Sparge water help

[sbond10]

I'm planning a brew for Saturday and this will be my first time using a mash tun I normally no sparge biab I just need a hand figuring out what water I need

Normally for biab
A grain bill of 4-5kg I use 36 litres total water to get 23 litres
I worked out my evaporation at around 20% on my gas burner

Saturday's brew will be just 4.3 kg of malt 60g of hops and 400g of sugar
My dead space in mash tun is approx 2 litres
I'm guessing I need 32 litres into the boiler
I'm planning a hybrid sparge by which I'll mash in with my required water wait 90 mins then start adding water slowly (is 80c too hot considering I'll be jugging it across)at same time have the tap open aiming to add and remove 500ml - 1 litre a minute until done.
I plan to check gravity every ten minutes and both mash and hlt temp to make sure it hasn't dropped to far

Anything else I've missed there and advice

Cheers sean

[lord groan]

Sounds about right. When I'm doing a 23litre brew I normally use about 32litres in total, 10-12l for the mash and I batch sparge with two lots of 10l, this gives me around 26-28l in the boiler depending on mash losses. Then i boil until it drops to between 24 and 25 left, which gives me about 23 in the fermenter. Boils run from 60-90 mins depending on the weather. Because I only remember the irish moss and putting the immersion chiller in the wort at the last minute, I often end up boiling a bit longer and lose too much from evaporation so I often end up adding a litre or so back to the fermenter to bring it back to 23. Your larger initial volume ought to cover that.
You're certainly not going wrong with this plan, you'll need to do a few brews to get the feel for how much you need.
good luck

[sbond10]

I keep thinking why am only using 32 but that's taking grain absorption into count as I'm doing a grist ratio 2.5 litre to 1kg of grain. So my first lot of water is 12 litres then sparge with 20 checking bits and pieces along the way.
I forgot to mention I'll be using my old biab to act as my filter and sending the first few litres back in until it clears