Your landlord has 24 hours to fix your water heater. You have to write to them (I know it sounds absurd but that is what the law requires) and recite the facts. Remind them that you advised them of the issue with your hot water, and their response was to shut it off, and not fix it. The statute gives them 24 hours -after you give notice - to get this fixed. The fact that it is a weekend is not relevant. Write the letter, keep a copy.
If they don't fix it in 24 hours, print out RCW 59 18 115 and RCW 59 18 085, and go to the City or the County's Building department with that copy of your letter demanding they repair the water and ask for an inspection. It really matters that you figure out whether you live in the City or the County; you can call and ask, the City or the County will know.
Read the two statutes, and then make the municipality do their job. If you get the runaround, contact Mike Long in Longview for assistance. He'll help you if he can. The remedy is three month's rent or $2,000 whichever is more, and any pre-paid rent you paid up front, and all your deposits returned within 7 days so you can fund a new tenancy at a place where the landlord takes maintenance more seriously.
And all your reasonable attorney fees. Hope this helps. Elizabeth Powell