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#204 - 07/15/13 05:45 PM Removing Calcium From HydroHot
Muniac Administrator Offline
enthusiast

Registered: 11/12/08
Posts: 247
Loc: Livingston, Texas
Calcium deposits can degrade the performance of just about every plumbing system. And if you're in areas with poor water treatment you'll likely see your plumbing get plugged up. Hot water lines exacerbate calcium build up.

The HydroHot's (HH) heat exchanger at 190F is a great place for calcium to collect. If you've noticed bubbling and reduced flow at the hot water faucet you might have a considerable build up of calcium in the HH's heat exchanger. To make sure you'll need to flow test the cold water feed into the HH. Also flow test the hot water line that feeds all the faucets. If these flow well you've narrowed things down to the HH and/or the anti-scald valve.

In anticipation of continued HH service I install 3/8" faucet feeder hoses to make future service activities easy. Read my article on Installing A New Anti-Scald Valve to see photos of how I used the faucet feeder hoses.

I flushed my heat exchanger out using a circulating pump (50 PSI) and 5% vinegar. To connect into the heat exchanger I simply made some garden hose to 3/8" compression adapters. I then capped off the PEX feeds and connected directly into the faucet feeder hoses.


Second round of calcium crap in the bottom of the bucket.

Keep the HH unit warm but not hot. Make sure it's turned off before you flush. In my case, the flush took about 2.5 hours to dissolve all the calcium and force it out. It's a good idea to delicately perform the flush. Keep the HH unit only warm. You can flush in both directions too to help break loose deposits. Keep in mind that chunks may clog the faucet feeder hoses too. They may need to be removed and manually cleaned. In my case the HH was in really bad shape and almost plugged solid. Individual situations will vary so proceed at your own risk. This method worked fine for me and completely restored proper hot water performance.

You can also connect your 1/2" female to garden hose adapter to the 1/2 NPT male connection on the HH hot water out. A larger diameter exit hose may help avoid clogs.

Complete slide show HERE.
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#205 - 07/18/13 11:36 AM Re: Removing Calcium From HydroHot [Re: Muniac]
Muniac Administrator Offline
enthusiast

Registered: 11/12/08
Posts: 247
Loc: Livingston, Texas
Follow Up Comments:

Several showers have been taken since the HH calcium flush out. Hot water flow and temperature are as they were 5-6 years ago when the HH was new. There is no deterioration in flow as the shower faucet control is moved toward hot. Also hot water temperature remains constant and doesn't fade as it once did. In short the cleaning has marked a BIG improvement in performance.

Our washer would often shut down on low water flow. Owing to low hot water flow the tub would take 40 minutes to fill. That time has now been reduced to about 20 minutes or less. This is for a setting that washes on hot and rinses on cold.

Calcium in the HH heat exchanger acts not only as a flow re-stricter but also an insulator. It impedes the heat transfer between the heat transfer fluid and cold water entering the HH. This also reduces the the cooling of the heat transfer fluid which causes the HH to cycle improperly. As calcium breaks loose, it can clog aerators in the faucets. Not a problem since aerators are easily cleaned but more of an indication that there is too much calcium build up.

Flushing the HH heat exchanger brings temporary relief as calcium will continue to build up. What was shown above covers an 8 year period. So the build up is a slow process. On a previous project I documented Installing A Pressure Gauge to keep tabs on my house water pressure. Having such information is very useful to include tracking the pressure drop through the HH heat exchanger. It will give you early indications of calcium build up. This would allow flushing the system before it gets really bad.

With all valves closed I set my house water pressure at 50 PSI. To check heat exchanger pressure drop simply open a hot water faucet and note the pressure. In my case I performed this test using the kitchen sink faucet. Pressure drop is 20 PSI through the entire hot water plumbing system that feeds the faucet. It's reasonable to assume calcium will build up first in the HH heat exchanger owing to its 190F temperature. Since the entire system has been flushed I'll use the 20 PSI as a hot water baseline. Of interest is the same pressure drop exists for the cold water system now as it should. This means comparing the pressure readings between hot and cold would also give indications of how well the heat exchanger is flowing. The two systems differ only in the hot water including a heat exchanger and anti-scald valve. In my case the anti-scald valve was flowing properly. On some buses, bypass piping of the HH through a control valve located in the plumbing bay may exist. Keep this in mind when trouble shooting your system.

Understanding Pressure Drop:

In a perfect plumbing system no resistance to flow would be encountered. That means opening a faucet would cause the house water pressure to be 0. In a practical plumbing system there is always resistance to flow, however. So the gauge reading upstream from the plumbing system will read the force (pressure) required to push the water through the PEX tubing, valves, elbows, etc. A higher gauge reading means more resistance to flow which implies restrictions. Since the number of elbows, unions, length of piping runs, diameter, valves, etc. remain constant an increase in pressure drop over time means calcium build up.
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Scott Bridgman, Why not join and post your own comments??
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