Questions on a water tank deck plate install - Fiberglass RV

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Old 06-17-2014, 08:23 PM   #1
Trailer: Scamp 13 ft
Eastern Ontario
Posts: 94
Questions on a water tank deck plate install

I want to put a 6" deck plate on my 2010 Scamp's water tank. What I want to know is, what sealant would you use between the tank and the plate? I plan to screw through the tank and use washers and lock nuts (all stainless steel). Does the tank need to be reinforced around the hole?

We have not used the water system in the trailer (other than city water). It needs a real good cleaning before it is useable. We plan to use it this winter when we go to Arizona.

Any help would be appreciated.

Sandy C

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Old 06-18-2014, 06:42 AM   #2
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Name: Steve
Trailer: Scamp 19
Posts: 170
I am doing the same job as soon as I get home from our current trip. I'm going to use 3M 5200 as it is a very goog marine sealant/adhesive. Also it won't do any damage to either the tank plactic or the plate ring plactic. I'm also going to use pan head machine screws/bolts with washers as the plate that I have recommends these over counter sunk fasteners. The plate I have has counter sunk hole, but probably the manufacture has found that people over tighten the fastenings and split the holes in the ring. I will also use washers on the inside of the tank before putting on the nuts. I will also use 316 Stainless Steel fasteners if I can find them as they will have the best resistance to rust.

May see you in AZ. as we enjoy living there when not on the road. I have meet many wonderful people from a number of different places passing through Prescott.

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Old 06-18-2014, 07:07 AM   #3
Name: Kenny
Trailer: 16' Standard
Posts: 74
Deck Plate Access

I too am considering an access to the water tank. I was thinking of a 4" hole for three reasons, 1) the hole would be large enough to reach in for cleaning 2) hole saws are cheaper the smaller it is and 3) maintaining the integrity of the tank.
I think I would like to use one that has a clear plastic screw in plate with O ring. It costs a little more. Beckson Marine 4" Clear center screw out deck plate DP 40-W-c on Amazon.
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Old 06-18-2014, 07:08 AM   #4
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Name: Bob
Trailer: 1973 Hunter Compact II
Posts: 7,914
It sounds like you are inserting screws up through the tank wall from the inside. That being the case why not just get a large "O ring you can stretch around the 6 screws and tighten down against that..... That way you don't have to deal with problems if you want to remove it in the future.
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Old 06-18-2014, 07:13 PM   #5
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Name: Jared
Trailer: 1984 19' scamp
Posts: 1,610
They don't have a good spot for an o-ring. I attached mine with 3m 5200 and 316 stainless screws, with washers and lock nuts inside. I put a little 5200 on the washers and lock nuts, also.
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Old 06-18-2014, 07:17 PM   #6
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Name: Jared
Trailer: 1984 19' scamp
Posts: 1,610
I used 4", but I see no reason why 6" would hurt the integrity of the tank. 4" gives me enough clearance to get to all corners of my 20 gallon tanks.

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Old 06-18-2014, 09:56 PM   #7
Trailer: Scamp 13 ft
Eastern Ontario
Posts: 94
Thanks for the replies and any more are welcome. I will be tackling this soon.

Sandy C
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Old 06-19-2014, 07:11 AM   #8
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Name: Robert
Trailer: Airstream 23D International Serenity
Posts: 100
To ensure structural integrity of the tank top, I made a "mounting flange" somewhat larger than the deck plate I used (6-inch for easy access). There is an inside-the-tank flange (that I made in two half-circle pieces to fit through the hole) and an outside-the-tank piece. They are held together - "sandwiching" the tank top - using 1/4" X 20 stainless bolts with stainless "Nylock" nuts. The actual deck plate is bolted through the entire "assembly." I made my mounting flange pieces from 1/2" polyethylene (a cutting board from Ace Mart!).

The only "sealant" used was butyl tape... hardly any "sealants in a tube" will stick to the tank material.

Overkill? Perhaps, but it is good to have easy access to the inside of the tank and the whole thing is super-sturdy!

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Old 06-19-2014, 07:45 AM   #9
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Name: David
Trailer: Escape 5.0TA
Posts: 194
8" Beckson Deck Plate

I installed an 8" Beckson deck plate in my Scamp tank for easy access and used 5200 as well. I don't think the tank's strength has been compromised much if at all. Got it from Amazon. Has a clear lid, though other colors are available and slightly less expensive.

Beckson Deck Plate Installation Instructions

4" , 6" and 8" Deck Plate Installation Instructions
1. Remove deck plate center, invert, and use as a template to scribe cut line.
Go to Step 2
5" Deck Plate Installation Instructions
1. Remove deck plate center. Using the deck plate outer ring as the template and scribe line around the inside of the ring.
2. Drill 3/8" (9.2mm) starter hole adjacent to inside scribed line. Cut 1/8" (3.2mm) outside of the line (larger) with a reciprocal saw.
3. When using self-tapping screws on a deck of sufficient thickness, mount deck plate and drill screw holes partially into the deck with 1/8" (3.2mm) drill bit.. When thru- bolting, drill all the way through the deck.
Deck construction (Solid Fiberglass, or Foam or Wood core)
4. For solid fiberglass decks proceed to step 5. On a foam or balsa core deck dig out 1/8" (3.2mm) of core bordering the primary hole and around the screw holes. Fill with two-part epoxy filler and let cure. Re-drill screw holes.
5. Replace center into the deck plate ring and apply a 3/8" (9.2mm) bead of silicone caulk on the edge of the spigot (flange) and under side of ring.
Beckson recommends using only silicone sealants for ABS deck plate installations and is not liable for product damage caused by other sealants.
See Easy Clean-Up below.
Note: For installation of polypropylene deck plates, please consult your local marine dealer or caulk manufacturer for best results. Silicone will not adhere to polypropylene.
6. Fasten deck plate to deck with #8 pan head screws or thru-bolts, maintaining a minimum of 1/16" (1.6mm) of caulk as a gasket and keeping the plate flat. If on a curved surface, fill gaps completely with caulk, without bending the trim ring. Thin ring deck plates may be mounted without fasteners. If adhesion is questionable, drill and counter bore thin ring for #8 fasteners.
Do not use countersunk or oval head screws. Damage will result.
7. Note: For Easy Clean-Up when installing ABS deck plates with silicone sealant: dry mount the deck plate, and apply liquid soap to a damp sponge. Carefully wipe all areas where you do not want silicone to stick. Remove and install with a generous amount of silicone sealant. Do not squeeze out caulk beyond the edge of the ring. Carefully remove excess with a single edged razor blade or "Exacto" knife once cured.
Do not scrape the deck or the deck plate with the razor blade. If necessary, remove excess caulk with isopropyl alcohol and a soft cloth.
If necessary - lubricate deck plate thread with Teflon grease or Vaseline.
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Old 06-19-2014, 07:58 AM   #10
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Name: Tim
Trailer: '88 Scamp 16, layout 4
North Florida
Posts: 1,394
Originally Posted by Stretcher View Post
I installed an 8" Beckson deck plate in my Scamp tank for easy access.
+1, bigger and easier access is mucho bettero. Should not be any more time or trouble to install an 8" than a 4" or 6".

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