The Pump Supplier's Bundle

A certain pump supplier routinely seeks to overturn engineering specifications by offering to replace Omicron with their alternate filtration product as part of a “bundle with our pump package” offer. It seems the ease of procuring from a single supplier allows them to avoid scrutiny of the technical limitations of their product line.

If the respective technologies are not examined at the time of specification, only after the pump supplier’s filter has been bought, installed and put into service are its performance limitations revealed. At that point, a service call can’t resolve them, the cost of remediation is prohibitive, and even the required footprint for the correct solution might no longer be available.

Let’s look at an instance of a multi-residential building where the pump supplier’s “10 micron” filter is installed. Once in operation, it began to send a massive amount of water down the drain, day after day. Within a few weeks after start-up, the building engineer had no alternative but to put it into bypass mode and keep it off-line. The owner’s investment and commitment notwithstanding, the building does not provide filtered water.

Here’s why bypass was the expected outcome of “buying the bundle”.

Automatic screen filtration uses a pressure differential sensor to detect whether a backwash cycle has successfully restored the screen to clean status. If yes, the filter returns to normal filter mode. If no, it attempts another backwash cycle. Typically, backwash cycles occur between 6 and 12 times daily, depending on water conditions, and the amount of water used for cleaning is modest, about 1 - 2% of the total daily water use at the building filtered.

If the cleaning mechanism cannot successfully backwash the screen, then the system will cycle over and over in an unsuccessful attempt to clean the screen. Either that or the system will go into bypass mode, automatically or manually.

The requirements for 10 micron filtration

Once 10 micron became the new standard for NYC projects, the pump supplier began claiming that they too offered 10µ. Here’s an actual quote, word for word, from an email they sent to an engineer:

"We could offer the filter in 10 microns as well. A 25 micron filter will backwash less than a 10 microns filter. But we can supply it in 10 microns if that is your preference. No, the footprint will not increase. It will be the same set-up and same filtration system if we change [from 25] to 10 microns."

The writer fails to acknowledge the immutable relationship between filtration degree and required screen area.

This rule is constant for any filter, size or application, whether you are sizing for 1 gpm or 10,000 gpm. If you change from 25µ to 10µ, at the same flow rate, you must increase the screen area by a factor of about 250%. Which translates to a somewhat larger footprint.

Moreover, as pore size decreases, the force required to capture collected particulate matter during cleaning cycles increases.

This force cannot be realized unless the suction scanner nozzles come into direct contact with the screen, as seen below from an Omicron 21300-10.

Without this contact, the turbulence in a water environment will negate the suction power. With even a fraction of an inch distance, the screen cannot be successfully cleaned.

If you examine the suction scanner of the filter provided by the pump supplier, you’ll see a small distance between the edge of the scanner nozzle and the screen.

To expect a fine filtration screen to be quickly cleaned without scanner contact requires magical thinking. Which seems to be the basis for this operation video produced by the manufacturer:

Conclusion

As we have noted, the two crucial requirements for fine screen filtration are sufficient screen surface area and ensuring high velocity suctioning of dirt off the screen during cleaning cycles. Unless both are in play, even coarser screen filtration is not a viable solution to the challenges of NYC water conditions.

No one gets to rewrite the laws of mechanical physics. When we offer 10µ screen filtration, our sizing is designed to accommodate the maximum flow rate. If you cannot accommodate or don’t need 10µ, you can use a smaller system which won't require as much screen area. Whatever micron rating you select, every system we supply will include suction scanner nozzles that actually contact the filtration screen.

Here is one of our most common 10 micron solutions, the Omicron 21300-10. This is what it takes to deliver reliable 10µ for a flow rate of up to 400 gpm in NYC water conditions.

For a complete set of engineering and specification files for this model or any other Omicron solution, please contact us