While we haven't been permanent long termers on the road, we have spent almost a year travelling in ours.

We have two 80 lt tanks and with showers every day, washing up, cooking etc, the water will last about 3 to sometimes 4 days. We carry 4 x 25 lt plastic water cans in our ute which we fill up wherever there is potable (drinking) water and use a 12v submersage pump to shift the water into our van water tanks to avoid the lifting. We also carry a 4 way tap to use on shire buildings where they remove the tap top to stop vandals turning on taps and then just walking away. And most towns have free/cheap water at their Info Centres or ask at the Servos when you go in to buy fuel (ask before you fill up - never struck one yet that said no)

Unless you plan on a lot of free camping (and now days you often need a grey water tank because of by-laws or dirty looks from other campers will your grey water hits the ground), I would be using the 60 lt for your grey water.

Many free campers also have inexpensive filter/12v pump setups so they can take water from murky looking lakes, creeks etc and filter the water pumped straight into their water tanks

Washing machines churn through a lot of water - have a lot at the handbook for your machine and you will see just how much it will use. Showers - hop in, get wet, turn off the shower, soap and shampoo all over and then turn shower back on to wash off soap - you can have a good shower using only about 5-10 litres of water. It helps to have a water shaving nozzle and a shower with wall detachable flexible hose to quickly wash the soap off the more "difficult" parts of the body.

If you are in colder areas and don't need or want to shower every day - use a flannel and handbasin for a body wash or wet ones (the baby bum wipes)

We have 23' Jayco Outback. Has 2 x 95lt plus we have added a purpose built 60lt grey water tank that can be accessed to clean via (plumbing caps) that can be left off when not in use. Very very practical and works.

We also carry 24 x 600ml roughly 14/15 litres of bottle water. This can be purchased with your diesel {woolies discount} gives a cost of about $2/3$ for the water.We use both 95 litre tanks for all water needs and find the quality of water around the country will vary in taste. Thats where the bottle water comes in handy. We are virtually full time on the road and do not have issues finding/sourcing drinking water for the van.

JohnR

you can buy the 4 way tap handles from any Bunnings. But most of their staff wont have a clue what youre talking about, so be prepared to hunt through their Plumbing area - they are brass and attached to a cardboard backing. If you think you are going to take water from murky creeks or dams - many use two filters. The first (cheap as chips from Bunnings) is an in-line hose one to catch coarse material. These ones unscrew to wash out the debris caught in the mesh. The next filter is for the nasties and usually around 0.5 microns - again you can get these so they go in-line on your hose. We use a boat bilge pump - small and yet again, hose in line. But if the water is suspect, boil it well before drinking it even after filtering. And don't be mean and try to make your filters last for ever - its a quick way to end up in a painful or dangerous state in hospital !

The only other suggestion is carry two lengths of food grade hose (not garden hose). You will often find at Info Centres and Servos that you will need to connect the two together to get from the tap to your water storage. To stop dust getting inside your hoses, use the cheap grey plastic connectors that Bunnings have in their Retic area - buy a handful as theyre less than $2 each and join the hose ends together (also stops water in the hoses leaking out into your storage area. We use Velcro strips to hold our water and sullage hoses in a neat, round and tight bundle.