Plumbing for DC39 holding tank

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Plumbing for DC39 holding tank

Postby Spinnakermna » Thu Mar 19, 2020 9:09 am

Looking for help. I’ve looked through posts but need more info. My new to me 39DC was built without a holding tank and direct discharge. Can anyone share pictures of their installation? I understand that holding tank should be installed in area below lower helm however I’ll need to move hot water heater and some other hardware. Should pump out fitting be a siphon tube or from bottom of tank, inlet fittings at end or in side in line with incoming flow. Slope of lines from toilets and how attached in engine compartment. Have you switched to pvc instead of hose? How about vented loop? Ideally I would like option of Purasan anyone have one installed? Boat is located near Nashville and I would like to see one that has the plumbing already installed if some one would be kind enough to let me come by and have a look. Really would like to leave the dock but I won’t use the heads.
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Re: Plumbing for DC39 holding tank

Postby Fastjeff » Thu Mar 19, 2020 11:30 am

Did that years ago on my 32 footer and it was the BEST thing I did to it! That tiny tank in the stock head is a joke!

You want to jamb in there the BIGGEST tank that will fit!

You need to plumb the pump out line to the bottom of the tank. The vent line goes to the top.

Make sure the bled hose (off the top of the tank) is at least 3/4 inch size to prevent plugging. (Why? Square tanks can't sustain any pressure or they rupture. Yeauck!)

The plumbing job can be a real challenge if you haven't mess with it, so ask someone who has, or hire someone if you're not up to it.

I used white PVC piping where possible, and stink resistant hose (the white kind) otherwise. Avoid tight, 90 degree bends where possible and keep the hose run turns gentle (to prevent line plugging. Another yeauck if it happens.) Double clamp every connection with stainless only clamps.

Good luck!


PS: One of those combusting toilets is the best set up of all. A bit pricy but great.
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Re: Plumbing for DC39 holding tank

Postby bcassedy » Sat Mar 21, 2020 9:29 am

Some time ago I installed a 19 gallon holding tank for our 32' SB. You can find details at:

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Re: Plumbing for DC39 holding tank

Postby MetalHead » Thu Mar 26, 2020 2:56 pm

Here is a few of my 15 gallon tank install.

Key step is to card board template the area to see what tank will fit.
Tank Mounted - Copy.jpg
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