When solidary debtor who pays is entitled to reimbursement.
If a solidary debtor pays the obligation in part, he can recover reimbursement from the co-debtors only in so far as his payment exceeded his share in the obligation. This is precisely because if a solidary debtor pays an amount equal to his proportionate share in the obligation, then he in effect pays only what is due from him. If the debtor pays less than his share in the obligation, he cannot demand reimbursement because his payment is less than his actual debt. (Republic Glass Corp. v. Qua, G.R. No. 144413, July 30, 2004).