Thursday, September 21, 2023


Ask Dave: Water line valves stuck. Is there any way to lubricate them?

Dear Dave,
We did not use our motorhome during the pandemic and now the drain lines are stuck. They are PEX and the shut off fittings are PVC. They are so hard to open or close that we got our grandson to get them closed so we could use our RV. Now they are so hard to open we can’t get them to move. Any suggestions of how to get them to where we can open and close them ourselves? We tried using silicone spray but that did nothing. We know that you can’t use something like WD-40 on PVC. Where they are located it is impossible to get a wrench on them so you have to have strong muscles. Thank you in advance. —Barbara, 2017 19-ft. Leprechaun motorhome

Dear Barbara,
As you indicated, most manufacturers use a plastic water drain line commonly called PEX, which is cross-linked polyethylene piping. Most use red-colored PEX for “hot” and blue for “cold.” It has become popular as it is flexible and easier to install than copper and does not have the plastic taste of the old gray or beige “mobile home” piping. Plus, it has the capability to expand and contract to 1.5 times its size so it can freeze without bursting… I have done it! But I would not recommend that because other components such as valves and fittings can freeze.

There are several different brands of PEX tubing such as Apollo sold by Home Depot, Watts at Menards, and Flair-It used in the Winnebago product. They are all very similar, but the difference, in my opinion, are the fittings they use. Winnebago uses Flair-It fittings, which are a barbed fitting with a plastic compression nut. The RV water line valves are also Flair-It and made of plastic.

Some manufacturers use a metal pinch ring at the fitting and valves that require a crimp tool.

These fittings have a barb that goes into the hose and gets clamped, and has a plastic body valve. There are also several fitting and valve manufacturers such as Midland Metal, US Brass, LaSalle Bristol, and others. My guess would be your Coachmen probably has a LaSalle Bristol, as this is a Patrick company and very popular in mid-range Class C units.

Why the RV’s water line valve is stuck

You are correct in the statement not to use WD-40, as it is not food grade and may deteriorate the plastic. What most likely happened is during storage the temperature changes resulted in an expansion and contraction of the plastic material. The valve is designed with a base tube, as you see in the photo, and a tube or plunger inside it that has a hole on one side similar to a ball valve. As you turn the handle, the hole rotates and when it aligns with the incoming pipe water flows through. It seems as though the temperature changes and expansion and retraction have created either a swollen base or plunger that has somewhat “welded” itself to the plastic.

You will need to use a food-grade lubricant that is designed for plastic such as CRC, which you can get at Amazon here.

There are other brands, as well. However, CRC has been my choice for lubrication for years as it penetrates well and lasts a long time. I would recommend spraying just under the handle as there should be a “lip” between the handle and the base component. Soak it really well and let it sit for an hour or more. Then try to move the handle. If it is still hard to turn, I would apply some heat to the valve body. Use a hair dryer as it will not heat it hot enough to cause damage, but can loosen the “weld” that might have formed. If you can get it to turn slightly, keep spraying and turning to get it to loosen.

An “old school” lubricant for those plastic valves that I used back at Winnebago—when we had the in-line drain valves that had a ring and you needed to pull the plug up to drain—was cooking oil! It was a little messy but really penetrated and lasted a long time once it worked its way into the valve body.

What RV water line valve is it?

My next question is, can you identify what valves you are having trouble with? If your grandson was able to close them, as you indicated, they are most likely fresh water drain valves and probably low point valves. You can replace the valves, or install a second valve downstream.

If you can supply a photo, we should be able to provide more info on how to replace or add another water line valve.

 You might also enjoy this

How to lubricate sticky RV dump valves

By Doug Swarts
We’re asked often about the proper method to lubricate a sticky RV dump valve. The RVers are usually referring to the black 3-inch gate valve on their black holding tank. In some cases the 1.5-inch gray valve gets sticky over time, especially if the RVer is not using his RV full time. The contents inside the valve dry out, causing the valve to stick. Continue reading.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


  1. I recently bought a brand new $100K+ triple slide truck camper that used the metal pinch rings throughout to connect the water line fittings. Despite the mfg’s claim that they ran water tests for 2 days before delivering to the dealer, & the dealer claiming they also ran 2 days of water tests, I experienced 6 separate water leaks in the first month of use. Those metal crimp rings are useless. I fixed the leaks with Flair-it fittings that I’ve used for years on my other rvs.

    • I’m surprised with your experience with crimp rings. I have modified my plumbing a bit using them and have not had a single leak. Maybe the manufacturer was a bit careless.

  2. Got an update from Barbara;

    Just to update you …the spray worked perfect on the valves…thank you so much for solving our problem…God Bless Barbara

  3. Speaking of PEX, I don’t remember the name brand but a representative of the company was at the school system where I worked several years ago demonstrating the PEX tubing. He had a section of 3/4” tubing filled with water frozen solid that was about 2 1/2” in diameter. He thawed it with a heat gun and it still didn’t leak, very impressive demonstration as to the strength of PEX.

  4. This is not only an RV problem. PVC, CPVC and Pex plumbing have the same problems in the Plumbing problem. I suggest the same solutions. From a Plumber.


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