Unfinished payment for a contract

Dear sir,
I just want your advise regarding a contract that i had with a client regarding swimming pool construction. The contract stated that payment terms are:
25% upon signing the contract <--paid
25% completion of milestone 1 <--paid
25% completion of milestone 2 <--paid
20% completion of milestone 3 <--paid
5% test run <-- not paid

The contract also states a warranty clause:
Five (5) years guarantee on the structural work and one (1) year on the finish and (1) year on the equipment against factory defect except for any damage caused either directly or indirectly on the part of the Owner and the natural forces like floods, storms, earthquake,and similar acts of nature. This guarantee is null and void unless all monies owing by the Purchaser/Owner are paid in full. The ancillary equipment remains the property of ***my company*** until all monies due are paid.

After using the pool for many months without paying the last 5% payment, client complain that there was a leak. The warranty clearly states that unless all payments are paid in full, warranty is not applicable in this case.

I would really appreciate your opinion on this. Thank you very much.

Business and profession wise, magandang silipin mo at tingnan kung pwede pang maayos yung leak daw. If you can repair it for less than 70 thousand pesos and save your reputation as a good contractor, well and good. Sayang yang kliyente mo. Maybe u can talk/think about repairing the leak so u can collect the remaining 5%. "Talo ako dito sa kontrata natin ah." "Baka naman may kapatid/kamag-anak/kaibigan kang magpapagawa ng swimming pool, irekemenda mo naman ako dahil inayos ko kahit talo na sa kontrata?" "Para naman mkabawi ako di ba?" sabihin mo. Diskarte lang yan pre'.

If after you have done your best and still u cannot save your good relationship with your client, then that's the time for you to consider a lawyer. Maybe the lawyer is a better friend.

Sya nga pala, pray first before jumping into an unfamiliar situation. God bless you and your "generous?" client.