Answer A : First, the MHCO Lease cited above addresses this. Not fixing the leaks, which are their responsibility to do, is a violation. Secondly, ORS 90.740(f) requires that tenants "(u)se electrical, water, storm water drainage and sewage disposal systems in a reasonable manner and maintain the connections to those systems. The tenant is using the water system in an unreasonable manner when they refuse to fix the leaks.
ORS 90.630 (Termination by Landlord) provides, in relevant part, the following:
(1) Except as provided in subsection (4) of this section, the landlord may terminate a rental agreement that is a month-to-month or fixed term tenancy for space for a manufactured dwelling or floating home by giving to the tenant not less than 30 days' notice in writing before the date designated in the notice for termination if the tenant:
(a) Violates a law or ordinance related to the tenant's conduct as a tenant, including but not limited to a material noncompliance with ORS 90.740;
(b) Violates a rule or rental agreement provision related to the tenant's conduct as a tenant and imposed as a condition of occupancy, including but not limited to a material noncompliance with a rental agreement regarding a program of recovery in drug and alcohol free housing... .
ORS 90.630 goes on to explain that you may issue a 30-day written notice of termination, allowing the tenant to fix the leaks within 30 days and avoid termination. If they fail to do so, you may file for eviction. If they cure, but the problem occurs again within six months following the date of your earlier 30-day notice, you may terminate the tenancy within 20 days, and there is no opportunity to cure. MHCO has the necessary forms.
Be sure you have papered your file to support your contention that these are water leaks for which the tenant is responsible, and then specifically describe the violations (there are two of them, one under the Lease, and the other under the statute) in the Notice.
Answer B: This question is same as the prior one and the answer is the same (although the placement of the requirement may not be in the same location, depending on the date of your lease or rental agreement). Just make sure you have the evidence (e.g. plumber statement) before acting, and that you adequately identify the problem and solution in the Notice.