No, don't buy junk.
I have two Gilmour garden sprayers. Each is 2 gallons capacity and both
have lasted me about 20 years so far. What I like about Gilmour is that
they make overhaul kits available. That overhaul kit contains all the
parts that normally wear out on the sprayer, so that you can overhaul it
every 10 years or so, and it works good as new again. There are
separate overhaul kits available from Gilmour for both the air pump and
for the pressure release valve.
'Gilmour' (http://www.gilmour.com/tank-sprayers/lawn-garden /)
Also, most Gilmour sprayers come with brass wands. Not only can you
replace the wand as a part, but you can solder a brass sprayer tip
holder onto the end of that wand to replace the plastic tip that's put
on it at the factory. Soldering a sprayer tip holder onto the end of
the wand allows you to change the sprayer tip in the holder for
different spray patters and liquid flow rates. You can have a flat
spray, conical spray or a jet for cleaning small areas at anywhere from
a very fine mist to a heavy flow rate. TeeJet is probably the biggest
name in spray tips. Their spray tips are plastic with a hardened steel
nozzle in them so they don't wear out unless you're spraying with
considerably more pressure than you can get out of a garden sprayer.
TeeJet makes all kinds of different spray tips for different
applications, and any place that sells agricultural spray equipment will
carry most of their line.
'TeeJet - Welcome to TeeJet.com'
Go to any place that sells agricultural spraying equipment and you
should find Gilmour garden sprayers, brass sprayer tip holders and
TeeJet sprayer tips.