Connecting 2 LP Tanks on an Early Discovery

The purpose of this article is to explain how to connect the Generator LP tank and the Coach LP tank on early model Discovery motorcoaches. Through the 1998 model year, the D only came with an LP generator. A diesel generator was offered as an option in 1999. Starting with the 2000 model year, the diesel generator became standard. This article is NOT applicable to those of you that have a diesel genset.

The main advantage of connecting the two LP tanks is that your COACH has access to the 24 gal coach LP tank and the 40 gal generator LP tank (both are water capacities). Note that this will not extend the available LP for your generator, mainly because the generator uses liquid LP and the coach uses vapor, and it is a very slow process for the propane to transfer to the generator LP tank. However, this modification is very beneficial as you can use your 40 gal generator LP tank to provide LP to your coach appliances. This allows me the freedom to wait until I find a good price on propane as I rarely use the generator extensively.

There are several ways to connect the LP tanks. The easiest way is to use the Marshall Brass Extend-A-Stay as you will not have to drain either LP tank. Here is a list of parts that I needed for my installation with my existing Extend-A-Stay:
54" of high-pressure LP gas hose (at least 300 psi), cut to approx 30" and 24" lengths, with four ends 2 1/4" x CLS Galvanized steel pipe nipples 1 threaded 1/4 inch ball valve 2 1/4" x 1.5" brass pipe nipples Teflon Pipe tape For all pictures below, click on the thumbnail for a larger view.

Figure 1 shows my LP bay in my 98 36T prior to the conversion, but with the Marshall Brass Extend-A-Stay installed.

Figure 2 shows the completed conversion.

Figure 3 shows the original Generator LP tank bleeder valve.

Figure 4 show the T added at the Generator LP tank bleeder valve

Installation Procedure (with the Extend-A-Stay):
If you are not confident in what you are doing, have a professional install it for you!

Turn off the generator LP tank. (You will have to crawl under the coach to do this).

1. Turn off the coach LP tank.
2. Open the bleeder valve for the Generator LP tank (located in the LP Bay). A small amount of LP gas will escape from the hose (Reminder - make sure the LP is shut off at the generator tank!). Disconnect the LP hose fitting that goes to the bleeder valve for the Generator Tank and insert a T between the existing hose and bleeder valve.
3. Connect the hose to this T and the other end of the hose to one end of the ball valve.
4. Connect the other hose to the vacant end of the ball valve. At the Marshall Brass Extend-A-Stay, remove the ball valve that connects to an "external tank port" and replace it with a T. The other end of the hose to the ball joint will connect to the T and make sure you cap off the other end of the T (which is where you will connect your external LP tank (if you will ever need one again).
5. Make sure that you use your teflon tape on all the connections.
6. Secure the ball valve and ensure that the hoses are not rubbing on anything.
7. Check the system for leaks.

Total cost for parts was approx $40.

Installation Procedure without an Extend-A-Stay:
If you are not using an Extend-A-Stay, you will have to make sure that your coach LP tank is empty as you will be removing the bleeder valve and installing a T as you did at the generator bleeder valve. The hose will connect at this point instead of the Extend-A-Stay.

Operation:
Use the ball valve and the ON/OFF valve on the coach LP tank to determine which LP tank you are using to provide LP to your coach. If you leave the ball valve open and also open the valve to your coach LP tank, the two LP tanks will tend to equalize. I almost never do this. I always use my coach LP tank first and then switch over to my generator LP tank when my coach tank is near empty. When filling either tank, close the ball valve.

A WORD OF CAUTION

The legality of this modification is unknown, so do it at your own risk.