Plumbing in manufactured homes is a bit different than plumbing in a site-built home but the basics are the same. This article will help you learn how manufactured home plumbing differs from a site-built house, how to find what’s wrong with your plumbing system, and how to repair the most common issues.


Wrong Information about Manufactured Home Plumbing Isn’t Hard to Find

One popular home improvement site erroneously states that mobile homes aren’t regulated as well as a site-built home and that their plumbing systems are made of cheaper materials than most site-built home.

However, manufactured housing has been on the cutting edge of plumbing technology for decades. In fact, PEX was originally used in manufactured housing long before the site-built construction industry began using it.

It’s no secret that manufactured homes have to meet stringent national regulations and be inspected before leaving the factory by certified inspectors.

That’s just one example of the outright wrong and overly negative information you’ll find about manufactured homes across the web. This article will help you understand the how a plumbing system works in manufactured homes and how to troubleshoot common plumbing issues.


Plumbing in Manufactured Homes Vs Site-Built Homes

Plumbing in manufactured homes has the same basics and logistics as site-built homes. The main differences are the location of the pipes and the ‘simplification’ of the system. Location is different simply because manufactured homes are built differently. The other big difference is the lack of cleanouts and cutoff valves in the home but newer manufactured homes have those now.

Supply Line Location 

The most obvious difference between site-built home and manufactured home plumbing is the location of the supply lines. Supply lines are where your water comes from and in site-built homes, they are run inside the walls. In manufactured homes, they are run under the home either in the middle alongside your heating ducts or on the side, depending on the layout and location of your water heater.

remodeling your manufactured home bathroom - mobile home bathtub info 04


Cleanouts, Overflows, and Traps

Cleanouts, overflows, and traps are not used much in manufactured homes.



Ventilation is as important as supply and drain lines in all plumbing systems so of course manufactured homes have them – they are required by law!
Vent stacks are the small pipes sticking out of your home’s roof and they help remove all the bad fumes and gases that are created from waste away from your home. You have to have one for your plumbing to work properly.


Cheaper Material?

As stated above, some people believe manufactured homes have a substandard piping material and that is just not true. There were as many site-built homes with those pipes as manufactured homes.

Some manufacturers did use the plastic, polybutylene) pipe or galvanized metal pipe, which was standard at the time but it was later learned that the material had issues. We’ll talk about that in detail in a few moments.

Cutoff Valves

It is smart to have cut off valves at every water source (faucet, tubs, and toilet) however, if you have to repair or replace a supply line anywhere within your home, you must cut the main water supply off. There’s a lot of pressure in those lines and it needs to be reduced before you start cutting into them.


3 Parts of Manufactured Home Plumbing Systems

Basically, there are 3 parts that make up the whole plumbing system. Supply lines do exactly what they say they do,  supply the water. The next component is the drainage lines and they drain waste. Simple enough, huh? The last part is the ventilation lines.

Your water supply lines are the smaller pipes (3/8-1 inch) that come into the home. They are usually either copper or Pex. If your home has white, cream or a medium grey pipe for your supply lines, you will probably want to replace them as most local regulations don’t recommend them and some have banned them altogether. The water comes through 1 line and then branches at the water heater so some water can get heated, from there a hot and cold line runs parallel to the faucets, tubs, etc.

Your larger pipes (2″-4″) will be your drain lines. Drainage lines use gravity, traps, and ventilation to ensure the optimum waste removal and keep gases and fumes from building up and releasing. Think of this as a completely closed system with positive and negative vacuum or pressure. All the parts have to work correctly to allow the system to do what it is designed for. Without the proper positive or negative pressure acting as a vacuum in the pipes the waste won’t go where it’s supposed to, it can back-flow instead.

Drain pipes are usually made from copper or PVC.  You have to get the grade right on drainage pipes because too much of a grade (or slant) will cause as much issue as too little. A 1/4″ to 1/2″ grade per every foot is ideal.


Ventilation Pipes

Ventilation pipes ventilate and help the waste keep the proper pressure or vacuum – in other words, it keeps water in all the right places.  It is just as important as the supply and drain lines and you have to have ventilation in order to make it all work. Plumbing systems are much like a living thing – it has to have air and water.

A single ventilation pipe in a manufactured home won’t help the drain pipes furthest away so they use what I’ve always just called a dry vent (they also call them auto vents, check vents, or air admittance valves). These vents allow air to flow into the drains. Keep in mind that oftentimes a dry vent on a sink isn’t necessarily helping the sink it is tied into, it’s benefiting the other drains in the house. If you would like to learn more about auto vents, this article does well explaining, as does this one.


check vent



Remember that water is coming into your home under a lot of pressure through your supply lines. It can turn corners and go up several stories. If you have a leak in the system, imagine how much water can be lost in just a small amount of time! It really pays to be proactive and do a monthly plumbing check. Drainage leaks are sneaky little things. Water will always follow the path of least resistance so sometimes it’s hard to pinpoint where the leak is coming from.
Here’s the simplest schematic I could find to show you:


Common Plumbing Pipe Materials Used in Manufactured Homes 


You will need to know what type of pipe and fittings are used for each sub-system. There are basically 2 types of piping used in plumbing- metal and plastic. Most plumbing in manufactured homes uses plastic. Plastic pipes include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), PEX pipe and PolyPipe®.  Metal plumbing pipe consists of copper, stainless steel, and galvanized steel. Not all pipes are as useful or effective as others, and each type is used for a specific purpose in plumbing.


Polybutylene Pipe

Polybutylene was used in all types of homes, including manufactured homes, from the late 1970’s to the mid-1990’s. Several lawsuits were filed on behalf of millions of homeowners due to issues this material had. If you had any type of bleach in your water, and most city systems do, the pipe would break down and cause leaks and complete blowouts, usually within 5-10 years. You can’t buy it anymore but it’s still in more homes than it should be. It’s a medium grey color and will have PB and some numbers on the side. If you have this in your home today, you need to replace it and then go buy a lottery ticket cause you have been very lucky to have had it this long without any issues!

If you are looking to buy an older manufactured home, do not buy it with this kind of pipe in it. Make the seller replace it or have them take the replacement cost off the price of the home (there may even be local and federal laws prohibiting the sale of a home with this type of pipe in it).


PVC is a type of plastic plumbing pipe primarily used to transport high pressured water. It is available in several standard sizes, ranging from ½ inch to 4 inches in diameter. PVC pipe is only made to handle cold water, as hot water will cause the pipe to warp. It is generally white in color, though a few varieties are gray.


CPVC pipe that has received an extra chlorination. It comes in a distinctive yellow color and can handle both hot and cold water. CPVC is more flexible with substantially thinner walls than PVC pipe and has the same outer diameter as copper pipe, which increases its range of uses.


PEX, also known as cross-linked polyethylene pipe, was first manufactured in the 1920s but has become more popular in recent years. It shares the same outer diameter as copper and can be used for both hot and cold water. However, PEX pipe has a much higher heat resistance than most other plumbing pipes and is often used in water-based heating systems. It comes in a creamy white color, as well as red and blue which is used to denote hot and cold pipes respectively.  


mobile home plumbing


We recommend you replace your water lines with PEX when the time comes to update. You can use special fittings to secure the connections by hand or rent the tool needed to connect the lines. Pex, in our humblest of opinions, is the best pipe for water supply lines and is so much easier to install than anything else.



PolyPipe is a thick black pipe used to transport highly pressurized water, usually to and from the home. It is used almost exclusively outdoors and is usually buried underground to prevent freezing. PolyPipe® is extremely rigid, and is rarely used for other purposes.

Here’s a good video about a double wide re-pipe:


Copper is the most common type of plumbing pipe used in the home, although it is more expensive than plastic piping. It is especially resistant to corrosion and can withstand high temperatures. Copper pipes come in three different sizes – type M, L, and K. Type M have very thin walls, while type L is of medium thickness, and type K is the thickest of the three.


Stainless steel

Stainless Steel pipe is less not as commonly used as other metal pipes, as it is more expensive and harder to find. It is primarily used in marine environments because it can withstand salt water, which would erode most other metal pipes. The price makes it less desirable for other applications, or in safer areas where a copper pipe would perform just as well.



Galvanized pipe is known for rust issues and the plastic piping (polybutylene) are known to corrode and cause leaks. There’s also an issue with the connections. If you find yourself plagued with leaks, go ahead and re-pipe the home, if possible.

Galvanized pipes have been used in homes for years, typically to carry water in and out of the house. The galvanized coating prevents rusting and gives a dull gray appearance. Use of these heavy duty pipes is diminishing, as it is being replaced by PEX pipe, which is less expensive and just as durable. Galvanized pipes typically come in sizes between ½ inch and 2 inches in diameter.


Common Plumbing Issues in Manufactured Homes

Nasty smells and weird noises

Notice the yellow vent lines in the schematic above? It’s the small pipe sticking out of your roof. There are wet vents and dry vents, the roof pipe is considered a wet vent. Without proper ventilation, you will encounter several issues. The worse being nasty fumes and a build-up of gases that could cause some serious issues.

Ventilation makes your pipes remain at a neutral pressure. Without proper venting your drainage slows and the water in your P-trap goes away, which in turn releases the nasty gas/fume combination.

If you hear weird sounds coming from your walls you most likely have a venting problem. Think of a soda bottle: when you tip it half way, the liquid smoothly flows but when you turn it completely upside down, it makes gurgling sounds and the soda pours out slowly. That’s what happens when there’s not enough ventilation or air flow. If you have ventilation issues you can fix it yourself fairly easily.

moisture problems in manufactured homes - bathtub leaks



Water is one of the most destructive forces on earth. It will always flow the path of least resistance. Plumbing in manufactured homes will rarely be inside a wall so you won’t need to worry too much about damage to walls, it will be the floors that get the most of the damage and then just spread from there. Most plumbing pipes run under the home and up through the floors.

A monthly check under your home is a good idea. Your flooring is most likely made of a composite wood and that stuff loves water – it just soaks it right up and eventually bows and rots.< In the end, it will be far cheaper, and less stressful, to just run new water supply lines than trying to fight with old material and patches. Area plumbing codes will be the ultimate factor in deciding what material to use but Pex is a popular product and as long as the connections are high quality and a proper seal is made, will be your best choice for supply lines.


Fixing Plumbing Problems in Manufactured Homes

Leaks, clogs, low pressure, obnoxious odors and having no hot water are just a few of the issues that you may encounter. If your manufactured home is older you may have to replace the system entirely. There’s lots that can go wrong! We’ll try to cover them all in the future.


Leaking Faucets

Leaking can occur in a couple of different places on a faucet. It’s probably easier to just replace the whole unit than repairing. If you are especially attached to your faucet, this article about fixing leaking faucets should help.


Clogs in your kitchen Sink

If there is a clog in your sink, a plunger can work well. They make a smaller plunger for the task. If you have a two-sided sink, close off one side by stuffing a rag into the drain (cut off air) and plunge the other side, then switch – keep doing it until the clog is gone.

If you have clog issues frequently, it may be time to find the underlying issue. You can remove your p-trap, if it’s closed off with grease you can clean it out or replace. You may need to add a dry vent to the next closest sink.


How to Turn Your Water Off

You need to know where and how to turn your water off in case of an emergency, or before any repair. Being able to shut your water off quickly can be the difference in a complete disaster and a small inconvenience.  The main stop valve should be around your outside garden hose water connection (hose bib as some call it) and most are easy to get to on a manufactured home.

If you can’t find your connection, then you need to be able to cut your water off at the source: at the main water meter (assuming you are on a city system) or in your pump house if you are on a well system. If you are on city water you will need to own a water meter key in the shape of a five-sided pentagon to remove the cover. They come in different sizes so make sure you buy the right one. You can also use a wrench and long screwdriver for a makeshift key – place a wrench on the vertical (or straight up and down) and the thread the screwdriver through the hole at the end of the wrench. The two tools will look like a T. Use the screwdriver to turn the wrench. This article about turning off your water supply is handy if you want to read more.


plumbing in manufactured homes -

The red arrow shows the nut you need to turn.

Hiring a Plumber for you Manufactured Home

If you do need to call a professional plumber, my best advice is to ask every plumber, and any construction worker for that matter, if they actually passed the licensing exam or if they were grandfathered in. If they say they were grandfathered in, get a different plumber. I’m serious.

Allow me to explain: Here in WV, and a couple other states I know of, they made it mandatory that anyone working on a construction site had to carry a license. They offered 3 types of licenses: apprentice, journeyman, and master. However, when the law first took effect, they gave everyone a time frame to apply and the applicants automatically received the license so one had to take an exam to prove their knowledge.

Now, several states have hundreds of ‘licensed’ master carpenters, electricians, and plumbers that aren’t as knowledgeable as they should be.

Most importantly, ask for references and actually call and ask them how the job went.

We’ve covered the basics of plumbing in manufactured homes: how the systems work, where everything is located, and what your choices are for pipe materials. We also covered the 5 most common mobile home plumbing issues and how to troubleshoot them.

In Part 2 of our manufactured home plumbing series we cover  Ventilation and Drainage Issues

Thanks so much for reading Mobile Home Living!