Grinder Pump Question (Use Limitations) 1

[zabrab]

I am reviewing a design for a duplex grinder pump station to serve 25 homes.

Looking back over my experience, it has really not included this type of application. My experience has been in projects that the same size and larger using non-clog pumps and grinder pump projects that are much smaller (grinders for one or two homes or a commercial establishment).

Way way back in my mind (I’m thinking the mid 1980s section), I seem to recall that when sizing a grinder pump station for a larger multiple home application, in addition to hydraulic considerations, there were manufacturer recommendations or even limitations on the number of homes that should connected to the station.

I haven’t seen anything in the current catalogs and In lunchtime chatter I’ve asked a couple of colleagues and they have never heard of this.

Has anyone heard of this type of limitation? If there is one, what is the basis for it? I presume it would be due to the shredding operation.

When we were kicking this around the table at lunch, the consensus solution was the pragmatic consideration of force main diameter. If you can use a 1-1/2” or 2” diameter force main, use grinder pumps, if your force main diameter is 3” or 4” for hydraulics, go to non-clog pumps.

What considerations do you use considering grinder pumps vs non-clog pumps?

 

[LHA]

In 2000, in PA, USA, I designed a duplex grinder pump station to serve 22 homes. We used a 4" force main, to provide for future capacity, but we didn't need a 4" to convey our loading. It was reviewed and approved by the municipal government, the municipal sewer authority and by PaDEP.

Do you prefer non-clogs to grinders? Why?

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

 

[RWF7437]

You may want to search for the website of Environment One. As I recall, they have much free information on grinder pumps and may even answer your questions directly if you send them an email.

 

[RWF7437]

http://www.eone.com/sewer_systems

 

[semo]

I see no need to use a grinder if the forcemain is 4-inches or larger.

Grinders require extra HP for the grinding and they wear out quicker because of the grinding.

As a 4-inch forcemain will pass a 3-inch solid like a non-clog, you will be better off with the non-clog.

25 homes on a grinder system seems high to me; but, the grinder companies might tell you different.

The flow from 25 homes might be pushing the upper flow limit on normal grinder pumps as well.

 

[francesca]

In Middle TN the local utility company approved the use of grinder pumps for 20-30 homes; I don't know the exact number. I suggest you contact your utility company to find out what they will accept. The size of the home will also be a factor as larger homes tend to produce larger flows.

 

[yogibear1]

In our system (Hillsborough County, FL) each household = 1 EDU and is assumed to contribute 200 g.p.d. 25 homes would contribute 5,000 g.p.d or about 3.5 g.p.m. Assume a peak factor of 3 so the max flow would be only 10.4 g.p.m which is not very much for a grinder station. We cut off grinders when they exceed 60 g.p.m and go to non-clogs.

You do want to keep a minimum force main velocity of 2 f.p.s. so a pipe size of 1.5 inches would be correct.

In our system the force mains in the ROW are a minimum of 4 inches before we can accept them from a developer; If they do no want to make it to our minimum then they maintain it.

Normally, we have to artificially increase the discharge head for the grinder pump discharge piping, by using an orifice plate - this keeps the pump operating point to the left side - towards the center of the curve, so that it does not cavitate.

 

[piffer]

Quick rule of thumb- Only use grinder pumps when flow rate is less than ~100 GPM. The grinder pump allows you to use a 1-1/2" or 2" discharge pipe because solids are reduced in size and can be transported at velocities> 2'/sec.
For higher flowrates, use 4" dia. pipe as long as you have transport velocity >2'/sec.
Grinder pumps are high maintenance (part pump, part garbage disposal), but they have their niche.

 

[Newbie176]

My town has recently put in sewers. I am told that I will need a grinder pump to facilitate moving the sewage from my home (3 person household) to the main. Since I am newbie to this, I soliciting information on the following:

1. Do I need to use a grinder pump or can I use a clog-free pump?
2. Which is better suited better this application?
3. What is yearly/monthly operating cost for these types of pumps (grinder/clog-free)?
4. What are the items (dirt, grease, etc.) that will cause these pumps to fail?
5. What are the average years of reliability for these pumps?
6. Lastly, how would you rank the following manufacturer of these pumps - (FE Myers, Barnes, Hydromatic, ABS, Flygt, and Stancor) or any others you feel should be included in the mix?

I know I've asked a lot of questions, but I am in area where I am not familiar. Your help will be much appreciated.

Thanks

 

[ccor]

Newbie176,

I suggest you look at the eone pump system. I think they are the best system for a single household.

http://www.eone.com

Small non-clog pumps are generally way to big for a single home. You have to oversize the wet-well to get adequate pump run time, and this can cause severe odor issues. The eone is a grinder/progressive cavity pump which can grind waste and free clogs in the FM because of the semi-positive displacement design. If your in the habit of dropping a lot of screws or nails down the drain, any grinder will have problems.