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Installation of Self-contained Composting Toilets

Vent Stacks

One of the main tasks is the installation of the vent stack, which is included with all units. The vent kits included in the shipping carton are sufficient for installation in most single story buildings. If more is needed they are normally easy to find. All vent pipes are thinwall PVC.


 
Venting Diagram
 
 
The left diagram above shows electric Excel, Compact, or SpaceSaver venting. The right diagram shows possible Excel-NE venting - the 45 degree configuration is dotted because it can only be installed this way when a 12 volt fan is in the stack.
 
 

The drawing above illustrates some of the more common vent stack configurations for self-contained system installations. Electric units with 2" stacks should have the minimum number of bends, should use 45° elbows where possible, and should not have bends totaling more than 360°.

It is very important that self-contained model vent systems do not contain ANY horizontal runs or downward slopes on the pipe.

2" SpaceSaver/Sun-Mar Mobile vents and especially 4" Non-electric vent stacks should be installed as straight as possible. If 45° elbows are needed in a 4" vent stack, a 12 volt fan should be included in the installation to assist airflow.

Merging a Sun-Mar vent with other existing vents risks interference and is not advised.

The diffuser included with all units is a simple but effective device originally patented by Sun-Mar principals to aid updraft, resist winter freeze-up, and protect the vent from downdraft and weather. As shown in the drawings they should be installed 2-3 feet above the peak of the roof for best performance. This prevents downdraft.

Vent joints within the bathroom should be siliconed, vent joints outside should be glued with CPVC glue.

See the Winter Use section for additional tips on protecting your vent stack in the winter.

Detailed Vent Stack Installation Instructions

Electric Unit (2" and 3") Piping Installation

Piping can be installed up the inside wall; through the wall at a slight angle and up the outside wall. The choice depends on ease of installation, visibility, and the necessity of insulating all exposed vent pipe (i.e. if the toilet is to be used consistently through a cold winter).

Piping and fittings are of standard 2" PVC thin wall tubing. Additional pipe or fittings are easily available should you need them, from a building supply dealer. If you cannot find them near your location, they are available in 30" lengths directly through us.

  1. Minimize the number of sharp angles as each reduces vent efficiency. If it is necessary to have angles in the vent pipe, it is recommended that 45 degree angles are used whenever possible. (90 degree elbows may be used as long as no horizontal vent results - pipe may be bracketed at a slight upwards angle to prevent this)
  2. Do not lead the vent pipe downward or horizontally at any point. This may lead to the vent pipe being blocked by condensate which would cause a urine smell in your bathroom.
  3. All connectors in the vent pipe should be sealed. Use silicone for the connection of the vent stack to the toilet in case the toilet has to be moved or you have to access the fan. PVC cement may be used in the rest of the stack installation if desired.
  4. All exposed vent pipe should be insulated with the foam insulation supplied with the toilet. This is especially important for winter or residential use.
Non-electric Unit (4") Piping Installation

Piping can be installed up the inside wall; through the wall at a slight angle and up the outside wall (with this configuration a 12 volt fan is necessary). The choice depends on ease of installation, visibility, and the necessity of insulating all exposed vent pipe (i.e. if the toilet is to be used consistently through a cold winter).

Piping and fittings are of standard 4" PVC thin wall tubing. Additional pipe or fittings are easily available should you need them, from a building supply dealer. If you cannot find them near your location, they are available in 30" lengths directly through us.

  1. The vent stack should be installed as near to vertical as possible.
  2. Silicone caulking should be used for the connection of the vent stack to the toilet because at some time the toilet may have to be moved or your may wish to install a 12 volt fan in the vent stack.
  3. The Sun-Mar 12 volt fan is fitted inside a 10" length of 4" vent pipe for easy installation, should it be needed. It is installed by either cutting out a section of the vent immediately above the composting unit, or by raising the vent stack off of the composting unit and inserting the fan section. The fan can be used with a solar panel and 12 volt battery, or by purchasing a 12 volt adapter from your local hardware store and simply plugging it into the wall.
  4. If a 12 volt fan is installed it should operate continuously, since otherwise it forms a partial blockage in the vent stack. To install, you can either use PVC connectors or a rubberized connector.
  5. All connectors in the vent pipe should be sealed.

Leading the Vent Through The Roof (All Units)

As shown in the diagram at the top of the page, the vent stack should end about 20" above the peak of the roof so that it is less subject to downdraft. Where the piping is taken through the roof, the roof flashing provided may be used to seal the installation or if a new roof is being installed, the roof flashing should be laid underneath the new roofing material.

DO NOT install horizontal sections of vent pipe to avoid leading the vent through the roof.

If you have a Sun-Mar Mobile unit, you may terminate the vent above the deck/roof with an appropriate vent cap, available from any marine/RV store.

The Diffuser (All Units Except Sun-Mar Mobile)

The diffuser provided with the unit is a simple device to be installed at the top of the vent stack with the larger pipe protruding above the smaller.

The diffuser design encourages updraft, and discourages wind and weather from going down the vent stack. Unlike wind turbines, diffusers are less likely to freeze up in winter, and are more effective in calm weather.

Sun-Mar Mobile units do not include a diffusor, and an appropriate vent cap must be purchased by the owner for these units.

Electrical

All electric units are supplied with a power cord and plug which connects to a standard (3) pin 110 volt outlet and powers both the fan and heating element.

It is recommended that all units be installed on a GFI (Ground Fault Interrupt) circuit to protect your unit from power surges.

12 volt fans for non-electric and AC/DC models can be installed in-line with the stack, and connected to a battery which draws from an alternate source of energy, such as a solar panel. Click here for information on the 12 volt fan and its installation.

Drains

Electric units include ½" emergency safety drains. These should be connected for residential use, or if heavy use or power outages are anticipated.

NE (Non-electric), AC/DC, Spacesaver and Sun-Mar Mobile units are all fitted with 1" drains, which should be connected to an approved drain pit, container, or other facility. Click here for more information on handling excess liquid.

Winter Use

Sun-Mar composting toilets serve as a reliable year-round facilities when prepared for continuous or periodic use during the cold winter months. If you use your cabin only once in a while in the winter, the unit may be used as a holding tank during this time.

If your Sun-Mar will be in use every weekend in the winter, or used continuously in a residence, the temperature must be kept above 55 degrees F at all times to keep the compost going. Click here for more information on winter use.

What's In The Box?

Click here to see what parts are included with your Sun-Mar.


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