Frequently Asked Questions and Troubleshooting Tips >>

Check the following for answers to frequently asked questions and troubleshooting tips about the deionized water waters systems.

As a user of a service DI water system, what data should I collect?

Whether you are considering a new vendor, a new installation or trouble shooting your current system, it’s important to have the following information on hand:

• Keep a log of the incoming TDS

Why? – Weather can affect the quality of the water being treated. If the TDS (total dissolved solids) in the water goes down fewer tanks may be used. If the TDS goes up, more tanks may be used. If the TDS hasn’t changed and more tanks are being used, talk to your vendor, as there may be a problem.

Some Reasons for More Tanks:
• Snow and ice - the local department of transportation or municipality is putting brine or salt on one the roads. As snow and ice melt, the salt runoff enters the water sources and causes the TDS to increase.
• Drought – During periods of little rain the water sources are evaporating, and reservoirs are low, which causes the ratio of total dissolved solids to increase.

Some Reasons for Fewer Tanks:
• Rain – During periods of increased rain, the reservoirs, rivers, streams and lakes are high, which causes and the ration of solids to decrease.



• Keep a log of how many gallons are going through the system. This can’t be done without a meter.

Why? – A DI water system is designed based on the TDS, flow rate and number of gallons you need to treat. Assuming you’ve ruled out a TDS increase/decrease as noted above, one of two problems may occur:


• The DI tanks are exhausting prematurely because they are undersized or you are using more water than in the past.
• The DI tanks may appear to be exhausted or the conductivity is inconsistent because the system is oversized. As a result, the water going through the ion exchange resin is channeling, (too low water flow for the size tank). The system is oversized because you are using less water than in the past.

How can I optimize my DI system?

• Have you considered using a two-tank separate bed system?

Why? – Incorporating properly sized separate bed, cation and anion ion exchange tanks before the mixed bed ion exchange tanks will prolong the life of the mixed bed tanks down stream of these units. This makes the most sense for high flow rate applications where 30" or 36" DI water tanks are being used.

In many cases, the cost to regenerate the separate beds is less than the mixed bed. While you may use more separate bed cation and anion tanks, the net cost at the end of the year is less because you’ve decreased usage of the more expensive mixed bed tanks.


• Have you considered using weak base anion exchange tanks instead or in addition to the strong base anion?

Why? – What is your water quality requirement? If Silica and CO₂ removal are not a concern, weak base anion exchange resin will work well and the cost to regenerate is generally less.

If your primary concern is Silica and CO₂, then you might want to use a weak base anion tank ahead of the strong base anion exchange tank. The weak base anion acts as the roughing tank leaving the strong base tank with more capacity to remove the silica and CO₂.


• Are your two tank separate bed cation anion tanks configured correctly?

Why? – Depending on your particular water chemistry, you may get longer runs and fewer tank exchanges if you have an anion tank that is larger than the cation tank or vice versa. Equally sized cation and anion tanks will not exhaust simultaneously in many cases. Consequently, one of the tanks may be taken off line prior to exhaustion and not used to its fullest capacity. Supply your vendor with a full cation/anion balance to determine the best configuration for your application.

What is the difference between parallel and series configurations?

• Series Configuration – In this configuration the water runs through the first tank, then through the second, third, etc. Some common DI tank configurations are as follows:


• Carbon -> Cation -> Anion
• Carbon -> Cation -> Anion -> Mixed Bed
• Carbon -> Cation -> Anion -> Mixed Bed -> Mixed Bed
• Carbon -> Mixed Bed -> Mixed Bed



• Parallel Configuration – To accommodate higher flow rates or to increase the time between tank exchanges, two or more trains or banks of tanks can be installed and operated side by side. A system that runs parallel will result in lower flow rates per train or banks but will have the same overall flow rate as required for the application.

Where are the conductivity lights or meters supposed to be placed?

• Carbon -> Cation -> Anion
• Carbon -> Cation -> Anion -> Mixed Bed
• Carbon -> Cation -> Anion -> Mixed Bed -> Mixed Bed
• Carbon -> Mixed Bed -> Mixed Bed

Contact General Water for Industrial and Commercial DI Water Service
General Water Services Corp. is a leading water treatment systems company and a WBENC-certified woman-owned business. Contact us for further assistance.