Mod #57: Holding Tank Odor Controller

Mod #57: Holding Tank Odor Controller

Submitted on: 10/02/08

     Category: plumbing
Mod Rating: 12345

(60 ratings)

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Mod Description:

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.

Mod Difficulty: 

In this mod, we’re going to walk through the steps required to install the Lil’ Stanker fan. When you buy this fan, it comes with a installation kit and containing all necessary parts, including a power switch to turn the fan on and off. Each step in this mod has a corresponding image above and the images are in the respective order of the steps below.

First, 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.

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.

Now 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.

The next step is to 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.

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).

If the fan’s DC power wires are not being routed down the inside of the vent pipe, skip the next step. 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.

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.

Next, 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 as shown in the image above, 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.

Now 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.

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.

TipTo 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.

TipAlthough 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

ModMyRV recommends these parts for this mod:

Holding Tank Odor Control Fans
Lil’ Stanker RV Holding Tank Odor Control Fan

General Reference
How to Empty Your RV Holding Tanks
How to Manage Water Usage in Your RV

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10 Comments For This Mod

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  1. RV Camping World

    I do sleep a better knowing the Lil Stanker is working !!

  2. Matthew Scott

    I would imagine this works to some extent, but there is a problem with the design. There is ONE vent pipe. If you extract air continuously from that pipe, where is the fresh air going to enter? There should be an inner and outer pipe. You could draw from the inner pipe and allow fresh air to enter through the outer pipe. That way you would have a an unimpeded flow and continuous circulation.
    On the other hand, if you only turn it on when the toilet is in use, the reduced pressure in the tank would prevent foul tank air from entering the RV interior when the toilet is flushed. I think a bit more thought needs to go into this product.

  3. Denise in Ark

    Installing a rinser on our tank and using baking soda and dish soap with a few gals of fresh water in the clean tank has been all we need to control odors in our tank. Thank goodness.

  4. rklingborg

    After fixing my system so I can use it, and a week boondocking with my son I found out I needed something besides tabs to help with the smell, I was cheap and used a small computer fan that fit in the cover of the vent and used a LED switch to run it no more smell when the thundermug flushed.

  5. ModMyRV

    Nice rklingborg! Do you have a picture of how you mounted the fan to the vent cover?

  6. rklingborg

    Sorrry no it was a perfict fit to the inside of the vent cover

  7. Galileon

    I did this install 4 weeks ago. I figured the seals in the john must be leaking the foul odors into the camper. This has worked out great as a short term solution, I’ll wait for cooler weather to re-seal it properly! But, the Lil’ Stanker will still come in handy by keeping the odors out when flushing.

  8. AustinMike

    Glad I found this. My switch will be actuated by the flush pedal.

  9. nosticks

    I installed this mod and have not used chemicals since. It runs continuously on low when we are gone and on high when we are there. We have been stationary for 11 months. One of the best mods I did.

  10. James

    This “roof top” product is no longer available. However…. One can use ABS piping, 12 Volt wiring, inline fuse and 12 Volt 35+ CFM computer fan, I “clone” the above product design. For my RV/TT, this “35+ CFM FAN to suck the bad air out of the black tank” works great. Before using the toilet, the person simply turns the fan on, does their business, opens the toilet seat trap (with fan, the bad air is now sucked down - into the tank) and the bad air is also pushed out the roof’s vent pipe. After washing hands, the person then turns the manual switch to off. Very simple and yes, it does work. And best of all, NO more expensive chemicals to cover up the bad smell’s either.

    For the folks who think this product doesn’t work, suggest installing / trying it out for yourself. From 1st hand experience of using this product (or clone it using ABS pipe with 12V computer fan), it does work. IMO, this vent fan should be factory on all RVs/TTs. Especially since RV/TT toilets don’t use a gooseneck piping system - to keep the bad smells within the tank (or up the vent pipe).

2 Trackbacks For This Post

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    [...] time to do some maintenance and while I was up there to implement another upgrade I found on the ModMyRV WEB site I mentioned in an earlier post. The instructions on ModMyRv are better than I can [...]

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