Sizing New Sump Pump for Existing Drainage Netwrok

[GrimesFrank]

When sizing a new sump pump for a network does one size it to pump against the head of all other pumps running simultaneously regardless of their duty?

The other pumps are for sumps with infrequent duty (e.g. floor drains for areas never used, emergency flood pit, etc.) If I size my pump (with regular duty) against those it will run to the right (i.e. high flow not balanced with in-flow) all the time. This seems fine but with the pump I have we're talking pump out times of 45 sec., hold times of 1 hour, then pump out again. This doesn't seem good for the life of the pump. I have heard rule of thumb is one would like sump pumps to run for 2 minutes (min.) Any truth?

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel

 

[GrimesFrank]

National,
You suggestion is pretty much spot on except.........

Have they got one to fit inside an 18 NPS Sch40 sump pipe?
That clearance requirement for a 2 NPS pump on the inlet has me in a corner.

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel

 

[Artisi]

Seems I missed the point way back where you said the sump is actually an 18" pipe, this probably changes the thinking a little.

However, you still need to study the pipeline characteristics for maximum and minimum operation and then look at all the pump sizings to see if they are compatable at the mximum condition as it is possible that you do not need pumps in series - but only a full study will tell you this and at the moment it is all guess work.

 

[GrimesFrank]

Facts;
Sump is a 18 NPS SS pipe (~24' length). Embedded into floor. Mtce pit floor drains empty into it. I realize the sump is a pittance.....can't be helped was like that when I got here.

Inflow = <10 GPM when used.
Duty = 2-3/mnth for about 16h duration (not constant)

Static Head = 60ft
Static Head +Head from other pumps in network = ~90ft min.

I know the variables involved I just wanted advice as to what in practice is 'acceptable risk' and what shouldn't be.
I believe sizing my pump to overcome the 'possible' head from the other pumps is an inefficient sizing.

I think I now have 4 options;
1) Size a big pump that normally will run way off BEP and only ever induce inrush current before it trips out on low level again.

2) Size an appropriate pump and live with the risk that there is a minute possibility that you will have to suspend operations until the other pumps aren't running

3) Size (2) pumps in series; a lead for regular duty and a lag to increase head when needed.

4) Size one of these AO sump pumps and just have the crew dial up the air pressure if more head is needed.

I like Option 4 as it eliminates the need for a PLC for level control that my Controls designer wants to implememt. As well as it is adjustable to run as you see fit and is not as complicated as a VFD.
My only problem I have with it is the literature says keep 1-1/2 pipe diameters clear in front of the inlet. Since my sump is 16.876 in. across and the footprint of a 2 NPS pitbull is 16.6 in. I'm kind of pooched.

Comments?

Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel

 

[nationalpump]

I would be interested to know whether or not you could have a Pitbull assembled in such a way that it would fit your application. The intake clearence dimension is probably recommended so that the intake does not get plugged by any solids you may have in your sump system.

If you have any space on top of the sump pit you could pump to a small open stainless steel tank and pump out of the tank with an air operated diaphragm pump (or a Pitbull). This leaves you with the purchase of two "correctly sized" pumps and a small side tank.

I will be interested to know what you come up with. Good Luck.