Septic Tank Effluent Pump (STEP) systems

[Pinwards]

For those who have designed, or worked with STEP systems, what is the highest pressure system that you have seen? I know they are normally called "low pressure" sewer systems, but the Orenco series of STEP pumps have models that go up to, and over, 400 ft of head (P30 & P50 series).

Anyone have experience with a high-pressure version of a STEP system? I'm just curious what kind of safety features you might include, or if you'd recommend breaking a site up into several lower-pressure sub-systems that flow to intermediate booster pump stations, rather than making a single high-pressure system.

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[bimr]

STEP systems do not normally operate at such high pressures. Note that the pumps have steep pressure curves so that the pumped volumes are low at the high pressures. The high pressures are useful to clear the piping when blockage occurs.

Of course, you could have a situation with an extremely long run or elevation change. Then you would encounter high head from the distance that you are pumping or high head from the elevation change, but it is unlikely scenario and probably not economical either.

The most economical system arrangement depends on the topography of the site. It would not be prudent to make any further comments without looking at the site.

Not sure what safety features that you are referring to, other than that the small diameter piping system should be rated for the pressures that will be encountered. Small diameter plastic piping can easily handle the pressures that you are discussing.

Why don't you contact Orenco for more info or talk to a pump supplier?

http://www.oasis-pumps.com/high-head-effluent.html

 

[Pinwards]

First, this is far from the only source that I'm seeking input from, and we're coordinating with Orenco and the supplier. This is just another source to seek advice from.

The site is quite mountainous, with an elevation range of over 300' difference between the highest and lowest lots, hence the high head scenarios. Essentially there's a high point in the middle that all flow must go up and over to reach the WWTP.

As far as safety, I'm not concerned about the pipe handling the pressure in daily operation, as it's rated to handle it. I was thinking more of a situation where the pipe gets hit during a future excavation, or other catastrophic failure. Check valves to ensure flow only goes in the intended direction, or something similar, could limit the amount of effluent discharged in that situation.

Just looking for some discussion on the topic. They're so often called "low-pressure" systems that I was searching for anyone who has worked on a higher pressure version.