I'm planning the Hill Top to Katoomba walk in the cooler parts of this year
Go very soon - Boxing Day has a top of 16, 27th December is 18 degrees.
In the nearer future going to walk down Roots Ridge then up to Scotts Main Range and will check out the water situation.
I do hope this is a walk for walkings sake - and not a reconnaissance. People who do reccy's bother me a bit, from taking a mate li-loing along the Wollangambe to decide if his 10 yo children could do the trip, as he couldn't 'quite recall the bits from the last time we did it' (he did struggle himself...), to those who drive Sydney - Wilsons Prom to think about kayaking Bass Strait - then pull it off soon after with relative ease.
Perhaps deposit water on your 'check out' walk.
I've read there are water holes along Scotts Main Range - is this so and is it drinkable? Hill Top to Katoomba - is it a mainly along fire trails and possibly a bit tedious??
There are those small earth dams of about 6m x 6m adjacent to the road, but conversation with your walking buddies, or being deep in thought will likely see you miss them. You will see some without trying. I tried looking on Google Earth for you; tree coverage hides these water places from the aerial photography. The appropriate topo map-sheet may show them.
The water should be drinkable - consider; filtering out the course stuff (if any) through a clean shirt/hanky/pantyhose, or let it settle out overnight in a spare pot - if you have one. Yet the amount will be less than one-litre anyway - use 4 to 6 drops per litre of betadine. A water-filter will likely clog, but may work, if water-filters are your thing. Note - some people are allergic to betadine. And the next statement will cancel out this paragraph - you will have no water concerns
I have jogged twice from the Nattai Flats to Katoomba over 2 days one April. Water taken from Yerranderie was enough to the place as mentioned towards the end of this blog;
http://www.gphipps.com/bushwalking/mitt ... omba.shtmlScott's Main Range has a reputation for being tedious, but when I was new to walking in the mid-90's I thought it great. That was on a 6-day Katoomba to Mittagong walk. The guy who organised that with the NPA lead it annually thereafter - over 9 days along the Kowmung River instead, and then up to SMR for a little bit into Yerranderie.
Live everyday as if it were your last... one day you will be right.