We have two bathrooms, a guest and the master, and the guest has a bath/shower combo, but the master has a separate bath and shower. The guest has hot water flowing pretty consistently and the master bath has lava coming out the the faucet, but the master shower never has hot water. It's lukewarm at best. Any ideas as to why that is or what could fix it? BTW all the faucets have separate hot and water handles, except the master shower. I'd appreciate any suggestions!