Every Landlord, from whom any Part of his Rent has been deducted on account of such Drainage Rate, and who is himself liable to the Payment of Rent, shall be entitled to deduct from the Rent payable by him such Proportion of the Sum so deducted from the Rent payable to him as the Rent payable by him bears to the Rent payable to him, and so in succession with respect to every Landlord receiving Rent, and also liable to pay Rent on account of such House or Building; provided that no Landlord, being also a Tenant, shall be entitled under this Provision to deduct from the Rent payable by him more than the whole Sum deducted from the Rent payable to him.