Hard work is "washed away" - Correct word?

Solution 1:

You may use wasted for a single word:

My hard work is always wasted by the client's repetitive changes.

Actually, the phrase down the drain is literally and figuratively close to your term washed away and means wasted.

My hard work is/goes always down the drain due to the client's repetitive changes.

Cambridge Dictionary:

down the drain:

If work or money is or goes down the drain, it is spoiled or wasted:

If the factory closes, that will be a million dollars' worth of investment down the drain.

wasted adjective (BADLY USED): ​

Wasted time, money, etc. is time, money, etc. that is not used effectively because it does not produce the result you wanted:

He wasn't in when I got there, so it was a completely wasted journey.

Solution 2:

How about nullified? There are two definitions of nullify in most of the online dictionaries and most of them are similar to this :

1 make legally null and void; invalidate.

2 make of no use or value; cancel out.

It seems to me that the second definition carries the meaning you are looking for.

See the Oxford online entry http://www.oxforddictionaries.com/definition/english/nullify

Solution 3:

"My hard work always goes unnoticed..."

Unnoticed — Cambridge

adjective, adverb Without being seen or noticed
"His contribution did not go unnoticed."

Escape notice — TFD

Fig. to go unnoticed; not to have been noticed. (Usually a way to point out that someone has failed to see or respond to something.)
"I suppose my earlier request escaped your notice, so I'm writing again."
"I'm sorry. Your letter escaped my notice."