Disposal of Gray and Black Water

Stop at least weekly at a full hookup campground. Dump the black tank just before you pull out.
Public dump stations can range from free to 5 dollars.
If your single, black tank should probably last two weeks. Two of us and I dump weekly.
There is a free app showing dump stations.

The answer to your first question will depend a lot on your bathing habits, and other water usage. If you're wise with your usage, probably 4-5 days, depending on tank sizes.

If you're boondocking - Lots of FlyingJ/Pilot gas stations have dump stations that cost $10 to dump, if you're a RV Rewards member or a Good Sam member it's cheaper. If you're staying in a campground - Almost all of them have dump stations that you can use for free.

There is actually an app for smart phones that list dump stations near you, I forget the name but I'm sure someone will chime in with it soon.

Doug

steadyfreddy123 wrote:
As a single person intending to live full time in a motorhome, how often would I have to dispose of gray and black water?

Depends totally on tank size, and your consumption. If you take a long shower, wash a lot of dishes, and do laundry, probably every week. If you take fast wet down/scrub/rinse down showers, do very few dishes, and do laundry elsewhere, probably once a month.

Where can I (legally) dispose of gray and black water while on the road?

Some states have dump stations at their rest stops, but not many. Some Flying J truck stops have dump stations. Almost any private campground will let you dump for a fee, something like $5-10. There are also services that will come and do a pump-out for you. That may be cheaper than going somewhere if you add the cost of fuel to the cost of the dump. Cost of this service varies quite a bit.

How much does it cost each time to empty the tanks while on the road?

See above.

Few tips.
-Do dishes in a basin. Then dump the water in the toilet. Saves space in the gray tank. Also, helps with watering down the black tank.
-If you shower, carry a I gallon pitcher. Fill the pitcher when turning on the shower with the cold water the preceded the hot. Then use that water to flush #2's down the toilet.

Some municipal waste water treatment plants also accept RVs. The city next door to us does that.

As others said, it depends. First - try not to dump your black tank until it's at least 2/3 full. This will offer the benefit of physics to help flush everything out. If your black isn't full and you want to dump, add water to help add more liquid volume. If you are at a CG, then you can leave your grey open to drain into the septic- but do not leave the black open. If the black is left open the liquids will drain leaving solids behind and creating the dreaded "poo pyramid". So, black only when close to full, grey whenever - but it helps to have a full grey as well and dump this after your black to help flush the hose with cleaner, soapy water. Just keep an eye on your gauges. No one on here can say for certainty based on your habits how long it will take you to fill your tanks. But these general rules may help.

Here's a good website for dump stations - http://www.sanidumps.com/sanidumps_usamerica.php

We use about 8 gallons a day for two of us. That includes drinking water, cooking, cleaning, washing dishes, toilet use and showers.

Sanidumps also has GPS enabled iphone and android app.
I think the pay version will actually give you directions. we have the free version, it still shows us where we are and where the nearest dumps stations are, and can get details (type of facility, address, fee is any, etc.)

You need to dump black and grey at a location specifically designed to dump waste. That means you do not want to dump on the ground or into a street sewer drain. Campgrounds, many truck stops, municipalities, and RV dealers have (or can have) dump facilities available to you. How often you need to use these services will depend upon the size of your holding tanks and how judiciously you are able to use water.

Sometimes rest stops along the interstate has a place to dump. I've never used one but I think they are free.

For how often you'll need to dump, it depends on how large your holding tanks are. We could go 12 days before having to dump. Proper dump stations are all over the place so you won't have a problem finding them. The above-mentioned link is a good one.

If you're boondocking/dry camping many folks spend a night in a RV park or public parks (state, Corp of Engineers, county, city, etc) when it's time to dump and use their facilities for dumping and filling up with fresh water. It also gives you a chance to take a long hot shower and possibly do laundry.

If you don't want to go to a RV park there are many places such a filling stations and some rest areas that have dump stations. Also, RV parks or state parks sometimes will let you dump for a fee if you're not staying there.