leaks. I'm planning on replacing it with spa hose.

The existing poly hose is 1.25 inch. Since it's getting replaced, I'm trying to decide whether I should stick with 1.25" for the spa hose, or step it up to 1.5".

That brings it back to my original question: What are the tradeoffs between 1.25 and 1.5 inch discharge hose?
Aside from slightly less volume of water draining back into the sump with the smaller diameter hose, I can't really think of any other factors to consider. I just wanted to see if any members here can point out some factors I'm overlooking. Pump life, maybe?

 

[ironmanvsaquaman]

Sump pumps in their directions most is not all call for a hole in the pipe in the sump pit above the pump check valve. Drain back for riser. Calculator for gallons. They want the check above the pump so it can siphon water back through the pump at shut off..
1.25. 1.08 gallons for 17'
1.50. 1.56 gallons
www.rhomarwater.com/Calculator.html

Well golly! The volume of water in either size hose is a lot less than what I would've guessed.

I've still got the literature that came with the pump. Doesn't say anything about a hole in the discharge pipe. It's equipped with an anti-airlock hole. Same thing?

 

[ironmanvsaquaman]

80 GPM will be achieved at 0 feet of lift. The head capacity of the pump will determine the flow rate after 17' of vertical rise. For instance, if the pump is capable of only 20' of head, then it's likely, the pump will discharge at best, only a couple of GPM after pushing water 17' vertically, whereas a similar 80 GPM pump with higher head capacity, maybe capable of discharging 30-50 GPM after 17' of vertical rise.

Specs for my pump are:
80 gal/min @ 0 feet
38 @ 30

Should be doing 58/59 gal/min @ 17 feet.

 

[Reach4]

You really should add a check valve near the pump, unless you will not be able to prevent the pipe between the pump and the high point from freezing. Also put a 3/16 hole above the pump and under the pit cover and below the check valve. Angle the hole so it sprays downward.

Pipeline Pressure Loss Calculators - http://irrigation.wsu.edu/ is a simple calculator to determine pressure loss (dynamic head) based on flow rate and diameter and length. Dynamic head gets added to static head from altitude rise.

 

[Master Plumber Mark]

You will probably burn out the pump or the switch over time without a check valve in the line.....

if the line is in a heated area in the crawl space then all you have to worry about is where it exits the building
that needs to be insulated or you pipe it above the exit pipe so it has to fall down into the line going out of the house...
and its wiser to have a larger line outside the house instead of just a 1 1/2 pipe...

I tell people to install a
4 inch corregated black roll of drainage pipe outside so it can never totally freeze up

also, lots of fall is important in bitter cold temps,, pipes sag over time and its just wiser
to have something too large that has good fall on it that is almost impossible to freeze up totally

 

[Bannerman]

This is exactly how I have it set up. No check valve at the pump, but a vacuum breaker at the high point

There was no mention of a vacuum breaker in your original post.

If the vacuum breaker is preventing air from entering the top of the vertical column as shown in the diagram above, then I expect the 17' column of water is not draining into the pit as air would need to enter to break the vacuum within the column. Without draining, the 17' section of vertical hose, would always need to support the weight of the water within it, which is likely contributing to the failure of that hose.

One concern with the vertical column draining rapidly through the pump, is the potential for the pump to spin in reverse by the force of the back flow. In placing a small drain hole ABOVE a check valve located just above the pump, any drain back will not then pass through the pump, but air will need to enter at the top of the column to allow the water to drain.

Unless your vacuum breaker permits air to enter both the horizontal section and vertical column, then you will need to provide an appropriate means for air to enter the top of the vertical column.

While you could simply drill a small hole through the fitting directly below the vacuum breaker, water will then squirt out whenever the pump is operating. An alternate method to introduce air without leakage will be to utilize 2 compression fittings and a short length of 1/4" tubing, bridging between the inlet and outlet of the vacuum breaker. In this manner, air entering the VB into the horizontal outlet, can flow back into the top of the vertical column, thereby breaking the vacuum and allowing the column to drain at the rate governed by the diameter of the drain hole located just above the check valve.

Restricting the flow rate exiting a centrifugal pump will typically reduce the workload on the pump since less water will be pumped per minute. Lower workload also usually reduces the amps needed to run the pump, which then reduces the amount of heat developed while running.

As most pump's are equipped with motors rated for continuous duty (check yours), reducing the exiting flow rate, will then cause the pump to run longer each cycle, which is a positive thing. With continuous duty motors, it is frequent cycling that negatively impacts their lifespan, so longer run times as a result of a lower flow rate, should reduce the cycling frequency and further reduce heat buildup. Unfortunately, always needing to re-pump the drain back from the 17' vertical column, will reduce efficiency and will also add to the frequency that the pump will need to run.

 

[ironmanvsaquaman]

There was no mention of a vacuum breaker in your original post.

I misspoke. The system has an AAV, not a vacuum breaker.

 

[Bannerman]

system has an AAV, not a vacuum breaker.

We can only provide advice based on the information each poster provides.

An AAV will not prevent air from entering the vertical column, so a vacuum lock will not prevent the vertical column from draining.

The rapid backflow through the pump remains a concern, so using a check valve and small drain hole above, will prevent backflow through the pump impeller, and will also cause drain back to occur less rapidly and in a more controlled manner.