Septic Tank Size

[Spdracr39]

We are putting in a pad for semi permanent living. The bus has 60 gallon grey and black tanks. Obviously the grey will stay open but the black will be dumping 60 gallons in bulk every couple of weeks. Has anyone installed a septic tank just for the rv pad? If you have what size worked out for you?

[beenthere]

i was builder for 23 yrs. i built many rural homes .. the septic tanks are like 1000 gallon. its the drain field thats important. states have different codes for amount of sq ft for 1 bedroom or 4 bedroom. and depth of pipe kind of pipe like with a sock or just perforated. what kind and how much material per foot of pipe. in ND with our soils you can go up 4 feet deep. i never did that as i think it aerates better at like 30 inches. and never in a place that water collects. on downhill slopes you cant just angle pipe with slope as all the water goes to end it has to be level or stepped

[Gary RVRoamer]

If it is only serving the RV pad, you might get by with 500 gallon tank and a suitable sized drain (leach) field, but I'd go for 1000. I haven't priced the components lately but there used to be only a small difference in tank costs and everything else is the same anyway. Local codes may dictate the size anyway, but since it's not a residence you might get away with a DIY, no-permit installation.


Be careful with the drain field - it makes or breaks the system and soil type and terrain are crucial factors (see beenthere's post).

[Rambeau]

Spd...... did not say he was adding a drain field. If not hooked to a field how often are you willing to pay to have it pumped? Are you going to empty the gray into the tank also? Are you thinking of a seperate field for the gray water? If your going to dump black only and pump it then a 350 gal. tank will last over a month. Gray on the ground will work if you have space and no neighbors too ding you. Campground hosts are frequently faced with this dilemna in parks where the only sewer hookups in the park are at the host sites.

[jacwjames]

I would contact the county health/environmental department and talk to them. There may be a minimum size that would work for what you want. My guess a 300 gallon would be enough along with ~100 ft of drainfield but that depends on you perk testing. You will need a drain field unless you plan on pumping, which would be a pain. Depending on the county requirements this could be stone filled trench or composite type.



Also, if you decide to add a septic system I caution against using any type of RV Black tank treatment. I might play havoc with the septic tank.




I built a new house and had the septic installed in 2017. My wife does dog grooming and I wanted a large enough system to handle that plus the 4 bedrooms, so I opted for a 5 bedroom system which required a 1250 gallon tank and 550 of drain field (110 ft per bedroom). Permit cost $250

In my case the health department required a soil study meaning I had to hire a guy to dig a couple holes, look the soil type, and write a report (that I had to correct). The study cost $300.

Install was pretty straight forward, cost $6500.

I ran the lines to have an RV dump in the parking area that I excavated, I actually added a second one if we have visitors.

[alank]

My opinion would be that you would need a larger tank, which will require a larger leach field.
You are saying a 60 gal dump every two weeks, thinking only a small tank will take care of this.
The problem is that a septic system is a "trickle" system. Only a small amount of water normally trickles into the tank on a continuing basis, and trickles out into the leach field the same way. An operating septic tank is normally full of water and as 1/2 gal. trickles in, 1/2 gal trickles out to the leach field where it gradually soaks into the ground. A smaller tank won't have the capacity to take a 60 gal dump without filling the intake pipe and possibly flowing out your dump cap. If you install a 60 gal capacity intake pipe, to dump into, then it can trickle into, and out of the tank, then you should be good. Septics just aren't for high flow water volume.

Another thing about septics is that they operate on bacteria to digest the solid waste. If you flush disinfects down, that can kill the bacteria and stop the digestive action in the tank. A tank usually requires continuous adding of the bacteria agent.

[Spdracr39]

I will be adding a leach field and I know about using ridx and not killing the bacteria. The perk tester I called recommended not getting a permit since it is a second septic on property and only for the RV. I don't have an issue with that as there are no neighbors but I want it to work. I may request a bigger tank just because. I don't mind getting it pumped. Twice a year is better than once a month though.

[hohenwald48]

Tank size determines how long the stuff stays in the tank and gets broken down by bacteria. Field size determines how much effulent can be soaked into the ground.

If you use a tank that's too small you stand a chance of introducing raw sewage into the field lines. If you don't have enough field lines you can water log the field lines.

In most locations septic systems are pretty well regulated and designs are critical. Failing to properly size the system can pollute the local area and ground water with some pretty nasty bacteria. I would suggest you consult the local health department or whoever regulates septic systems in your area.

If your main concern is that it works properly that would be the best way to go. Septic permits are usually in the $100 range and you get a lot of design assistance for that price. If you're trying to sneak something past the regulations then ignore this post.

Nobody on here can determine field or tank sizing unless they have some knowledge about your soil makeup.

[clifford j]

Spd, I understand you are ok with just putting it in,,, I would search for a contractor who's experienced with septic systems , explain to them your plan and see if they will work around getting a permit. They will know local code.

CLIFFORD

[jacwjames]

Built a new house in the country so no city sewer.

Knowing we would have to have a septic system I did research. Most "experts" say that there is no need to use a RidX type product if you use your system correctly. Some of the recommendations I found were


Do not use a garbage disposal disposal to send food waste to the the septic system. It will not break down easily.


Limit harsh chemicals, I actually put a bypass in for the two laundry rooms I built knowing my wife uses bleach to disinfect dog stuff.

Limit water use, that is why I installed the largest tank I could find, to help offset my wife's high usage.

No RidX or equivalent.

If you do things right you won't have to worry about pumping for +10 years, or longer depending on specific circumstances. So spending a little more now for the proper size system may save you money in the long run.

[Ivylog]

I would tap into the existing house septic system, even if I had to use a macerator to pump to it, if it’s higher up from the RV pad. The grey water could go into a French drain (5-10’ of gravel in a 2’ wide trench) and once a week pump the black to the house septic.

In GA (clay soils) you can legally put 10 RVs (no washing machines) on a normal house septic system (1000 gallon tank). If you want separate system for the RV I would use a 275 gallons plastic tote and 3 sections of plastic drain field chambers.
https://www.plumbersstock.com/adsarc...RoCyxsQAvD_BwE

[clifford j]

IVYLOG,,, ha! I made up a 2 tote system, been three years now and working great. The design duplicates a cement tank. No washer/dryer on the system.

CLIFFORD

[Ivylog]

The Infiltrator plastic chambers are the best thing for drain fields, especially in clay soils. The OP is in AR (soils unknown) and no permit so $250 in materials and a small trackhoe for half a day... problem solved BUT tapping into the house system is the best choice.

[Gary RVRoamer]

alank is correct in his warning about overwhelming a too-small tank, though we could debate forever whether "too small" is 300 or 500 or 1000. His warning is the reason I suggested 1000 even though 500 is probably large enough. Just trying to be cautious.



For the reason alank cites, it's better to dump 20-30 gallons more often than 60 gallons every once in awhile.


Note that the black tank contents are already partially digested when dumped, so you shouldn't be putting a bunch of thick solids and paper into the tank all at once. It is, however, enough viscous fluid to add several inches of water to the tank until it drains off. Modern tanks usually have baffles to prevent the nastier stuff from proceeding directly to the drain field exit pipe, though.