How best to make access door for holding tank?

[Kevin Warnock]

What would be the best way to make an access door for a plastic waste tank? I want to put a float switch on the inside bottom so I need to be able to get inside. I was thinking about a 4" ABS drain clean out plug, but I can't find a cheap way to get 4" bulkhead threads on the tank. The plug is $2 but the bulkhead fitting was over $100. This access will be on the top of the tank, so it doesn't have to be liquid tight. Thanks.

[Jeremy]

An inspection hatch cover from a boat's buoyancy tanks would do the job - see below for an example:



Jeremy

[scanzel]

A holding tank should be sealed against leakage especially a waste tank. Stuff will slosh around if you were not able to dump right away while traveling. Very messy trying to clean up latter. Go to www.Plastic-Mart.com and look at inspection covers. These are made to be added latter, cut the correct size hole and bolt in place, they have a screw in cover the prevent leakage.

[jackhartjr]

Mayby I just got up and the cobwebs still have not cleared...however...why are you putting a float switch in the waste tank?
Thanks
Jack

[Len Silva]

Several possibilities using 3" RV hub fittings with threaded or bayonet caps. http://www.bigdiscountrv.com/plumbing/waste-valves.htm

[Kevin Warnock]

This looks good:

http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/102899/377%20710/0/inspection%20hatch/Primary%20Search/mode%20matchallpartial/0/0?N=377%20710&Ne=0&Ntt=inspection%20hatch&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=0&Ns=0&keyword=inspection%20hatch&isLTokenURL=true&storeNum=5000&subdeptNum=24&classNum=460

as it's a clear plastic, water tight inspection hatch for marine use.

Thanks for the suggestion to use an inspection hatch for a boat. I didn't know about these, and they seem more suited than a large plumbing fixture hub and plug.

The reason I want to put a float switch in a gray water tank is I will have the fresh water and grey water tanks under the bed, where it's already heated and cooled. I will put one 40 gallon tank in the bay of my RTS and have the drains all first drain there by gravity. Then, when it gets full, the switch will activate and a macerator pump will pump its contents to the two ganged 40 gallon gray water tanks under the bed. The pump will only cycle once every 40 gallons, so I think I can live with that little extra noise. Does anyone know if I violate some kind of code by this proposed setup?

That leads to a new question... How to keep the single bay mounted 40 gallon tank from freezing? I was thinking about making a box for it in the bay under the bed and lining this fitted box with rigid foam insulation, and then making that box part of the living area of the bus by cutting an air hole in the floor under the bed, so that heated air from the bus would naturally circulate around the bay mounted tank. I would caulk the corners of the bay tank box so it would be air tight, so this space would still be "inside" space of the bus. Yes, the bed is directly over a bay, not in the back by the engine. I live in California so don't have to normally deal with freezing temperatures, but I want to make the bus able to go to Tahoe in the winter for example. I am trying to keep the bays relatively empty so I have room for bikes and stuff.

Thanks

[CindyandJohn]

FWIW - I put one of these on each of my tanks... so far no issues. Water tight... A very easy way to access the inside of the storage tanks. I needed access to install my fittings and such. Main purpose of these is to clean the tanks.

http://aquasaverbypjbcompany.com/

John

[NewbeeMC9]

For freeze protection, google "waterbed heaters"



For level checking on a translucent plastic,  At a viewable side, cover the side with a piece of ply wood or paint the side etc, leaving a vertical slot and put a light on the tank so it shines behind the board.  You will be able to see the level with no penetrations of the tank.

mainly just need something that lights the inside of the tank but does not shine directly in your eyes.  Same principle as an aquarium cover light.

if you put the light back far enough, you want need a slot on the side.  I see this as an advantage of plastic tanks.

You can try it by just putting a flashlight down on the top of the tank.



let us know what you come up with.