Thursday, June 8, 2023


An easy fix for a shower that won’t drain

If you’re showering in your RV and you’re standing in a couple of inches of water, or if the water just isn’t draining as quickly as it should, you have an issue that needs to be resolved.

So why isn’t your RV shower draining? Let’s take a look at one of the most common issues that lead to a clogged RV shower and/or slow draining. There are a number of other reasons that could cause the shower to clog or backup. For example, it could be something as simple as that your gray water tank is full. It could also be that your tank sensors are reading incorrectly, or it could just be something else…

For most of us, we are all somewhat familiar with a P-trap being under the galley or bathroom sinks. But did you know that most RV showers don’t use a standard P-trap anymore?

Standard P-trap

For the most part, the RV industry has been using a device called a HepvO valve. Unlike a typical P-trap, the HepvO requires no water to seal off nasty waste tank odors. Since the valve is waterless, there is zero chance of freeze damage or water that can evaporate from a P-trap letting tank odors in the rig.

HepvO kits allow different space-saving connections.
View underneath most RV showers.

HepvO maintenance


The HepvO sanitary waste valve does not require routine or seasonal maintenance. However, if you need to blow out your drainage lines, make sure not to exceed 80-100 psi.

HepvO is highly resistant to standard caustic-based drain cleaners and can withstand acid-based cleaners with concentrations up to 10%. If you need to flush with higher concentrations of acid-based cleaners, the valve must be removed before the operation.

If you plan to use mechanical drain cleaning devices, it is important to first remove the HepvO from the waste system. This allows for easy access to service downstream pipework. After any maintenance procedure, it is recommended to rinse the HepvO valve with clean water.


To clear a pipe blockage downstream of HepvO, it is advisable to temporarily remove the HepvO valve before using a pipe rodding technique. Rodding the pipeline with the HepvO valve in place may result in potential damage to the internal components of the valve.

What does a blockage in a HepvO P-trap look like?

I would recommend that you add this inspection and cleaning to your regular RV maintenance schedule at least once a year depending on use. You should be able to access the HepvO P-trap by removing a panel underneath the shower, or you will need to see if it is located in a compartment underneath the shower area.

Remove the HepvO P-trap for cleaning.
This is the drain end of the HepvO, as you can see the hair trapped inside it.
This is the inlet side of the HepvO P-trap clogged.
This cut-a-away shows you an example of how it works.
Cleaned the inlet side of the HepvO P-trap.
Cleaned the inside of the HepvO outlet side.

If you’re battling odors in the bathroom or a slow or clogged drain, we would recommend that you check your HepvO P-trap. Please see the manufacturer’s website for installation and additional resources if needed.

What is the life expectancy of a HepvO valve?

Installed correctly, it can be expected to have a life expectancy at least equivalent to current water-sealed traps. In addition, HepvO is guaranteed against defects in materials or manufacturing for a period of 3 years.

Here is the product link if you need a replacement or simply just do not want to clean it.

More from Dustin

Read more of Dustin’s articles here.


Dustin Simpson
Dustin Simpson
I have worn many hats in the RV industry through the years. From an RV Technician, Warranty Administrator, Parts Administrator, Parts Manager, Service Manager and now Business Owner. I have even been deemed an RV Expert by the California court system, working on behalf of the customers, dealers, and manufacturers. My repair facility has been servicing customers at the same location since 2003. What sets us apart from the dealerships is we are here to fix and maintain what you have, and not sell you a new one. Whether you own a million-dollar unit or an entry level, my message to you will be the same, it needs to be maintained.


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Jesse Crouse
1 month ago

From a Plumbing service co. Never install anything you can’t get to for service. You will be sorry!

Jesse Crouse
1 month ago

Most shower traps are in hidden areas or with no access to them.

1 month ago

This is some serious good information that I wasn’t aware of. Thanks Dustin and Will B

Neal Davis
1 month ago

Thank you, Dustin! I’ll ask Newmar what is beneath our shower drain. It is a wide slit in the floor, so rather attractive, but also may entail a difficult method of unclogging it.

Tommy Molnar
1 month ago

If this valve is under the shower, how in the world do I get access to it to remove it?

Dustin Leigh Simpson
1 month ago
Reply to  Tommy Molnar

You should have an access panel underneath the shower or you may have to go through the compartment area to gain access to it.

Tommy Molnar
1 month ago

I DO have an opening under the shower but there’s no way to simply do ANYTHING under there. Luckily, our shower is working just fine. But as they say, everything works fine right up until it doesn’t. Ha.

Tom H.
1 month ago

I’ve found that a little baking soda and white vinegar in the drain cleans it right up.

Tom H.
1 month ago

I’d never heard of a HEPvO valve until we were installing a washer/dryer combo in our 5er. Upon running the washer for the first time the drain immediately backed up. Water started pooling in the bedroom. Not good! After shutting down the washer and cleaning up the water I started an investigation into why this happened. I found the HEPvO valve in the drain line and thought “what in the world is this”. After some research I discovered what it was and how it works. I also discovered that it was clogged with pipe shavings. Apparently it was not cleaned out after installation by the factory. Anyway, I learned 2 things that day. What is a HEPvO valve and test all of your RV drains during the PDI.

1 month ago
Reply to  Tom H.

? PDI = Pre Delivery Inspection ?

Will B.
1 month ago

Here’s a hint — DO NOT PLUNGE this. Ask me how I know.

1 month ago
Reply to  Will B.

OK, I’ll bite. How do you know not to plunge this valve?

1 month ago
Reply to  T G

Because the valve has a silicone duck bill valve internal and if you use a plunger you will destroy the duck bill and you don’t want to be around your RV as the gray tank gasses will come into your shower.

Last edited 1 month ago by Engineer

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