Hooking up directly to septic tank

[uscgvet]

Hello! My circumstances have changed (though I am ok) and I will be living in my parked RV at home for a while. I have a septic tank and an RV cleanout. I'm thinking of switching over to a residential toilet hooked directly to a hose to the cleanout. I searched this forum for "residential toilet septic" but didn't find anything directly applicable. Has anyone done this installation? Thanks and stay safe!

 

[Lou Schneider]

If the cleanout is in the line going from the house to the septic tank, your're good to go. Just make sure the drain line has a continuous downhill slope from the RV to the cleanout. You might also put a vent line at the RV end of the the drain pipe so the suction of the falling water doesn't suck water out of the toilet's P trap. 

Don't dump into the septic tank service hatch as baffles in the normal inlet direct the sewage properly into the tank.  Splashing it in from the service manhole will break up the scum layer at the top of the tank and send organic compounds into the leach field, clogging it.

If you were keeping the RV toilet and tank, you might want to hold off on doing laundry the day you dump the RV to offset the water the RV is adding to the septic tank.  A conventional washer uses 30 - 50 gallons of water per load.

 

[uscgvet]

Thanks Lou! I'm still not sure of the whole project - how do I connect the toilet directly to the drain hose? Is this a DIY project or something I need an RV repair person to do? Thanks!

 

[Rene T]

Do you plan on flushing the toilet and letting it go into the black water tank?  I hope that would work OK. One thing I would do is not use the typical flex hose. I'd use 3" PVC pipe. It has a smooth bore so less chances of anything clogging

 

[uscgvet]

I've been warned not to just leave the hose hooked up and the valve open, they say that the liquids will drain and the solids will form the "dreaded poo pile."

 

[NY_Dutch]

That's correct, dumping into the black tank with the valve open can very quickly build a "poo pile" big enough to plug the toilet drain. To convert to a residential toilet, you would have to remove the black tank and connect a 3 or 4 inch PVC line directly to the toilet mounting flange and pitched properly (1/4"/ft)  to the septic inlet. It may be possible to tie in the existing RV vent pipe from the black tank, but if not, a separate 2" vent pipe should be added up the side of the RV.

 

[Lou Schneider]

Unless you're not planning to ever move the RV again, I'd keep the RV toilet and tank in place and use the septic cleanout like the sewer in a full hookup RV site.

If you have a downhill slope from the RV to the cleanout, youcan leave the RV connected with the grey valve open so your sinks and shower drain directly into the septic.  But leave the black valve closed until the black tank is 1/3 - 2/3 full so there's enough volume to flush out the tank when you dump.

If you don't have a downhill slope to the cleanout you'll have to use something like a macerator pump to dump the tanks.

 

[SLOweather]

How long is "for a while"? I am in the same situation as you. So far 5 weeks, and it probably won't be resolved for 3 or 4 more months. I dump the black and gray tanks ~ once a week. I use plenty of water to flush solids into the black tank and have yet to have a problem. I also added a third slide gate valve to the combined dump outlet to allow me to back flush the black tank with gray water a few times at dump time.

Retrofitting a residential toilet is not trivial, and could be expensive to do just "for a while". Have you measured a residential toilet with a tank on it to see if it will even fit? Certainly, trying to fit one into my toilet room would make using it, accessing the sink, or accessing the under-sink cabinet uncomfortable due to the extra room the tank would take.

In addition, I think a residential toilet's drop may not line up with the hole in the floor.

Then, there is the additional task of connecting the gray water dump to the new black water plumbing, with appropriate venting to insure that dumping gray water doesn't cause unexpected venting back up through the toilet bowl.

 

[uscgvet]

Thanks, SLOweather. Is it possible to keep the RV toilet in place, and the water supply to it the same, just plumb from the connection to the black tank? (after removing same)

 

[NY_Dutch]

Thanks, SLOweather. Is it possible to keep the RV toilet in place, and the water supply to it the same, just plumb from the connection to the black tank? (after removing same)

Not recommended... The smaller amount of water that an RV toilet uses for flushing will not give the proper inrush to carry the solids down the pipe to the septic system. That's why it's always preferable to have the black tank at least 1/3 to a half full at a minimum when dumping. It could work if you always fill the toilet bowl quite full of water before flushing though.


It occurs to me that if you're just trying to avoid having to go out and pull the dump valve periodically, the simplest answer might be to just install a cable or motor operated dump valve with the control inside the RV.


https://www.amazon.com/Camco-Waste-Valve-Sewer-Systems/dp/B07GBBQR1W/


https://www.amazon.com/Valterra-E1003VP-Valve-Electric-System/dp/B004RCXC1G/

 

[grashley]

As I see it, there are two choices.
1. Leave things "as is" and ready for future camping.  Keep the black valve closed, and dump when it gets ? full.  Price: FREE
2. Remove black tank, install residential toilet, and plumb directly to the septic.  Price: $$  RV no longer fit to go camping.

If your complaint is a low seat, round bowl on the RV toilet, replace the toilet.  I replaced mine with a Domenic 320 series RV toilet that was an elongated bowl and "high" seat - a big improvement for under $200.  Check other vendors for better prices.

https://smile.amazon.com/Dometic-Standard-Height-Toilet-White/dp/B00HQEKGB6/ref=sr_1_1?dchild=1&keywords=elongated%2Brv%2Btoilet&qid=1589854798&refinements=p_89%3ADometic&rnid=2528832011&sr=8-1&th=1

 

[SLOweather]

The question that hasn't been addressed yet, as far as I can tell, is.. "Why do you want to do this?" And the followup question, which I alluded to in my first response is, "How long is "a while"?

The answers to those will help us guide you much better...

Thanks, SLOweather. Is it possible to keep the RV toilet in place, and the water supply to it the same, just plumb from the connection to the black tank? (after removing same)

 

[nando562]

@uscgvet I've read all the comments and everything makes sense the pros the cons. with that being said the only comment that I have for you is this.... I currently live in my 5TH WHEEL RV and to me living like that is like being camping 24-7 nothing less nothing more. I replaced the factory rv toilet for a residential toilet if you googled replacement for rv to residential you wont get any favorable results. but if you search smallest residential toilet you would get a variety of results and just measure from the center of your toilet to the back wall where the toilet is seating and you will find the right toilet. now there are many different measurements that you gotta keep in mind the nearest side wall or the cabinet and probably your bathroom door, so once you figure it out you will be able to chose the right one. the rest like the installation and the plumbing it is just a matter of reading and follow the steps to get a right connection to it.

 

[NY_Dutch]

@uscgvet I've read all the comments and everything makes sense the pros the cons. with that being said the only comment that I have for you is this.... I currently live in my 5TH WHEEL RV and to me living like that is like being camping 24-7 nothing less nothing more. I replaced the factory rv toilet for a residential toilet if you googled replacement for rv to residential you wont get any favorable results. but if you search smallest residential toilet you would get a variety of results and just measure from the center of your toilet to the back wall where the toilet is seating and you will find the right toilet. now there are many different measurements that you gotta keep in mind the nearest side wall or the cabinet and probably your bathroom door, so once you figure it out you will be able to chose the right one. the rest like the installation and the plumbing it is just a matter of reading and follow the steps to get a right connection to it.

The toilet in my motorhome has a ceramic bowl and a standard residential toilet seat. What is the advantage of converting to a residential toilet?

 

[_Rusty_]

A conventional washer uses 30 - 50 gallons of water per load.

All good advice. I believe a better number for water usage is 10~20 gal., depending on model. Our singer front-loader uses 6~10 gal. for normal cycle

 

[Domo]

I assume your "RV cleanout" is a correctly plumbed drain that goes into your existing residential septic line.

With a down-sloping slinky connected to the cleanout securely, you have a system that works by simply opening the valve every 3-5 days and allowing the black tank to empty and then close the valve (add some Simple Green into the toilet to freshen the tank as it fills in subsequent days before emptying in the future).

What's the harm in keeping it as simple as that so that you don't have to undo anything where you're going back on the road or want to sell the RV.

To me, bypassing/droping the black tank seems like a plumbing and insulation hassle I would not entertain despite my plumbing and carpentry abilities after having been a licensed contractor and owned several RVs over the years.

I may simply be naive and not understand the benefit you are seeking - in which case, I hope you can get it done quickly, easily and with low expense, my friend. Let us know!

 

[Kirk]

. I currently live in my 5TH WHEEL RV and to me living like that is like being camping 24-7 nothing less nothing more. I replaced the factory rv toilet for a residential toilet if you googled replacement for rv to residential you wont get any favorable results

Are you asking a question, or just making a comment? The author of the original post has not been back since Oct. of 2021. The subject may well apply to others.

 

[Domo]

Are you asking a question, or just making a comment? The author of the original post has not been back since Oct. of 2021. The subject may well apply to others.

Lol, dates got me again!!! Sharper eyes than mine, Kirk.

 

[Gary RV_Wizard]

The toilet in my motorhome has a ceramic bowl and a standard residential toilet seat. What is the advantage of converting to a residential toilet?

Elimination of the black water holding tank and the dumping chore.. Essentially, a residential toilet "dumps" every time it is flushed. On the other hand, an RV gravity toilet lacks sufficient downward angle in the outflow and sufficient water volume to send the effluent to the septic or city sewer line. [But an RV macerator toilet might?]

Some people find dumping the tank really arduous or obnoxious. To them, a residential flush toilet is akin to the Holy Grail.

 

[NY_Dutch]

Elimination of the black water holding tank and the dumping chore.. Essentially, a residential toilet "dumps" every time it is flushed. On the other hand, an RV gravity toilet lacks sufficient downward angle in the outflow and sufficient water volume to send the effluent to the septic or city sewer line. [But an RV macerator toilet might?]

Some people find dumping the tank really arduous or obnoxious. To them, a residential flush toilet is akin to the Holy Grail.

I missed that the black tank was removed. That does put a different light on it. As for dumping the tank being a personal problem, an electric valve quickly solves that issue.