Plumbing Forum - November 2000
A Matter Of TasteQuestion: Why does water taste better from a lavatory faucet than from a kitchen faucet?
Julius replies: Your question regarding the quality of water between a kitchen faucet and a lavatory faucet has been one of those mysteries that has been analyzed quite thoroughly. Faucet manufacturers have spent millions of dollars researching the quality of the water delivered from various faucets. We now have a national "consensus" standard, NSF 61, that specifies what the faucet must meet in delivering a given quality of water.
Let me first respond by saying that some people are of the opinion that kitchen faucets provide a better water quality than bathroom faucets. Others claim that the best water is from their water dispenser on the refrigerator, even though the supply comes from the same pipe as the one serving the kitchen faucet.
Believe it our not, the research has proven, rather conclusively, that the water quality from a kitchen faucet and bathroom faucet is the same. There are variations between manufacturers.
However, if you have the same manufacturer for both the kitchen faucet and bathroom faucet, you are getting almost identical water.
This brings us back to, "What is the difference?"
Most people like to drink water that is very cold. The water coming through a refrigerator is cooled inside the refrigerator, hence, it is probably the coldest water available in the home. In the bathroom, the water is often very cold because the person getting a drink first uses the water closet and flushes. This starts the flow of cold water. Then he washes his hands, which continues to flow the cold water. By the time he takes a drink, the water is nice and cold. This fools the brain into thinking it tastes better. (Just think, would you like to taste water that is 100 degrees F?)
As for the kitchen, in most homes the kitchen is located the furthest from the source of water. To keep the cost down, most water meters are located closest to the bathrooms since they have the most piping. By comparison, kitchens have a small amount of piping and can be located further from the meter.
Hence, it takes some time to bleed the water in the piping to obtain the coldest water available. You tend to want a drink immediately, not in three or four minutes. Furthermore, studies of the human body have shown that we can sense the difference of 3 degrees F in the temperature of water.
Water sitting in a pipe for a long time will rise in temperature because of exposure inside the home. (If the thermostat is set at 70 degrees F, the water wants to achieve that temperature.)
Water in the piping located below ground will be approximately 55 degrees F. During the winter months, the temperature can drop to 45 degrees F. That colder temperature is what does it.
Tee-ed OffQuestion: We have been told for years that you cannot install a sanitary tee on its back. Yet when we traveled to a neighboring state, everyone installed a sanitary tee on its back. What gives? Is this OK, or a problem?
Julius replies: It depends. We need to separate whether the connection is receiving waste or whether the connection is for a dry vent. With regard to waste, virtually every plumbing code in the country prohibits a sanitary tee from being installed on its back. I happen to agree with this.
A sanitary tee does not have a smooth pattern of flow that provides a good transition from a vertical drain to a horizontal drain.
While I said that virtually every code prohibits this installation, there is a state code that allows it. You will find the installation throughout that state. You correctly named the state. (I will not.)
As for venting, I have no problem with installing a sanitary tee on its back. Some plumbing codes actually prohibit a sanitary tee on its back for a dry vent connection. There is no justification for this prohibition. I have asked certain code officials why they believe in this restriction. The response was that the vent is often used to snake a drain line. When I point out to them that the vent has vent elbows that prevent a snake from going through, they shrug their shoulders.
Problem DrainQuestion: We have a drain that is being wet vented. The plumber eliminated one of the vents. Now we get a blockage every week. The blockage is when the 3-inch drain connects to a 4-inch, which connects to a 4-inch sanitary tee. Is the reduced amount of venting causing the stoppage?
Julius replies: No, venting would have very little to do with this stoppage. Most likely there is a problem with the pitch of the 3-inch drain. When the flow from the 3-inch drain reaches the 4-inch, the velocity is probably too slow. At the 4-inch, the velocity would be further reduced. Hence, if you drop the velocity before the rate to keep solids in suspension, you have a stoppage.
My recommendation is check the pitch of the drain. If the 3-inch drain has less than 1/8 inch per foot, you are asking for problems. Besides, if you are going to rip out a wall or ceiling, try to guess the right one first.
(Response from questioner: You were right, the pitch was nearly flat. We had the drain re-piped. In the past month, there have been no stoppages. You prevented us from ripping out the wrong wall and ceiling.)
Code QuestionsQuestion: We have noticed that some plumbing codes have suds zone requirements while others do not. Which code is correct?
Julius replies: The plumbing code with the suds zone has the older code requirements. The plumbing codes that have more recently evaluated the suds zone requirements have eliminated the code section. Hence, suds zones are not effective.
There have been a lot of studies done on sudsing in a drainage stack in tall buildings. Suds are caused by a combination of turbulent action, air and high sudsing detergents. If you eliminate one, you have eliminated the development of suds in the stack. If you study the design layout recommended for a suds pressure zone, the layout does nothing to eliminate any of these three items.
The suds zone concept was based on delaying the suds entering the drainage stack. There was nothing in the suds zone to eliminate sudsing. Once the suds zone filled with suds, the suds then entered the drainage stack.
The current theory of suds prevention is the use of low sudsing detergents and smooth pattern fittings. One of the problems, however, is we have no control over the types of detergents sold on the retail level. Hence, the sizing of the drainage stack and the proper use of fittings is very important.
Another means of reducing the creation of suds is by having a drainage stack discharge into a larger diameter building drain. In other words, a 3-inch stack discharging into a 4-inch building drain.
Necessary EvilQuestion: We were informed by the inspector that the penetration of a plastic pipe through a concrete floor to connect to a water closet flange (and water closet) was required to have penetration protection. This seemed rather silly. Is it necessary?
Julius replies: I agree with you, it is silly, however, under the latest edition of many of the building codes, it is required. When penetration protection was first added to the building codes, the requirements had many exceptions. One exception dealt with the connection to a water closet.
While the exception never mentioned water closets, it did address connections that were not concealed in the wall.
If you stop and think about it, if there is a fire on a lower floor, and a plastic pipe burns through, what is exposed on the upper floor? A vitreous china water closet that does not burn. If the fixture happens to crack, then what happens? Well, it is filled with water. Hence, I think it is silly to require penetration protection.
You are probably asking why the building code changed the requirements. The simple answer is that the consultants for the penetration manufacturers got overzealous. Each year, they chipped away at the exceptions. Their means of chipping away was to say, "Hey, there is no fire test data to show that a water closet sitting over an opening with a water closet meets the one-hour rating for penetration protection."
This may sound good, but I believe the question should have been reversed. If you want this requirement, provide actual fire data that shows that there has been a problem with this penetration under actual fire conditions. In other words, if we haven't had a problem, why do we need to add a requirement to the code? I have not seen any data to show that the water closet connection to plastic pipe is a hazard resulting in the passage of fire between floors.
Size MattersQuestion: We have a commercial project with a return circulation pump on the hot water system. The sizing of this pump has gotten very confusing. Between the pump manufacturer, engineer and our estimator, the size has been all over the place from 1/16 horsepower to 1/2 horsepower. What sounds accurate to you?
Julius replies: The 1/16 horsepower sounds accurate to me. You want the pump on a return circulation line to be as small as possible. This pump is designed to just keep the water moving. When I say moving, I mean moving very slowly.
What tends to happen is the manufacturer suggests a small pump; the engineer thinks it is too small and increases the size; the contractor gets the project and assumes the engineer is an idiot because the pump looks way too small. The contractor increases it again. The result is a grossly oversized return circulation pump.
In a year, when the contractor is called back to the project, he wonders why the hot water circulation line is pitted. He assumes it was bad copper and just replaces the piping, maybe this time making it Type L copper rather than Type M.
This is a vicious cycle that will continue in commercial construction. When you have a pitted return circulation line, either the pump is oversized or the piping is undersized. As a result, the velocity in the piping is too high. This will result in what the copper industry refers to as erosion corrosion.
For a return circulation, the flow rate should never be above 2 ft. per second. I tend to keep it around 1foot per second. Hence, a very small pump.
Another thing to keep in mind is that the ideal installation has a continuously operating pump. It makes no sense to start and stop the return pump. You extend the life of the pump by having it continuously operating. Don't think it is an energy waster to do this. A 1/16-horsepower pump is like having a 60-watt light bulb burning all the time. That's nothing in a commercial building.
Cross ConnectionQuestion: Can you use a double sanitary tee (commonly called a cross) to connect two lavatories on opposite sides of the wall? If so, how do you run a snake down the line?
Julius replies: The answer to the first question is "yes." The answer to the second question is "very carefully."
In all seriousness, a double sanitary tee is a common fitting used to connect two lavatories to a vertical drain. Some plumbing codes place limitations on the use of this fitting, such as, you must have the vertical drain a larger diameter than the horizontal drains. These limitations are unnecessary for a lavatory connection.
While fittings are intended to allow for the snaking of a drain, not all fittings make drain cleaning easy. That is why the plumbing codes spell out requirements for so many "cleanouts." I have had to play all sorts of games to get a snake through these fittings. It is not always easy, but it is doable.
The last job where I encountered these fittings, we ran a string through the head of the snake.
When the snake hit the fittings, we pulled on the string to direct the snake downward. Once the snake made it past the fitting, we pulled the string out. Yeah, it would have been easier with a long turn fitting, but then the installation would have violated the venting requirements of the code.
No LimitsQuestion: How far can you really go on a combination drain and vent system before you have to install a vent?
Julius replies: How far do you want to go? Some plumbing codes place arbitrary limitations on the length of a combination drain and vent before a vent must connect to the drain. However, any limitation is strictly arbitrary. In other words, there is no limitation. The International Plumbing Code, which is the most modern of the plumbing codes, has no limitation on a combination drain and vent.
If you have a code with an arbitrary limitation, you need to ask those responsible for the content of the code how the limitation is established. If they are honest, they will tell you that someone made up a number, they guessed.
After establishing this fact, you need to ask why the International Plumbing Code has no limit while your code has a limit. Do the laws of physics differ in jurisdictions that use the International Plumbing Code? Of course not. Hence, there should never be a limit.