My question involves landlord-tenant law in the State of: Washington (Seattle)

I have a question regarding a very high utility bill after a gas leak. Last week my housemates and I noticed a gas smell coming from the side of the house. After contacting the landlord about this,we were told that there couldn't be a problem seen that there had just been a new bowler installed. However, we kept smelling gas and contacted the gas-company ourself. They came over and discovered a small gas leak which they fixed the next day.

Yesterday we received our utilities bill from the last month and it was unusually high. We are convinced that this must be because of the gas leak. Can we demand our landlord to pay part of the bill or do we have to go to the gas-company?