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RV Holding Tank Shapes - Could Yours Cause Waste Build Up?

March 21, 2019

What is the shape of my rv boat camper trailer fifth wheel black gray water holding tanks and how does it lead to clogs pyramid plugs poop pyramids blockages blocks backups back-ups leaving your black tank valve open

Believe it or not, the actual shape of your RV holding tank can be a big reason why you struggle with waste tank clogs. The construction and design of your holding tank, as well as how it is mounted to your RV, have a surprisingly large impact on how susceptible you are to getting pyramid plugs and clogs in your tanks. Understanding the shape of your holding tank can help you avoid these messy mistakes.

In this article we will go over some of the biggest structural problems with your RV's holding tanks, as well as some treatment techniques and advice to keep your RV tank clog and hassle free.

To get started, let's go over some holding tank shape problems that you should be aware of.

Holding Tank Shape

Why is your holding tank shape important? It important because certain shapes are more prone to clog and harder to clean than others!

Quick fact: nearly all RV holding tanks use gravity to drain - there is nothing pushing the water our of your tank, it is just naturally flowing out - so, the geometry of a holding tank can cause issues if water isn't easily able to flow out of the tank.

For example, one issue we help customers solve all-too-frequently is "pyramid plugs" (aka poop pyramids). These are a direct result of two things:

  1. Leaving your black tank valve open
  2. The flat bottom of your tank

When you leave your black valve open, the water and urine are able to flow out of the tank with relative ease, while the paper and poop waste fall to the bottom of the flat tank surface and, over time, can become a pyramid of poop and paper.

You can prevent this by following The Unique Method.

Another frequent problem we hear about is old, dried-up waste collecting in the tanks - even when you are treating your tank with a high-quality waste digester and flushing your tanks.

The reason for this is that most holding tanks are not installed perfectly level, nor do most RVs get parked perfectly level, so it's only a matter of time before waste starts to build up in the nooks and crannies (the corners) because it cannot flow out with gravity.

This is why it's so important that you follow The Unique Method and flush your tank very thoroughly on a regular basis. Just flushing your tank for a couple minutes until "the water comes out clear" doesn't mean that you are cleaning up that crusty, old, waste that has hardened in the corners of your RV holding tank. To rinse out this waste, it often takes flushing for a significantly longer time - 20 to 30 minutes - before you get a second whoosh of black tank waste leaving your holding tank. This is because gravity alone cannot empty the liquid and solid waste from un-level tanks. Over time there is bound to be residue.

Build-up can be even worse if the holding tank doesn't drain out of the bottom of the tank. On many tanks the drain is mounted on the side of the tank. Because of this, there will often be a lip that retains a layer of waste on your tank's floor, making it hard to drain all of the waste. This is another reason why you should flush your tanks very thoroughly, regularly.

Now that we have talked about your RV holding tank, let's talk a bit about plumbing. 

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Holding Tank Plumbing

The plumbing in many RV bathrooms is configured with the toilet directly above the holding tank, so it is a straight drop to the tank. There are also many RV's where the toilet is NOT directly above the tank, so long and winding pipes may be required to deliver your toilet waste to the holding tank. As you can imagine, it is not hard to get paper and feces clogged in these lines BEFORE they even reach the tank!

An RV toilet that drops straight into the holding tank is far less prone to getting back-ups in the line, but it can still happen. 

Avoiding back-ups in the plumbing before the holding tank is simple: Water!

  1. Always fill your toilet bowl with water BEFORE and AFTER you go to the bathroom
  2. Hold your toilet flush peddle down for 10 seconds each time you flush

If you don't do these two things, toilet paper and waste can get stuck in your pipes.

Also, using too much toilet paper can lead to clogs and back-ups in the line, so be careful to not use too much.

Besides clogs, having extra plumbing between your RV toilet and your holding tank also means you have more opportunities for for leaks in some form or another - especially if your plumbing isn't well insulated and temperatures get below freezing.

We recommend doing an audit on your waste water systems periodically to make sure everything is in good shape.

Problems can occur whether your RV is brand new or used and each manufacturer does things a little differently, so it is up to you to follow good holding tank habits to avoid costly and disgusting repairs. Remember, we are always here to help you along the way!

Our Recommendations  

There are a lot of differences from one RV to another, with their waste water systems, but there are a few key things you can do to help keep some of the possible issues at bay regardless of the brand or model of RV you have:

    1. Flush your tank for longer periods - We suggest 20-30 minutes of running water to make sure all of the nooks and crannies in your holding tank are clean.
    2. Use a high-quality waste digesting RV toilet chemical like RV Digest-It. By using a waste digesting treatment, you help to break down solid waste in your tank and prevent build-up and clogs.
    3. Fill your RV toilet before and after each use - this will help to keep plumbing from getting backed up or compacted. 

The reality of holding tank issues is that they are all unique. Containing waste while on the move is a messy subject and can cause huge headaches for RVers. Be diligent with how you treat your water systems and you will help mitigate these potential problems.

Remember that we are here as a resource for you. If you are ever dealing with a waste issue in your RV, we are here to help, please contact us! You can reach our support team at support@uniquemm.com. They will work to get you back on the road!


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