36 years of experience
Over the last 36 years, I have collected a few nuggets of plumbing design knowledge and maintenance wisdom from experience troubleshooting plumbing systems. I did not find the solutions written on any pages of design books.
The nuggets of wisdom in this article might help keep you out of hot water. I am often asked to investigate buildings where there have been plumbing system failures. The failures mostly have to do with design errors and installation errors. Occasionally, there is a product defect, but, more often than not, it has to do with someone not thinking about what they are doing.
I am sharing these experiences with you so that you can learn from them and avoid the problems associated with some of these stories. The names and places have been altered or removed to protect those involved. If you think this story is about you, it probably is not. These are a few of the stories I hear over and over.
Investigation No.1 – Contractor in hot water
Once upon a time, there was a towering high-rise condo building with million dollar condos planned for a location not too far from our nation’s capital building. It was built by a developer with great expectations and a tight budget. The developer commissioned a set of preliminary drawings to be prepared by an architect/engineer and the developer used the drawings for preliminary pricing. A general contractor convinced the owner they didn’t need to complete the drawings, and said he could complete the project as a design-build project. I wish I had a dollar for every time I heard a story like this one.
The owner agreed to let the general contractor build him a building with nothing more than a schematic set of drawings and a written scope document. They proceeded to finish the building without engineered drawings. I heard the contractor had an engineer on staff. The preliminary drawings called for separate hydronic and domestic hot water systems. This is where the contractor decided to save some money.
The hydronic system was black steel and the plumbing system was copper. The contractor decided to combine the two systems and make a compromise on the hot water piping and storage tank material with galvanized pipe and galvanized tanks for the combined heating hot water and hydronic system. Bad decision. The heating hot water system was supposed to be 200°F, the domestic hot water system was supposed to be 140°F. The compromise temperature was 170°F (for a while) galvanized piping, used with an open (oxygenated) hot water system caused corrosion to occur at a very high rate, very quickly. This caused iron oxide to appear, and the hot water coming from the faucets looked like orange juice.
A quick call was made to a water treatment company, and the guy who was used to dealing with heating hot water systems sold them a system to inject large amounts of a chemical into the piping to raise the PH and cause the piping to develop a layer of scale and coat the rusty surface. Not only did it coat the pipe walls, but it coated the strainers, control valves, heating surfaces, pump seals and valve seats and shower valve controls, shower heads faucet outlets, etc. (They all had tan colored stalactites.) The coating caused isolation valves to seize up. It stained fixtures and caused heat exchangers to build up scale to the point the flue gas temperatures when very high and there was a colossal waste of energy. The strainers and balancing valves on the hot water return system plugged up, and hot water stopped flowing in recirculation lines. Check valves and backflow preventers seized up in the open position and were unable to prevent reversal of flow.
Thermostatic mixing valves were designed to reduce the 170°F hot water to120°F to protect building occupants from the high temperatures of the heating hot water in the combined system started to seize up and not operate properly. The heating hot water at 170°F was not hot enough for the heating coils which were designed for 200°F heating hot water and the tenants were cold in the winter. When all of these system problems started to appear, the building maintenance crews did not know what the cause of all the problems were. So, they blamed a valve manufacturer for the inability of the valves to balance the flows and control the temperatures. The valve manufacturer knew this system was unusual, so they called me and asked me to have a look. I found many code violations, and they did not follow good engineering practices. I found that the system never had an engineered set of drawings. The preliminary drawings were submitted for plan review. The contractor did not follow the plans and combined both systems into one system, without adjusting the pipe sizes and he used the wrong material. The high-rise building needed at least three pressure zones, and the contractor put all of the water heaters and pumps in the basement.
There were three similar buildings, each with a triplex booster pump package on the hot and cold water systems. The relief valves on the water heaters began spewing water when the system was pressurized because the water heaters were in the basement and the system pressure was well above 150 psi. So, the relief valves were removed and replaced with relief valves with a much higher relief pressure. (This voided the warranty of the water heaters.)
The hot water system had booster pumps that served pressure reducing valves. The pressure reducing valves on a hot water system lasted just over six months, and had been replaced several times by the time I investigated the system. Then, the seats were worn out and the full system pressure of 260 psi plus or minus was on the entire system. Looking at the thermal expansion tank, many other components in the basement mechanical room, the components had a maximum working pressure 150 psi printed on the labels and pressure gauges showed pressures in excess of 260 psi. The pressure gauges were reading close to 260 psi. (More voided warranties.) About 75 percent of the pressure gauges was the needles broken off or bent because of water hammer issues. The booster pumps on the hot water system had failed and had been changed several times. (This building was about two and one half years old at the time.)
The reason there were hot water booster pumps was because someone decided to try and circulate through pressure reducing valves. Instead of locating the water heaters within the pressure zone, they decided to use large triplex hydronic circulating pumps as booster pumps and they were wasting tons of horsepower trying to push water through the recirculation pumps and check valves. I produced a report with over 200 pages of code violations, poor engineering practices and shoddy workmanship and poor maintenance practices. I felt sorry for the owners in these condos who had paid millions of dollars to live up there with all those problems that they are mostly unaware of. Interesting facts. There is no code requirement dictating how a domestic hot water system should be designed or sized. The codes mostly just require hot water and the codes give temperature limits for certain fixtures but they do not dictate how that is accomplished.
Investigation No. 2 – Bed and breakfast out of hot water
A fella’ called me from a state in the Rocky Mountains. He ran a bed and breakfast and had several rooms that he rented during the peak season. He had a mechanical room that was generously sized. He thought he could add one more room to his facility if he could just remove the water heater in that space. He saw an advertisement for continuous hot water from a tankless heater company. So, he found a nook under the stairs where he could put a tankless heater and he removed the old 80 gallon heater in the mechanical room and converted it into another room. Soon after the conversion, he started getting complaints by the tenants that when more than two people were in the shower, there was no hot water. He called me to inquire about this phenomenon.
I went online and reviewed the tankless heater sizing and installation manuals with him on the phone and pointed out a very important section in the text. The electric tankless heaters he purchased only raised the water temperature 50°F at a flow rate of about 3 gpm. His cold water ranged from 40 to 65°F and averaged 55°F during a good portion of the summer. When he is getting 55°F cold water the tankless heater will provide 105°F hot water all day at 3 gpm. (Enough for one shower at 2.5 gpm or two showers at 1.5 gpm.)
His showers were 2.5 gpm. I suggested using lower flow rate shower heads,1.5 gpm). So that two people could shower at the same time. (As long as there is no other hot water demand at that time.) I said the third shower would probably never work with that tankless water heater. (The laws of physics won’t change, no matter what the salesman tells you.) I suggested a separate tankless heater for the other bathroom.
Investigation No. 3 – Mountain resort with improper piping and unbalanced hot water circulation.
I received a call from a contractor one day who said he had a problem. I inquired further, and he told me a tale that sounded like a broken record. He said he had installed the plumbing on a three-story lodging building at a mountain resort with an indoor water park. The building was only a couple of years old, and pipes were springing leaks everywhere. He said the owner thought there might be a problem with the water quality. The contractor said there was a problem and everyone was pointing fingers at each other. I had an idea of what the problem might be, so I asked a few questions.
First, how big was the hot water return piping out at the ends of the system? He was puzzled why I wanted to know that at first. Then he answered ½ inch.
Then, I asked how big the hot water recirculation pipe was after all the hot water return pipes collected together? Again he was curious why that would matter. He said it was 1¼ -inch copper piping.
Next, I asked him what was the horsepower, flow and head of the circulating pump? Again, he was curious and said he did not know at that moment. But, he installed whatever was shown on the plans. He put the phone down and went to check. He returned shortly and said it was a 3 horsepower pump with 33 feet of head and 30 gpm.
Finally, I thought I knew what the problem was. But I needed to look at the system first to rule out some other things. There was an expert for the engineer who pointed a water quality and lack of balancing. The owner had a balancing contractor who had been tinkering with the system and rebalancing it all along. The owner suspected water quality and possibly a balancing issue. I performed a water quality test ahead of and after the on-site water softeners. Water quality was not a problem. There were several sets of shell and tube heat exchangers that had sprung leaks and there were a couple of experts that seemed to think there was a water chemistry problem because they were corroding near the connection to the tube sheet. The sheet was made of ferrous metal and should have been stainless steel or brass for this application. But, it was not the steel tube sheet corroding, it was the copper tubes.
The patter looked more like erosion to me than corrosion. The erosion was with lots of pitting near the inlet from the tube sheet, and became less as it got away from the tube sheet. This was because water enters the tube flowing around the edge of the tube sheet, and was very turbulent and flowing at high velocities. As the flow makes its way down the tube the vortices and high velocity flow stabilized and there was less erosion further down the tube. It was not a dissimilar metal corrosion issue, because the more noble metal was the metal that was failing.
Reviewing the pumps and pipe sizes the flow velocities 30 gpm in a 1/14-inch pipe produced a velocity of about 8 feet per second, which is about 5 to 6 feet per second higher than it should have been. The original system temperatures were 160°F. The Copper Development Association has a handbook of copper tubing that recommends a maximum velocity of no more than 8 feet per second in copper cold water pipes; no more than 5 feet per second velocity for copper hot water pipes up to 140°F; and no more than 2 to 3 feet per second for copper hot water pipes over 140°F. The leaks all occurred in the ½-inch pipes closest to the mechanical room in the center of the building. The owner’s maintenance staff admitted to adjusting balancing valves and changing out types of balancing valves. These adjustments and changes affected other areas of the building and caused the system to go out of balance.
A plan with all of the leaks indicated they were all close to the mechanical room. After adjustments were made and circulating pump impellers were trimmed, the system began working as intended. The engineer had severely oversized the domestic hot water circulating pump. The domestic hot water system was also designed as an instantaneous water heater system. The normal design is to have a hot water storage tank and with each pass of hot water through the heat exchanger it picks up about 35°F. The normal design would bring the cold water connection to the hot water tank and have a separate circulation pump to circulate hot water between the heat exchanger and the storage tank until the thermostat is satisfied. This piping configuration keeps a constant flow through the heat exchanger and a constant temperature rise in the hot water tank.
Instead, the engineer designed the system where they piped the cold water directly through the heat exchanger. This piping arrangement caused the entire hot water peak system flow to flow through the heat exchanger in addition to the circulated flow. This caused excessive flow velocities in the heat exchangers, and about every year or so they were replacing the heat exchangers. The unbalanced flow caused temperature fluctuations, which caused the maintenance staff to try rebalancing the system and led to erosion in other areas. The moral of the story is do not flow through a heat exchanger with the incoming cold water and watch the flow velocities.
Investigation #4 – Water thermal expansion considerations for pipe material substitution
In a large city in the East, there was a building that was almost 600 feet tall. It was built to take advantage of the views of a mighty river flowing by a mighty city. The building had been specified with 6-inch copper pipe and a value engineering suggestion was put forth to save lots of money by using a plastic material for the water risers. The copper pipe riser was almost 600 feet high. It was substituted for the plastic material that had an expansion coefficient over four times that of the copper pipe. The copper riser needed to have expansion loops in the riser to make up for about 6.6 inches of thermal growth in the copper riser. The plastic pipe had an expansion coefficient of 4.1 times that of the copper pipe.
The plastic pipe material was chosen and installation began in February with plastic sheeting and heaters to keep the installation temperatures just above freezing. The riser was installed and a friction clamp was installed at every floor level where the riser came up through a core drilled hole in the floor. In May, as the temperatures started to warm up, the pipe started to grow and midway up the building the pipe had expanded to where the friction clamps had raised several inches off the floor. This prompted a question that was answered by a resin manufacturer. The manufacturer said that the material was strong and could handle the stress, and they could just re-adjust the riser clamps and re-tighten the clamps.
Needless to say, when they turned on the water heaters and started circulation hot water the pipe grew over two feet in length causing a tee to snap off at a floor near the top of the building. This caused water to flow from a large diameter tee down through the entire building causing tens of millions of dollars in damages. The finger pointing started with the contractor pointing at the engineer and the pipe manufacturer. He put it in just like the drawings, except for expansion loops. The engineer simply approved a material change and did not consider and requirements for additional expansion. The pipe manufacturer had all of these items covered in their installation manual, but no one read the manual. Don’t get all wet. The plastic pipe material would have been just fine if it had been installed in accordance with the installation instructions, but no one checked.
Make sure you check for these types of things. Stay dry, and stay out of hot water. Save water safely.
Ron George, CPD, is president of Plumb-Tech Design & Consulting Services LLC. Visit www.Plumb-TechLLC.com.