Sizing New Sump Pump for Existing Drainage Netwrok
Sizing New Sump Pump for Existing Drainage Netwrok
(OP)
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?
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





RE: Sizing New Sump Pump for Existing Drainage Netwrok
RE: Sizing New Sump Pump for Existing Drainage Netwrok
45 seconds would be at the short end of the range.
You did not say how large your sump was.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
It may be beneficial for you to carefully determine and set the running schedules of all pumps using a timer or other control system such that you always have only one pump running, or to schedule a group such that they always output the minimum possible head at any given time. As such you may be able to minimize the overall discharge head and system flow capacity at any given time.
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"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
Thats the key BigInch. My 'competitors' are an infrequent must;
1) FD(s) from unused areas
2) Dyke area in case something spills during drum changing
(Drum changing < 1 per month)
3) Pit drainage after emergency sump pump testing complete
(testing < 1 per 6 months)
My arguement has been;
"If another pump happens to be running then we hold (or they hold) pumping until its done."
My senior's arguement has been;
"You must be able to pump against the worst case, its just standard practice."
I'm trying to show him that my 2 NPS (80ft @ 20 GPM) pump is normally operating in a range not recommended. If my pump was infrequent as well I wouldn't mind, but it just so happens that my sump is a wash station (18"Dia / 30ft sump) so I'm thinking I'll be burning these pumps out.
Am I out in left field?
Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel
RE: Sizing New Sump Pump for Existing Drainage Netwrok
In the design of low pressure sewer systems this application is commonly encountered. Dwellings all have a sump pumps reporting to a common sewer system network. The most challenged pumps have to wait until the system head is reduced so that they can operate. The sumps have to have sufficient free board so that they do not overflow whilst waiting the opportunity to run.
The pumps start and if the pressure is greater than set point they stop and try again after a fixed time period. If all your sumps levels are known by the SCADA then it is even easier.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
If you are following the plumbing code, then the discharges cannot connect to each other, just for this reason to avoid different pressures preventing a pump to operate.
Connections to the drainage pipe should occur on the top so that each pump is pumping against/to atmospheric pressure and avoid this problem.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
I guess you have now realised that sump design is not a hit and miss exercise but requires a careful study for operation under all conditions.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
Yes Artisi, I realized unless you are a specialist, most designers treat sumps with the "Eh...whatever" attitude which made my job a whole lot difficult.
I think I've hit upon a compromise though.
Do you have any opinions about a lead/lag sump pump set-up?
I proposed to put to 2 smaller head pumps (~50 ft shutoff) put them in series and when the second one is needed (i.e. sump keeps rising due to insufficient head) it'll kick on.
I get what I want (operating at BEP and balanced in/out flow) and my supervisor gets what he wants (never have to stop operations due to inability to drain)
I have the cubicle to power another pump and my controls guy is using a depth sensor rather than float switches so its just and extra couple lines of code in the PLC.
Critiques please.
Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel
RE: Sizing New Sump Pump for Existing Drainage Netwrok
Credit to you for the idea.....
Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel
RE: Sizing New Sump Pump for Existing Drainage Netwrok
<anonymous>
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
I hope you mean in parallel - not series.
The first thing you should do is to produce a system head curve for the pipeline based on anticiated flow rates from all the pumps when operating, from there you can superimpose the individual pump performance curves over the system curve to check performance of each pump under maximun conditions - if you know the max. inflow and max. flow rate for each of the pumps you can then estimate the sump size.
For interest - do the other sumps have sufficient capacity if you are adding further flow to the pipeline?
RE: Sizing New Sump Pump for Existing Drainage Netwrok
I'd consider putting a monster there .... <ready for this?> with a VFD! He'd be able to match the required head and pump more flowrate whenever he turned up the dial. Sounds like that's just what is needed here... for a change.
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
RE: Sizing New Sump Pump for Existing Drainage Netwrok
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
I was proposing two smaller pumps in series to give me a constant flowrate (to pump out my inflow) but have a choice of heads depending on how many other pumps are running in the network.
BigInch I was hoping I didn't need a VFD as I've never dealt with them before as well as I only had two scenarios I was concerned about (1 pump running OR all pumps running). I guess this becomes a 'learning opportunity' now. ;)
I was hoping to install a 2 NPS discharge submersible sump pump (~1-1.5hp). Is a VFD still suitable?
Today is gone. Today was fun.
Tomorrow is another one.
Every day, from here to there,
funny things are everywhere. ~'Dr.' Theodor Geisel
RE: Sizing New Sump Pump for Existing Drainage Netwrok
I didn't know the maximum power requirement would be so small. Now I have to change my thoughts too. In this very low power consumption case I would rather use 1 constant speed pump x 3 HP and always have too much head rather than fooling with a vfd, as running 3 HP when you only need 1.5 just won't ever save enough power to make a vfd worth the effort of installing it.
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
The problem you are facing may be able to be solved by an air operated submersible. The "Chicago Industrial Pump Company" produces the PITBULL pump line which should work in your situation. You would need to size the pump to operate slightly above the maximum header pressure which would allow the sump pit to always be drained. The output of the PITBULL would drop as the pressure in the line increased just like a centrifugal pump though you would not have to worry about "running off the BEP" and damaging the pump. There are other things to consider (air consumption, size and shape of available pumps, cost etc.) when looking into a PITBULL so this may not be right for your application. I would be interested to hear what you think. Thanks and good luck.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
http://virtualpipeline.spaces.msn.com
"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
RE: Sizing New Sump Pump for Existing Drainage Netwrok
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
RE: Sizing New Sump Pump for Existing Drainage Netwrok
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.
RE: Sizing New Sump Pump for Existing Drainage Netwrok
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
RE: Sizing New Sump Pump for Existing Drainage Netwrok
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.