How to Virtually Eliminate Holding Tank Odors in Your RV

It’s probably no secret to you that your RV holding tanks have the potential to create a source of undesirable odor within your coach. Even with proper use of deodorizing chemicals and rinsing of tanks, odor can still be a troublesome problem. Here's how to virtually eliminate odors from your tanks, using a fan-type device called the Lil' Stanker, providing a stink-free RVing experience.

Instructions

Difficulty: Moderate

Things You’ll Need:

• Lil' Stanker MK-IV stainless-steel holding tank deodorizer fan
• RTV Silicone sealant or Dicor rubber roof sealant
• Drill and/or Phillips head screwdriver

1. Black tank vent cap Locate the correct holding tank vent cap. On the roof of your RV, you may have more than one holding tank vent pipe cap. If you do, pick one pipe and follow it down to the tank it's attached to. Ensure that the vent pipe you select goes to the BLACK tank. Remove the cap by giving it a gentle tug. It should just pop off.
   
   Sometimes, both the gray and black water tanks will vent through a "Y" fitting into a single vent pipe. If this is the case, you will only have one vent cap on the roof.
2. Vent cap removed The Lil' Stanker fan will mount on top of the vent pipe. The fan requires electrical power to operate so we have to determine where to route the wires from the fan to the power switch that operates it. You can either choose to route the fan wiring along side or down the vent pipe. If you choose to go down the pipe, you will have to drill a small hole in the vent pipe inside the RV to pull the wires through.
3. Vent pipe max height Next, confirm that the tip of the vent pipe is no more than 1-7/8 inches above the roof's surface. (Any greater height will interfere with the fan's mounting). If necessary, shorten the vent pipe with a hacksaw, and remove any sealing boot or cover mounting base pieces that would otherwise interfere with the fan’s fit.
   
   Temporarily set the fan over the vent pipe, until its mounting base rests on the roof. Confirm that nothing prevents the fan from resting solidly on the roof's surface.
4. Sealing air gaps Use sealant/adhesive to fill-in any air gaps where the vent pipe passes though the roof. (If the fan wires are to be routed along the outside
   of pipe, leave a small gap in the sealant where the wires will pass through). The goal is to minimize air leakage between the outside of the pipe and the roof hole it passes through.
   
   If the fan wires are to be routed through a hole in the roof, drill this 1/8" hole now. Pick a hole location that will be sheltered underneath the fan after final attachment.
5. Fan wires going down the vent pipe Route the fan's DC power wires either (1) down the outside of the vent pipe, (2) down the inside of the vent pipe, (3) through the previously-drilled 1/8" roof hole, or (4) under the bottom edge of the
   fan. If the fan is to be attached with the 4 mounting screws (included in kit), use the fan to mark the locations of the mounting screws on the roof, and drill 1/8" holes approximately 1/4" deep into the roof at these points.
6. Securing the fan Next, thoroughly clean the roof's surface where the fan will be mounted, and apply a bead of sealant/adhesive all the way around the bottom of the fan's mounting base (and inside the 1/8" roof wire-routing hole, if used). Set the fan in place, securing it with the mounting screws (if used). Apply sealant to the tops of the screws (if used).
7. Snaring wires from vent pipe If the fan's DC power wires are not being routed down the inside of the vent pipe, go on to STEP 9. Otherwise, proceed as follows: Locate a convenient point somewhere along the vent pipe, near a source of DC power. Drill a 1/4" hole in the pipe at this point.
   
   Insert the hooked end of the Snare Wire (included in the fan kit) into this new hole, and snare the power wires with it. Gently pull the power wires out though the hole.
8. Securing power wires to vent pipe At the point where they exit the hole in the vent pipe, bend the power wires flush with the pipe's surface. (Make sure that most of the slack wire has been pulled out of the hole, in order to prevent any chance of accidental wire contact with the fan blades). Secure the wire in place several inches below the hole with the Plastic Wire Tie (included in the kit). Tightly apply the Sealant Patch (included in the kit) around the hole and wires until an air-tight seal is formed.
9. Fan switch connections Select a convenient, non-metallic mounting surface for the fan shutoff switch inside a closet, cabinet or other compartment, near the fan's power wires. Cut the fan’s wires next to this mounting location. Strip approx. 1/4" of insulation off both cut ends of both wires, twisting any frayed wire strands back together again. Insert these bare wire ends into the holes in the sides of the green terminal block on the switch as shown below, and tighten each of the 3 screws on the top of the terminal block with a small screwdriver. Note that both WHITE wires go to the same CENTER hole in the terminal block.
10. Fan switch mounting Next, mount the switch in the switch enclosure (or your own panel), securing it with one switch nut. Use the two mounting screws to attach the enclosure (if used) to a flat mounting surface, after routing all wires out the small slot on the side.
11. Final installation Finally, strip the ends of the power wires and connect them to a FUSED source of 12 volt DC electrical power (GREEN fan power wire to POSITIVE, and WHITE fan wire to NEGATIVE). IMPORTANT: MAKE CONNECTIONS EXACTLY AS SHOWN. FAN WILL NOT WORK IF WIRING OR BATTERY CONNECTIONS ARE INCORRECT.
    
    The recommended fuse size is 0.25 amps (for 1 fan) or 0.5 amps (for 2 fans). This completes the installation.

Tips & Warnings

• To run the fan, simply flip the switch to either the LOW or HIGH positions (LOW is recommended for most conditions). The green indicator light on the switch will illuminate whenever the fan is running. The fan may be left on whenever the RV is occupied, but should be shut off before putting the RV into long-term storage.
• No one solution will prevent holding tank odors from permeating your RV. Use this how-to along with proper holding tank cleaning, odor control chemicals, purpose made RV toilet paper, and plenty of water with each flush.
• Although black water tanks are usually the worst odor offenders, many RVers will further benefit from the installation of fans on both holding tanks. This eliminates the gray water tank as a source of odors previously masked by the black water tank.
• The manufacturer of this product also has an alternative fan that installs inline with the vent pipe, rather than on on top of it. For some installs, this might be an easier solution. See the Resources link below for the product web site.