Water system monitoring

Water treatment system component	Sampling site	Test	Acceptable level	Recommended frequency of measurement
Feed water	Sampling port in the feed line to the water treatment system	Chemical analysis	Variable depending upon the contaminant*	Every 3 months^¶ or when the water provider changes the composition of the feed water or when the source of that water changes.
Multimedia filters and/or beds	Pressure gauge before and after the filters and/or beds	Component inflow versus outflow pressure difference and comparison with baseline pressure difference	>10 mmHg above baseline	At the end of every day.
Softener	Sampling port at the outflow of the softener	Hardness	<1 GPG (17 PPM)	At the end of every day.
Carbon beds and filters	Sampling port located between the first and second carbon bed^Δ	Total chlorine^◊	≤0.1 PPM	At the start of the day and every 4 hours.
		Monochloramine^◊	≤0.1 PPM	At the start of the day and every 4 hours. Measurement of monochloramine is not necessary if total chlorine is measured with an acceptable level of ≤0.1 PPM.^◊
	N/A	Empty bed contact time (EBCT)	>10 min	Following any change in the maximum water flow rate or any change in carbon volume.^§
Reverse osmosis	N/A	Percent rejection	Based on water analysis, usually >90%	Continuously (measured by reverse osmosis system).
Reverse osmosis	N/A	Percent recovery	Depends on facility, based on trends	Continuously (measured by reverse osmosis system).
Deionizer	N/A	DI resistivity	>1 megaohm•cm	Continuously (measured by the deionizer resistivity meter).
Ultraviolet irradiator	N/A	Ultraviolet energy output	>30 mW•s/cm² (>16 mW•s/cm² if UV calibrated meter)	Daily, or in accordance with the manufacturer's recommendations if otherwise indicated.
Dialysis water	Sampling port prior to the distribution loop	Chemical analysis	Variable, depending upon the contaminant^¥	Every 3 months or when: The quality of the feed water demonstrates changes in the measured chemical contaminants. The reverse osmosis membranes are changed. The reverse osmosis percent rejection drops below 90%.
	Sampling port in the return line of the distribution loop^‡ Sampling port in the distribution loop outlet to each treatment station	Colony count or total viable microbial count	<100 CFU/mL with an action level of 50 CFU/mL^†	From the return line of the distribution loop: monthly^‡ From the outlet of each treatment station: annually**
	Sampling port in the return line of the distribution loop^‡ Sampling port in the distribution loop outlet to each treatment station	Endotoxin	<0.25 EU/mL with an action level of 0.125 EU/mL^†	From the return line of the distribution loop: monthly^‡ From the outlet of each treatment station: annually**

GPG: grains per gallon; PPM: parts per million; N/A: not applicable; EBCT: empty bed contact time; DI: deionized; CFU: colony-forming units; EU: endotoxin units; CMS: Centers for Medicare and Medicaid Services.
* For details, please refer to the UpToDate topic on contaminants in water used for hemodialysis.
¶ The bare minimum frequency of testing feed water is annually.
Δ A sample should also be collected from the port located after the second carbon bed if the concentration of total chlorine or monochloramine exceeds the acceptable level in the sample obtained from the port between the two carbon beds. Systems with parallel sets of two carbon beds in series have a sampling port between the first and second bed of each parallel set. Total chlorine or monochloramine levels should be measured in samples drawn from the sampling port of each parallel set of carbon beds.
◊ Total chlorine is the sum of "free" or "non-bound chlorine" and "combined chlorine (monochloramine)." There is no direct way to measure monochloramine. It is measured indirectly by calculating the difference between the levels of total chlorine and free chlorine.
§ Note that some regulatory agencies, such as CMS, might require periodic recalculation of EBCT regardless of whether or not there has been a change in operating conditions.
¥ For the list of possible contaminants and acceptable levels, please refer to the UpToDate topic on contaminants in water used for hemodialysis.
‡ More comprehensive sampling, for example from the first station in the loop, last station in the loop, reverse osmosis product water, and storage tanks, can be required in some circumstances, such as for facilities subject to CMS regulations.
† An action level should be set based on knowledge of the microbial dynamics of the system. Typically, the action level will be 50% of the maximum allowable level.
** Testing may be conducted on a rotating basis, with some stations tested each month, as long as all stations are tested at least annually.

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Water system monitoring