Septic tank RV dump

hammick · 08-29-2015, 09:17 PM

We are building a barn on our remote property in Montana. The septic tank is being installed as I type this. The installer put a 4" clean out pipe uphill from the tank to use as an RV dump. It has a cap on it that he says I can just tap off with a hammer or mallet.

Will my standard RV dump hose fit nicely into 4" schedule 40 PVC or do I need to get some type of adapter? We are heading up to the property in about two weeks and I would like to have what I need as it's a couple hour drive to the closest hardware store.

Thanks.

rockfordroo · 08-29-2015, 09:24 PM

Here'a a PDF with the pipe and fitting dimensions. Compare it to your sewer hose connection.

I think what you see in campgrounds is 4".

**Flybob** · 08-29-2015, 09:24 PM

If you hose has the tapered adapter on the dump station end, you will be fine. If it has the bayonet connector, the tapered adapter is needed.

trbomax · 08-29-2015, 09:25 PM

I used a 4" threaded cleanout on mine.When I poured the concrete around it I made the finished top of the concrete about 3" above the top of the cleanout cap.I did this so as to not snag it with the snow plow and to be able to drive over it without putting any pressure on the plastic cleanout cap. My 90 deg hose end fits nicely.A stinky slinky would not w/o a 90 deg end on it.

hammick · 08-29-2015, 09:29 PM

Thanks guys. I have the tapered connection that I usually put into the hinged dump hole at the dump station. Photo of work in progress attached.

My trailer and dump hoses are on the property which is 1,100 miles away from home so I can't measure.

Sound like I'm good to go. I need a tight connection because if it slips off I'll be dumping a lot of dookie next to the living quarters of my barn. Wife might have a stroke

Oh and I think I am going to have them move the dump T closer to the tank. It looks real close to the door opening.

trbomax · 08-29-2015, 09:37 PM

I hope thats a sweeping "T" and not a std 90 deg one.Another thing is that you are dumping into a run and without some provision for venting on each side it will burp and could suck the traps empty in your building.

hammick · 08-29-2015, 09:41 PM

Quote:

Originally Posted by trbomax

I hope thats a sweeping "T" and not a std 90 deg one.

Not sure as I've only seen the photos. I am speaking with the installer tomorrow before he back fills the trench. I'm going to ask him to move the dump closer to the holding tank.

Is the concern with a 90 degree that it will clog under the pressure of the dump?

Is there are any other concern for sucking the traps then getting odor into the barn? I'd probably run water in the building when dumping the RV to help things move along.

The guy has been installing septic tanks for decades and says he always installs RV dumps like this.

I need to figure out any problems quick as they are finishing the job tomorrow.

Thanks for all the advice.

trbomax · 08-29-2015, 09:47 PM

The concern is that sewer gas will run back into the building thru the empty traps,and no plumbing code in the world will approve this design.A std "T" will clog and back up and w/o provideing proper venting the dump line will burp,spewing sewage out the top.

hammick · 08-29-2015, 09:51 PM

Quote:

Originally Posted by trbomax

The concern is that sewer gas will run back into the building thru the empty traps,and no plumbing code in the world will approve this design.A std "T" will clog and back up and w/o provideing proper venting the dump line will burp,spewing sewage out the top.

I am remote with no codes and no inspections. My builder is great but he is not doing or involved with the septic.

I'll ask the installer whether it's a sweeping T.

What kind of vent is needed?

Will it work as installed if I dump the black slowly?

trbomax · 08-29-2015, 09:56 PM

I guess to explain this in a more simple way,that dump needs to be vented within 6' UPSTREAM and vented again no more than 10' DOWNSTREAM. I avoided this delima by putting in a dedicated 500gal tank and 80 linear' of field.My dump is directly in the top of the tank,eliminateing the need for any vent stacks.

trbomax · 08-29-2015, 09:58 PM

Dumping the black slowly will leave the solids in the tank.The black tank in your RV depends on velocity to empty the solids.I understand the "out in the country so no permit" thing completely,but the codes are written to ensure that a system works,not just to sell more pipe.What your guy is doing would be fine for a cleanout ( which is also reqd),but thats not what you are useing it for.

hammick · 08-29-2015, 10:09 PM

Quote:

Originally Posted by trbomax

I guess to explain this in a more simple way,that dump needs to be vented within 6' UPSTREAM and vented again no more than 10' DOWNSTREAM. I avoided this delima by putting in a dedicated 500gal tank and 80 linear' of field.My dump is directly in the top of the tank,eliminateing the need for any vent stacks.

My tank is 1000 gallons with 113 linear feet of drain field. Does that change anything?

hammick · 08-29-2015, 10:16 PM

Quote:

Originally Posted by trbomax

Dumping the black slowly will leave the solids in the tank.The black tank in your RV depends on velocity to empty the solids.I understand the "out in the country so no permit" thing completely,but the codes are written to ensure that a system works,not just to sell more pipe.What your guy is doing would be fine for a cleanout ( which is also reqd),but thats not what you are useing it for.

Makes sense. Basically he told me he would put in a clean out that could also be used as an RV dump. I'll quiz him down tomorrow. Thanks!

trbomax · 08-29-2015, 10:18 PM

No.My tank is for the RV only. I have a 1500 gal tank and field for the house black water and another 500gal tank and field for house grey water. Your tank is common to the house and RV.It is a requirement to vent any line dischargeing into the tank inlet line.You only need a 1.5" vent "T" on either side of your dump line (upstream and downstream). This 1.5" vent stack only needs to be 6" above the flood grade at its end,meaning that where it comes out of the ground it only needs to be 6" above grade.Put 2 - 90 degree "L's" on the top of each vent so as to keep dirt and debris from entering.

trbomax · 08-29-2015, 10:28 PM

One more thing,I would check closely that your main line to the tank has 1/4" per foot drop for its entire length,no humps or low spots. This is critical because when you dump your RV its like flushing the toilet in the house 100 times all at once. Sewer draind are designed to float solids along to the tank and you dont have anywhere close to enough water going thru the line to properly do that. Any highs or lows are a perfect spot to build a clog,it must flow freely over its entire length.

trbomax · 08-30-2015, 10:00 AM

this is how I protected the dump cap.

hammick · 08-30-2015, 10:01 AM

Got more info this morning. The clean out is on a swept connector. The said it will be a little below grade and I will need to glue an adapter of my choice to it. I think I will use one of the 4" screw caps and then put a sprinkler box over it at grade level.

I'm going to give it a shot dumping without vents installed. Plenty of people successfully dumping their black water into their septic clean outs without vents.

If I need vents I'll be back for more info. Thanks for all the advice!

beechjet16mf · 08-30-2015, 12:15 PM

When we installed our septic system, our plumber installed a sweep clean out and a 4" threaded cap. Our sewer hose 90 elbow screws onto that, and it works very well. It is vented through the vent stack. Haven't had any problem for two years with the system.

HikerBob · 08-30-2015, 01:13 PM

If you can, be sure that you have a tilted slope on which to park your RV/TT at the time you dump. This will increase the velocity of the sludge exiting the black water tank. I use the septic clean-out that's near the house. It's a sweep so sludge enters the main line easily and goes directly to the septic tank a few feet away. I didn't have a natural tilt to the land, so I built a little 12 inch high ramp and pull my right tire up on the ramp to dump. Slick as green owl dung!

Roger2650 · 08-30-2015, 04:31 PM

Master Plumber here..........You can dump the black & gray tanks into the 4" threaded fitting without any problems. Your vent is on top of the camper, which is upstream of the black and gray tanks. I would install another drain opening closer to the septic tank. I'm sure that the "T" is a sweep tee because the clean out is for cleaning with a sewer machine, which needs the sweep to clean the pipe to the septic tank.
Roger

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