RoadAbode Fall Project - Adding a Fresh Water Tank Access Port

We are always looking for ways to improve the quality of living RV life with RoadAbode. One item I always wanted was easier access to our fresh water tank. RoadAbode does not have a gravity fill spout like some RVs, so water needs to be either pumped into the fresh water tank or come from a pressurized source while boondocking (dry-camping). I've always wanted the ability to clean the inside of the fresh water tank. Currently it is a sealed system, so the only way to clean currently is to run a few capfuls of bleach thru the city water connection into the tank, and then let that slosh around as we drove down the highway. I usually would do this procedure by putting some bleach into the hose, and then connecting to the city water inlet on RoadAbode, then to a water bib (faucet) and set my water system in RoadAbode's basement to be able to fill the fresh water tank. Not hard, but I was never sure how clean the tank really was - with no visual or other inspection.

Boats that have self contained fresh water systems have watertight access ports, why not RoadAbode? I found a few RVers (who were also boat owners) that had added their own ports, so I did some reading on boating forums and planned how to do this project.

Parts List
Below are the parts I purchased on Amazon, had at RoadAbode, or purchased at our local Big Box Hardware Store:

• SeaDog Screw-Out Deck Plate - 6" 
• "Sharpie" - Indelible marker
• 6 - #6 x 1/2" Stainless Steel Screws
• Phillips head screwdriver (I used my pocket multi-tool, like always)
• Loctite Silicone Waterproof sealant - Aquarium safe
• Retractable Utility Knife
• Hand towel or rag

Prep Work
First I had to access the fresh water tank. RoadAbode's is under our queen bed in the back, so even though the under storage is hinged with hydraulic lift arms to hold it up, it was easier to get the mattress and bedding out of the way. I just pulled the whole mess forward to the living area and leaned it against the refrigerator.

Bed without mattress. Plywood not finished in any way!

I used one of our LED lanterns to provide lighting to see my work area. The under storage is split front to rear down the middle. One side holds the water tank, the other plumbing, electrical, and the water pump.  There is a protective piece of plywood - painted black - over top of the water tank which I removed and slid to the other side of the under storage.
Once the tank was accessible, I wiped it down with a clean hand towel to remove the residual dust that was sitting on top of the tank.  I opened the access port, and using the outside mounting ring as my template, I drew on the tank with the marker. I drew around the inside diameter, knowing I would need to cut a little larger to fit the mounting ring into the hole I was going to make.

Tank marked, now comes the scary part - cutting!

I selected the spot for the hole closer to one end and not the middle for a few reasons.
First, and most important, the top of the tank sloped inward to the center. When I was testing various places to put the port, it would not lay flat in the center. The best place where it laid "flush" on top of the tank was closer to the front.
Second, to access the port while camping, it would be easier near the opening of the bed. If one person holds the mattress up, the other can even work there - to visually inspect the tank, or just to add some bleach, or a few gallons of water.

Actual Work
Cutting the hole was about as difficult as I expected, maybe easier in some respects.
The blade of my utility knife was brand new, and sliced into the plastic easily. The tank material is not as heavy as I expected. I cut approximately 1/8" outside the marker line, knowing I would have to trim a little more for a nice, snug fit. First I worked around the making slits around the mark. I just pushed the knife in for each slit, and extracted. I did not want to twist the knife, which could crack or break off the thin blade point. Then I worked to connect together the slits made using a sawing, or "old-fashioned can-opener" motion. The hardest part was thinking about "I'm cutting a hole in a perfectly good tank. Hope this is not stupid!"

Here we go!

Half way done

20 minutes later, a hole appears!

I was happy to see that the water was very clear - no film on the inside edges of the tank, and smelled good to! There are tiny "ripples" of sand resting on the bottom, which next time we winterize I am hoping to clean out  - now that we have an access port!

They are hard to see, had to darken in the photo - "sand ripples"

I test fit the port mounting ring, and noted the areas that needed to be trimmed. I trimmed this way about six to eight times - test fit, trim...test fit, trim..... and so on. I prefered to cut to little, than too much. I did this until I had the mounting ring "pop" into the hole. I also made sure the port screwed in well - so that the pressure of the tank against the mounting ring was not warping the mount in a way I could not see. Everything fit nicely though.

Hole trimmings - eww - look like toenail clippings - dime for scale.

Test Fit - Now to apply the sealant

After test fitting, now came the moment of truth - sealing the port in. I used aquarium safe sealant - figured if it was safe for fish, it should be fine for us. I generously applied it to the underside of the ring (sorry, no pictures, I didn't want silicone goop on my phone) and also applied to the tank outside the hole to help with adhesion. I pressed the ring in, and then attached and started the stainless steel screws in their mounting holes. (but did not tighten all the way down just yet) I ran my finger on the inside of the hole, and could feel the sealant oozing through more in some places than others. I ran my finger around to help it even out into any crevices I felt around the rim, being very careful not to get on the threads of the port - where the access panel screws into the mounting ring.
After that first pass, I did do again after the screws were all fastened down. I tightened the screws evenly across from each other, so the port seated nicely, and some sealant was seen coming out of the outer top edge of the ring.
The sealant needs to cure for 45 minutes, so I left the port open allowed that to set while I sat with a drink and some reading. I did check the fit of the port and felt the underside of the hole for any more sealant pushing through. (no problems)

Cleanup
The hardest part of the cleanup was remaking the bed! There was sealant left, but from my previous projects, I knew the tube would harden before I got to use the little bit left. Throwing it away is still cheaper than having someone else do it! I had a few stainless screws left, and used them to hold down a piece of loose moulding in RoadAbode's rear bedroom.

New Fresh Water Tank Access Port In Place!

The total job took about 2 - 2 1/2 hours including waiting for the sealant to cure and cleanup. Glad I used the utility knife, It worked fine (though slow) and my original idea of using a drill and small coping saw would have gotten plastic dust both inside and out of the water tank. That would have been messy.
Only thing I would have changed was using #8 size screws - the #6 Screws were small, but seem to hold fine. 1/2" length seemed about right. Time I guess will tell.

Thanks for reading, hope this description of the install is helpful if you are planning to do the same job. Happy and Safe Travels, see you down the road!