Two plumbing contractors based outside New York’s Westchester County are fighting a $25,000 fine for doing work inside the county.

Demonte Plumbing, which is based in Commack, New York in Suffolk County and PSI Plumbing works out of the Bronx are both asking the state Department of Consumer Protection and the Plumbing Licensing Board to annul the penalty.

According to a complaint filed in the Westchester Supreme Court, the plumbing companies’ owners say that plumbers tend to receive higher fines than other businesses that commit similar violations.

Bob Demonte of Demonte Plumbing and Thomas Ward of PSI have known one another and worked together for more than 35 years, according to their lawsuit, and when they formed a joint partnership to bid on a job in Greenburgh, New York, they believed only one of them needed to be licensed in Westchester.

After starting a job last summer and receiving a plumbing permit, local inspector determined that Demonte, and not PSI, was paying the plumbers. Last November, Demonte and Ward testified at the plumbing board hearing that they believed they had acted properly, but admitted that they did not know how to properly undertake the joint venture.

The board ruled against them and fined them $2,500 each day for five days.

The two tried again at another board hearing last January. Their attorney said that while an official schedule of fines authorizes a fine of $500 to $5,000 per day for operating without a license, the schedule also recommends a fine of $1,000 per day for the first offense. The attorney also argued that companies that are, in fact, based inside the county, face much smaller penalties for operating without a license.

The board chairman said the fine was justified since the work was commercial and showed a “fine sheet” that did distinguished between residential and commercial work. The plumbers’ attorney continues to argue in the new lawsuit that the difference in fines between commercial and residential work was never approved by the board or filed with the county clerk.

The plumbers want the court to set aside the fines or reduce them to the amount recommended in the official schedule.