Ask The Experts

Plumbing & Water Heating

My water heater is making popping sounds when it heats the water. What does this mean, and does it need to be repaired or replaced?

The sound that you are hearing is due to mineral or “lime” buildup on the bottom of the tank in the water heater. Some of the water in the tank becomes trapped in the “lime” and pops as the heat from the gas flame causes water vapor bubbles to form and then release. The popping, sometimes referred to as burping, is essentially harmless. However, the mineral buildup acts as an insulator and reduces heat transfer from the gas flame to the water, resulting in decreased water heating efficiency. Excessive lime buildup probably indicates that your water heater is getting on in years and may be due for replacement. In this time of increased energy costs, being pro-active about updating an older water heater is probably a good idea. Eight to fifteen years life is normal for standard gas water heaters. If you don’t know the age of the unit, the year built can often be found in the first two digits of the serial number, and you may find an ANSI code year on the data plate that could give you a rough idea of its age.

We suggest checking the water temperature at your taps. You may be able to lower the water temperature in the heater which can reduce the amount of burping that occurs, as well as save energy costs, and help prevent scald hazard.

While it is too late for your present water heater, it is recommended with new units that you drain off some water at the tap at the bottom of the tank every few months to help reduce buildup, and some of the newer water heaters are designed to be self cleaning.

We would also suggest having your water tested for hardness. It may be appropriate to install a water softener to reduce the concentration of minerals in your water. This will increase the life of your next water heater, protect your plumbing, and improve the effectiveness of your detergents, soaps and shampoos.

My plumber says that I need to have my chimney relined for the gas water heater to vent properly. Why would this be necessary?

Your water heater uses the chimney to exhaust the fumes produced when natural gas is burned to heat the water. These exhaust fumes often contain carbon monoxide, a deadly odorless gas. Older masonry chimneys can deteriorate, causing debris to block the flue and prevent the exhaust from the water heater from rising up the chimney and out of the house. If your house is 100 years or older, there is a good chance that the chimney has no liner whatsoever. The liner is typically a series of 8 to 12 inch diameter clay tile tubes stacked up through the open core of the chimney, which protects the brickwork from the deteriorating effects of the exhaust gasses. Any unlined chimney, whether used by gas, oil, or wood burning equipment should be lined. But we suspect that the issue in your case is a different, increasingly common, occurrence, caused by the installation of new modern furnaces. High efficiency furnaces extract so much heat from the combustion process, that the exhaust is too cool to naturally rise up a chimney, so they are typically designed to exhaust out the side of a house, using a blower to force the exhaust gasses out. This leaves the water heater, which used to share the chimney with the older furnace, as the only appliance still using the chimney. Now the water heater alone cannot produce enough heat for a natural draft up the old chimney to work reliably. Consequently, we need to downsize the chimney flue by relining it, usually with a 3 or 4 inch diameter flexible metal liner. This is not terribly expensive and well worth the cost. You can check to see if your gas appliance is drafting properly by holding a small mirror up to the opening in the little hood at the top of the unit where the exhaust is ducted to the chimney. If the mirror fogs up when the water heater is operating, exhaust is coming out. Take immediate corrective action. And make sure your carbon monoxide detector in on the job.

I had understood that water heaters should be set as low as feasible to prevent scalding, but recently was told that this can cause bacteria growth. What do you recommend?

We have always recommended that tank type water heaters, whether heated with oil, gas, or electric, be set at a temperature range from 120 to 130 degrees to prevent accidental scalding and to save energy. The problem is that these temperatures can support the growth of bacteria in the water heater, specifically legionella pneumoniaphila sero-group 1. You may remember hearing about a potentially serious illness caused by this bacteria, commonly referred to as legionnaire’s disease. You don’t contract the disease from drinking or bathing in the water, but rather from breathing the tiny water droplets as the water is aerosolized, especially during showering. Estimates of the number of deaths attributable to showering in water containing this bacteria vary widely, but 10,000 per year is a commonly heard number. The generally accepted safe temperature to prevent the bacterial growth is a minimum of 140 degrees. Unfortunately a serious scald hazard exists at this temperature. So, what to do?

The solution is to set your water heater for 140 degree water or higher, and to install a mixing valve. In its simplest form this consists of a valve between the cold water and hot water pipes at the water heater that allows a measured amount of cold water to mix with the hot after it leaves the water heater, thus moderating the water temperature before it reaches the fixtures in the house. Some modern high tech water heaters have digital temperature read-outs, and the better mixing valves are thermostatically controlled. These will provide very reliable safe temperatures. But, installing a simple temperature gauge on the hot water pipe off the water heater and using a thermometer at the tub spout should allow you to adjust a basic water heater and mixing valve appropriately to ensure safe use.

I am building an addition on my house and am considering using PEX tubing for the water supply. Have you found any problems with this type of water piping?

Cross linked polyethylene flexible tubing or PEX is an increasingly popular product for use as water supply piping, or for hydronic heating systems. While this piping was introduced in the U.S. in the 1980’s, it has only recently begun to take over the market. PEX has the advantage of its flexibility, general ease of installation, and, as with most plastic piping, resistance to corrosion and many chemicals. It is competitively priced compared to copper, and also doesn’t have the same sweating problems as copper during high humidity. We have not found a history of problems with this product, although insufficient time has passed from its introduction to know about its long term performance. In any case, from our experience, trouble free operation of any product depends primarily on proper installation, and buying top of the line materials.

The weak link with most piping is the joints or connections. Unfortunately, there are many different types of connectors available, and some may eventually be found to be better than others. With PEX, the common method of installation is to use a manifold, instead of numerous branch fittings, to direct water to the many fixtures in the house. A manifold divides one large supply pipe into many smaller pipes at one location, reducing the overall number of fittings, and making any repairs at the connections easier to complete. In addition to connectors, the other potential problem with supply piping installations is the adequacy of the clamps or hangers. Flexible plastic piping must be well supported, (every thirty two inches), but should not be over-supported. All supply piping, but especially plastic piping, must be able to expand and contract with temperature changes. Excessive or overly tight clamps can prevent movement, resulting in damage or leaks. In our experience, plastic clamps usually fail if used for metal piping, and metal clamps are damaging to plastic piping. The best advice we can give is to only use parts supplied by the manufacturer of the piping, and to follow the manufacturer’s instructions to the letter. And, don’t forget to make sure your installation complies with any local codes.

I have a large family and run out of hot water way too often. Is there anything I can do besides replace my water heater?

We can suggest a few ideas that might help you to avoid buying a larger water heater, by either getting more hot water from your existing equipment, or stretching the hot water that you already have. The simplest solution would be to turn up the water temperature so less volume will be necessary. On most gas fired water heaters you will find a simple adjustable temperature dial located right above the burner area. There is also usually a temperature dial on electric or oil water heaters, but you will probably have to remove a cover for access, and use a screwdriver to make the adjustment. Be careful of exposed wiring connections in the vicinity of the thermostatic control on an electric water heater.

The problem with turning up the temperature is that you increase the risk of scald hazard. Use a thermometer to check the tap water temperature. 140 degrees would be an absolute maximum, and lower would be better. You can also insulate the hot water pipes in the house to reduce heat loss. This will result in more hot water at the taps. It may help to install low flow faucets, or flow restricters in the sink spouts and at shower heads. These simple devices can reduce the total volume of water being used, saving hot water in the process.

If these measures aren’t enough, you may want to consider adding a 2nd water heater, rather than replacing the existing unit. This would be especially true if the demand for hot water varies over extended time periods. If the problem arises when the relatives visit, the 2nd water heater could be turned up when the company comes, and turned down when they leave. The water heaters should be installed in series, so cold water flows through one and then into the other. Water heaters installed in parallel may mix water of differing temperatures together at fluctuating flow rates, resulting in uneven temperatures at your shower head. With the water heaters in series, the first water heater in line can be shut down during periods of low demand. The water will warm somewhat in the first tank just by absorbing some heat from the utility area before moving on to the active water heater, saving you a little more money.

I have city water but my water pressure is getting really poor. How do I know if this is my problem or is a problem in the street?

It is likely that you have a problem with your water volume, not your water pressure. The water pressure from the city is generally constant over time, but a constriction within the pipes is preventing adequate flow or volume for you. If the flow is good for the first few seconds when you turn on the faucet, but then drops off, it is a volume problem and constriction is the cause. It is always a good strategy to look for and eliminate any restrictions that will be cheap and easy to fix first. Check to make sure that you don’t have a long forgotten water filter, or unused but not bypassed water softener, lurking around the area where your water pipes enter the house. These could be clogged. Sometimes a defective main shut-off valve will cause a flow restriction. And check to make sure the main valve is fully open. If your water pipes are copper, these are the most likely culprits. However, if you have old galvanized steel pipes, characterized by a dull gray color and threaded fittings at the elbows and couplings, the problem is probably corrosion and mineral build-up in the pipes. This is very common in houses built before 1950.

You’ll want to determine if the constricted piping is in the house or between the house and the main in the street. Presuming that all your faucets in the house have generally poor water volume, look for an exterior water spigot that comes off the main service as close to the meter as possible and try the volume at that spigot, opening a faucet in the house at the same time. If the flow at the exterior spigot is poor, then you probably need a new service from the street to the house. Unfortunately, that’s your pipe coming from the main, so it will be your expense for replacement.

There are some older houses in the area with original galvanized steel water pipes and services that still have good volume and many more years of life, but far more often the flow is poor and getting worse. Very often the corrosion isn’t just on the interior of the pipes either. Visible rust spots and active slow leaks are likely when pipes of this age remain. After decades of service it’s probably time to replace the old pipes.

I have baseboard hot water heat in my house, and I need a new water heater. A friend is recommending an indirect water heater, rather than just installing the same type I already have. Does this make sense?

We presume that your present water heater is a tank type unit, operating as a separate appliance from your boiler. It heats the water using electric elements, or a gas or oil burner. Water heaters of this type tend to deteriorate rapidly and have a limited life, averaging between eight and fifteen years, because the constantly changing heated water and hot surfaces in the unit cause mineral buildup and are corrosive to varying degrees, depending on the character of the water. Indirect water heaters avoid this problem.

Indirect water heaters are warmed by the same boiler water which circulates through the baseboard heaters in your house. A separate zone is installed to pipe the boiler water through a coil in the indirect water tank, heating the domestic water, in the same way that your baseboard hot water fins heat the air in your rooms. A thermostat in the indirect water heater simply tells the boiler to circulate some of its warm water through the water heater tank as needed. Boilers last much longer than conventional water heaters because they are not constantly taking in fresh water. The water in your boiler system becomes neutralized and non-corrosive. Your indirect water heater may last as long as your boiler, which can be thirty years or more. As an added bonus your indirect water heater won’t require a chimney or sidewall exhaust, since it isn’t burning any fuel, and the unit can be better insulated and will retain more heat, since the heat won’t be escaping up the chimney.

Before making this change though you should determine the capacity of your boiler to ensure that it will be capable of taking on the added load of heating your domestic water as well as heating your house. Most older boilers were oversized to begin with, and most older homes have received upgraded insulation, resulting in excess boiler capacity, but it pays to have someone do the calculations to make sure.

The hot water at the sinks and tub in my house is too hot. I get the hot water from the oil-fired boiler, not a separate water heater. How do I adjust the temperature down without affecting the heat for the house?

Everybody should be as aware of the temperature of their hot water as you are. We recommend that all of our readers put a thermometer under their hot water taps and directly measure the temperature of the water. It should be 120 degrees or lower for greatest safety. Temperatures above 120 degrees can quickly result in scalding. Most gas water heaters have a simple round dial on a small control box near the burner area, with hash marks and settings from WARM to VERY HOT. Oil and electric water heaters are more likely to have a small dial below a removable cover or covered box, with a screwdriver slot for adjustment, and numeric temperature settings. Any of these types of thermostat controls should be easy to adjust to a safe temperature. However, water heaters often get turned up too high because they fail to deliver enough hot water at a more appropriate safe temperature setting. If a safe temperature does not produce sufficient hot water, it may be necessary to install a new water heater with a larger amount of water in storage to make up for the lower temperature.

In your case the situation may be a little more complicated. You probably have a boiler with a domestic coil immersed in the boiler tank. The water is heated as it flows through this tubing or coil within the boiler. The water coming out of the coil will be the same temperature as the boiler water, which is normally 140 degrees to 180 degrees. The only way to properly adjust the temperature is to mix some cold water back in with the hot water before it gets to your fixtures. This is accomplished by an adjustable mixing or tempering valve. This valve will be located close to the boiler and will cross between the cold water supply pipe and the hot water pipe coming off the domestic coil. If you don’t have a mixing valve, you will have to call in a heating contractor or plumber to add one. In any case, it will be well worth the modest cost to keep you safe.

I recently replaced a leaky pressure relief valve on my gas water heater, and now the new one is starting to leak. What could be causing this?

Pressure relief valves are a critical safety device for water heaters, whether the water heater is gas, oil, or electric. If a burner or electric heating element were to fail to shut off when the water reached the appropriate temperature, the hot water would eventually hit the boiling point, creating steam. Steam is incredibly expansive, taking up over a thousand times more space than water, resulting in extreme pressure, if not properly dissipated. Think of what happens in a pressure cooker, and imagine what could happen if the steam had no way to release. An exploding water heater could level a home.

Pressure relief valves rarely leak due to age alone. In fact, as they age they become less likely to release properly when needed. According to a leading manufacturer, they ought to be replaced every four years. While we’re on the subject, modern pressure relief valves are also designed to be temperature sensitive, and should be found in the appropriate fitting on the water heater body, either on the top or the side of the unit close to the top. The device is easy to recognize with its manual release lever on the top. There will be a threaded fitting available on the valve to allow the required installation of an extension pipe. Being sprayed with scalding water would not be desirable if the valve should release, so check to see that the outlet has been extended to be close to the floor.

You should monitor the operation of the water heater to ensure that the unit is not running too hot, but the most common condition that would cause pressure relief valves to repeatedly fail is water hammer. If you sometimes hear a bang in the pipes when a faucet, toilet, washing machine, or some other device shuts off the water, you have water hammer. The surge in pressure as a moving column of water abruptly stops can cause a release of water from the pressure relief valve that then becomes chronic as the valve fails to reseat adequately. A plumber can install small devices in the water lines that provide a cushion of air to stop the water hammer and prolong the life of your pressure relief valve.

I am getting a strong foul odor from my bathroom sink when I run the water. I’m sure it isn’t the tap water. Where is it coming from and what can I do to prevent it?

You are having a vent problem. If you look around at the houses in your neighborhood, and, hopefully your own house also, you will see one or more pipes poking up through the rear roof. These are vent pipes for the plumbing system. These vent pipes, in conjunction with “traps” below your plumbing fixtures, prevent sewer gases from entering the house. Traps provide a barrier of water that sits in the drain pipe to prevent air from the pipes from coming up the drain. Vent pipes allow the air in the waste pipes in your house to vent to the atmosphere to balance the flow of wastewater. When you run water in your sink it fills the drain pipe, displacing the air that was already in the pipe. If the vent pipe is missing, mislocated, or clogged, the only way the air can get out of the way of the water is to bubble up through the trap below your sink and into the room via the drain. Since your drains flow to the sewer system, or a septic tank, these odors are not only objectionable, but unhealthy. There are two other signs of improper venting. If the fixture drains very slowly until it “burps” or some bubbles pop out of the drain, it is another manifestation of the same problem of displaced air. If you hear a repeated “glugging” sound after the water drains out of the bowl, this would be caused by air being pulled into the drain pipes through your sink trap to fill the vacuum created behind the water as it flows to the sewer. A properly vented drain will enter the wall below the fixture to allow a vent pipe to attach to the drain near the fixture, rather than drop through the floor, leaving the vent pipe too far away to be effective. If the vent pipe is missing, or if it is too far away from the affected fixture, call your plumber. If it is more likely that a properly installed vent pipe is just clogged, a sewer cleaning company may be more appropriate.