ECOURSE DAY 6:
PLUMBING/ MECHANICAL SYSTEMS


TINY HOUSE PLUMBING/MECHANICAL SYSTEMS OVERVIEW 

There are mechanical system options and alternatives out there that will work for just about any sized home, so ensuring that the system you choose has the proper capacity rating (see BTU description below) is essential. In the end, plumbing and mechanical systems, like the electrical system, have to be sized properly for the space and for the needs of the occupants.

MECHANICAL SYSTEMS

Mechanical systems include heating and cooling systems for your tiny home. Depending on where you live, you may not need one and/or the other to live comfortably in your home. If you live in a moderate climate, you may be able to get away with passive heating and cooling. One distinct advantage of a tiny house on a trailer is your ability to move it seasonally to take advantage of nature’s natural heating and cooling. In the summer, you could move your house to a shady spot in the trees and in the winter, you could move it out to an open space that will receive direct solar gain. If you don’t have that option and heating and/or cooling systems are a must for you, then be sure to take the time to research your options and, most importantly, install a system that is sized to your home.


Heater
Heating and cooling systems vary in size, shape, appearance, and efficiency. There are units available in electric, propane, natural gas, and wood (heating only). The system used to rate the level of heating or cooling a unit emits is called a BTU (British Thermal Unit). A BTU is defined as the amount of heat necessary to raise 1 pound (0.454 kg) of water 1 degree Fahrenheit (0.55 degrees Celsius). Calculating your BTU needs is critical and, when you do it properly, it will allow you to choose a unit that will neither burn you out of your home nor leave you wearing sweaters and long underwear through the winter. The same is true for cooling equipment: knowing your BTU requirements is key.

CALCULATING BTUs

• Step 1: Calculate the square footage of the space to be heated. For rectangular or square rooms, multiply the interior length times the interior width for your square footage. Because most tiny homes are really a multi use room (with lofts and smaller private spaces for bathroom), I suggest you calculate the entire house as one room. After all, you won’t be be installing a separate heating system for your bathroom in all likelihood.

• Step 2: For a bare bones assessment of your heating load needs, simply multiply your square footage times 20 BTU. For example, if your home is 221SF, you would need a system capable of providing 4,420 BTU per hour. This does not take into account your climate, your insulation levels, or the ceiling heights in the structure.

• Step 3: Adjust your heating factor to match your climate, insulation and ceiling heights. In general, the farther you get from the Equator, the greater your BTU needs will be. The same is true about your insulation values: the lower the insulation values, the higher your BTU needs. Continuing this correlation, the taller your ceiling, the higher your BTU needs will be. Standard ranges for heating factors are as follows. Low insulation and warm climate = 35 BTU/sf. High insulation and warm climate = 30 BTU/sf. Low insulation and cold climate = 60 BTU/sf. High insulation and cold climate = 50 BTU/sf. As you can see, there is a wide range of numbers. Taller ceilings will impact your requirements as well. For example, all square foot measurements in the standard tables above assume 8’ ceilings. If your tiny house has 10’ ceilings, then you need to scale your BTU rating by at least 1.25 to accommodate the extra head room.

• Step 4: Be sure to include the efficiency rating of the heating system. There are two numbers given on a typical heating system: the input and the output. The input measures the heat that the system generates while the output measures the heat that actually reaches you. As an example, let’s say you have come to a BTU requirement of 10,000 without accounting for the efficiency of the unit and you are planing to purchase a system that provides 80% efficiency. Factoring your numbers by 0.8 will mean that you need a system large enough to provide 12,500 BTUs in order to actually provide the 10,000 BTU you need to heat your space.

• Step 5: Determine your cooling needs. For areas 100-150 SF, one would require 5,000 BTU for proper cooling capacity. For areas 150-250 SF, one would require 6,000 BTU for proper cooling capacity. For areas 250-300 SF, one would require 7,000 BTU for proper cooling capacity. For areas 300-400 SF, one would require 8,000 BTU for proper cooling capacity, and so on.

• Step 6: Adjust your numbers for special conditions. For heavily shaded sites, you can adjust by -10%. For very sunny sites, you should increase your needs by 10%. If you plan to cook a lot in your home, consider adding 4,000BTU to your cooling needs. Even people need to be considered in your calculations, especially in a tiny house. Each person should be considered as 600 BTUs in your cooling calculations.

• Step 7: Consider your power source and the energy efficiency rating of your cooling unit. Cooling can be expensive to run so you may want to consider the use of passive cooling in place of a mechanical system. If you must purchase and install a mechanical system, be sure to get the most energy efficient unit available to you.

PLUMBING SYSTEMS

There are several options available to you for your plumbing lines: copper tubing, PVC/CPVC and PEX line being the most common. Which one you choose will depend on your skill set, your budget, the product availability, and your time line. Let’s take a look at each water supply system to get a sense of which might be best for you. It should be noted that all plumbing lines will need to be properly anchored to the frame with clamps specifically designed for each material. The location and frequency of the clamps will depend on the plumbing codes enforced in your area. Be sure to confirm that all applications described below meet the plumbing code in your area.

Be sure to check with your local building codes when it comes to plumbing materials, and all materials for that matter. In the case of plumbing materials, it is not uncommon for a material to be accepted in one area and illegal in another. For example, CPVC is not code compliant in Iowa for potable water systems; however, it is in Florida. Be sure to know what materials you can and can’t use during the design phase of your construction project so that you don’t back yourself into a corner with no way out.

PVC/CPVC

PVCPVC stands for PolyVinyl Chloride piping and CPVC stands for Chlorinated PolyVinyl Chloride piping. The main difference between the two is that PVC is not designed for use in hot water systems while CPVC is. Using the full name for the pipe makes it sound much more sinister than its acronym and some of you may decide right off of the bat not to use plastic pipes in your water system as a result. This is obviously a choice that you can make; however, keep in mind that almost all of your water is already run in plastic pipe before it gets to your house, so eliminating it from your home will only remove one part of the equation. This is because all modern supply lines for city water are made of plastic as are the lines from modern well pumps.

PVC/CPVC is the least expensive and easiest system to use for your water supply lines. The material is available at all plumbing supply and hardware stores and in many different sizes. Main supply lines to the house, those outside of the home, are typically 1” lines. Most main water supply lines within a home are run with 3/4” pipe while branch supply lines. The ones that go to individual fixtures, are made up of 1/2” lines. All of the fittings are easy to find and even easier to install because all you need is pipe primer and some glue to install your fittings. The installation process is as follows:

PVC Cutter• Step 1: Cut the pipe square to the length of the pipe. An angled cut may result in a leaky joint. There are three common ways to make the cuts. A hacksaw, a miter saw, and a PVC pipe cutting tool. My preference is the pipe cutting tool because it is inexpensive, small, and accurate. Its size allows me to bring it to the pipe rather than taking the pipe to the cut station. It also automatically aligns with the axis of the pipe to ensure straight cuts. A miter saw is my second choice; however, I have to leave the location of the cut to bring the pipe to the saw. This slows down progress. A hacksaw is an option, but it is easy to run off of square with a hacksaw and risking leaky joints is not an option for me.

Deburring tool• Step 2: Use a deburring tool (roughly $20 from your hardware store) to remove all pipe burrs that exist as a result of the cut. Once again, the PVC cutting tool and the miter saw are your best cutting options because they leave very few burrs. If you don’t have a deburring tool, use a utility knife to clear away the burrs.

• Step 3: Bevel the end of the pipe by 10 to 15 degrees. Most deburring tools will provide the correct bevel at the same time that they remove the burrs which makes them a good option for this type of work.

• Step 4: Clean and dry the pipe end that will be inserted into the fitting. Clean and dry the fitting as necessary.

• Step 5: Dry fit the pipe and fitting. It is not only a good idea to make sure that the pipe fits the fitting properly, but it also helps ensure you have cut the pipe to the right length before you attach it to the fitting. Once attached with glue, the only way to get it off is to cut it off.

Primer application• Step 6: Use the appropriate size applicator (roughly 1/2 of the size of the pipe diameter) to apply a generous amount of pipe primer to both the pipe end and the fitting socket. Allow the primer to dry. Note: some glues do not require a primer; however, most do so be sure to check the instructions of the glue you are using.

• Step 7: Use the appropriate size applicator (roughly 1/2 of the size of the pipe diameter) to apply a generous amount of glue to the pipe end and to the fitting socket.

• Step 8: Insert the pipe all the way into the fitting until it bottoms out, turning the pipe 1/4 turn as you insert it. Keep pressure on the fitting for at least 30 seconds to prohibit “push out.”

• Step 9: Remove excess glue from the union. A union that is well made will have a continuous bead of glue around it; however, it will not have excess dripping from the joint.

• Step 10: Be sure to align all of your fittings and pipes so that there is not any strain on them. Measurements need to be accurate and it may take you a few attempts to get the measurements right. That’s okay. Estimating the fitting socket depth is the most common place for mistakes. Once you figure it out, the rest is relatively easy.

COPPER TUBING

Copper tubing has been used for a long time in residential construction. It is a great system in homes built on a foundation, but I would not recommend it in a structure that will experience excessive vibration, such as a tiny house built on a trailer. The materials are readily available at hardware and plumbing supply stores; however, they are more expensive than PVC/CPVC piping. The fittings are attached by a process called soldering which is fairly labor intensive and takes some specific skills to be able to execute properly. The installation process is as follows:

• Step 1: Identify the correct material for your project. There are four different grades, based on tubing wall thickness, for copper tubing which are identified with color coding. The two you need to consider are type L and type M. Type L is the most common and is marked with blue to identify it. Type M has the thinnest wall thickness allowed for pressurized systems and is marked red. For simplicity, plan on using type L throughout if you plan to use copper.

Copper cutter• Step 2: Cut the tubing to length using a tube cutter. Be sure to cut the end square.

• Step 3: Use a deburring tool to remove any burrs produced during the cut.

• Step 4: Remove the copper oxide coating on the outside of the tubing and the inside of the fitting with a sanding cloth designed for use with copper soldering.

• Step 5: Clean and dry the tubing and fitting completely making sure they are free of dirt, grease, water, oil or other imperfections.

• Step 6: Brush the surface of the tubing, the inside the tubing where it meets the fitting, and the inside of the fitting itself with solder flux.

• Step 7: Assemble the fitting and tubing together making sure they fit snugly and completely.

Soldering• Step 8: Use a blue flame from a soldering torch to heat the surface of the union. At the same time, apply a lead free solder stick to the opposite side of the joint. When the temperature reaches the right level, the solder will run towards the heat and fill the joint. Continue to feed solder into the joint until it has completely circled the union while being careful not to overheat the copper. Constantly move the torch from side to side in the process. Do not leave it in one position for too long as that will overheat the copper.

• Step 9: Wipe excess solder off of the joint and spray the union with a mist of water to tighten up the joint.

• Step 10: Be sure to flush the water supply system with potable water to remove excess flux before using the water.

PEX LINE

PEXOne of the relative newcomers on the plumbing scene is PEX piping. PEX is the common name for cross linked polyethylene, and once again the acronym sounds much more pleasing than the full name. There are some big advantages to using PEX lines in a tiny house, especially one on a trailer. It is extremely flexible which means that movement in the structure is easily absorbed by the lines, making them stronger and more resistant to breakage. The flexibility also allows for extreme expansion of the pipe. This translates into levels of protection from burst pipes due to freezing not available in other pipe materials.

PEX line comes in long rolls, 50’ and 100’ are the most commonly available lengths, so long runs can be made without any joints or couplers. When joints are required, there are two main options to complete the process. One is using a flaring tool and crimpers. The other is to use a proprietary system called Shark Bite in which no special tools are required other than a deburring tool specific to PEX lines and Shark Bite fittings. The Shark Bite system is extremely easy but more expensive than the standard flare and crimp operation. The installation processes are as follows:

Flare and Crimp:

• Step 1: Run the water lines to the general location of the fittings. Leave extra line at both locations (where the line is coming from and where it is going to) as you will need to make exact length cuts in the future.

PEX Installation• Step 2: Install the copper fittings that will be used as the points of attachment for your sinks, shower, toilet (if applicable) and other point of use items. The fittings will need to be attached to the frame, typically via blocking provided for that specific use.

• Step 3: Cut the pipe to length square to the pipe and deburr the end of the line accordingly.

Screen Shot 2014-03-16 at 9.22.10 PM• Step 4: Slide a crimp ring onto the pipe and then insert a PEX flare tool into the end of the line to gently expand the opening. This makes it easier to slide the PEX line onto the fitting to the appropriate depth. The PEX should slide onto the fitting to the shoulder line identified on the fitting.


Crimp ring
• Step 5:
Move the crimp ring into position on the fitting. This is crucial. The crimp ring has to be no less than 1/8” and no more than 1/4” to the end of the pipe to ensure a solid joint.

• Step 6: Position the crimping tool over the crimp ring so that it is entirely covered by the tool and close the jaws as tight as you can.

Shark Bite:

• Step 1: Run the water lines to the general location of the fittings. Leave extra line at both locations (where the line is coming from and where it is going to) as you will need to make exact length cuts in the future.

Deburring tool• Step 2: Cut the pipe to length square to the pipe and deburr the end of the line accordingly. Use the Shark Bite specific deburring tool as you will also use this as a depth gauge for your PEX line.

• Step 3: Mark the PEX line where it meets the collar of the deburring gauge. This line represents the proper depth for the pipe to be inserted into the fittings.

PEX installed• Step 4: Press the pipe into the Shark Bite fitting until it reaches the marked depth on the pipe. If it does not reach the full depth, use the removal ring (an inexpensive, specialty item for Shark Bite fittings) to pull the line from the fitting. Ensure that the center, “inner pipe” inside the fitting is landing properly with the PEX line and reinsert the pine to depth.

That’s all. It’s really that simple!

You’re doing awesome! The final lesson tomorrow? Framing and roofing. 🙂

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