The Water Blog Frequently Asked Questions about Wyckomar UV Systems #9

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Flow Rate Ranges – How Can One UV Model Have Different Flow Rates?

Posted on May 13, 2019

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Flow rates are an important component when deciding on the proper size of any UV system.

The purpose of a flow rate specification is of course to help users and contractors select the proper sized UV for their particular application. At Wyckomar we are presenting our UV systems with a variety of flow rates and this FAQ will answer the question of "how can one model have different flow rates?"

Let's first go back to the basics.
UV Dose applied is a function of (among other things) the water quality at the site, and the flow rate. We design our UV systems to be as useful as possible across a wide variety of applications and have traditionally used a basic flow rate (by UV model) to determine the flow rate specification. As you know, the UV dose applied will vary with flow rate (the lower the flow rate the higher the UV dose applied for a given water quality). Our decision to show a range of possible flow rates for each UV model we manufacture is based upon the fact that there are several "generally accepted" UV dose standard rates in the market today so we want to highlight the flexibility of using UV as a primary form of disinfection under different "generally accepted" UV dose standards.

Currently there are typically three standards of UV dose applied in the market today.

The first is an older standard typically referred to as the "public health standard". This comes from many older public health studies that have been published over the years and many of which may still be in use today. This standard requires a UV dose of 16 mJ/cm² to be applied at a specific flow rate.

The second standard is referred to as an "industry standard" and is used by many UV manufacturers and others in the UV industry. This standard typically calls for a UV dose of 30 mJ/cm² to be applied at a specific flow rate.

Finally there is a standard known as "ANSI" (which means American National Standards Institute) which is fast becoming the "normal" UV dose favored by the industry and it's users. This standard requires a UV dose applied of 40 mJ/cm² at a specific flow rate.

In order to show a broad spectrum of UV applications, and the flexibility of UV as a primary disinfectant, we are showing our UV Dose data using all three of these standards. An example is appropriate at this point:
Let's select the Wyckomar model UV-700 which has traditionally been thought of as a typical 8 GPM (30LPM) UV system. Assuming the local water supply is at 95% UVT (a measurement of water clarity and quality) then the UV-700 will allow the following flow rates and provide the coincident UV Dose at that flow rate:

UV Dose at Different Flow Rates

Flow Rate	UV Dose Applied
24.3 GPM (92 LPM)	16 mJ/cm2
17.2 GPM (50 LPM)	30 mJ/cm2
9.8 GPM (37 LPM)	40 mJ/cm2

It's easy now to understand how one model of UV system can have several different suggested flow rates. It really depends on how much UV Dose is required for the application. Remember to review our UV Inactivation Chart in order to determine the optimal UV Dose for the job.

We have attached a Data Table showing the UV Dose applied for each of our standard UV systems at each of the three standards noted earlier in this article. The table makes it very simple to choose your UV model for the intended applications.

It is also possible (we have done it many times) to build a UV system to provide an extreme UV Dose (for example +200 mJ/cm²) for applications that require it. These extreme dose UV appliations are becoming more common in agriculture and also in food manufacturing and are desired by customers due to several factors including increased regulation and particularly "hard-to-kill" pathogens.

Please contact the sale desk sales@wyckomaruv.com for more information

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