Tankless water heaters need to be flushed annually to maintain peak performance. There are many kits available online, however because they are labeled "tankless flush kit" they are double or triple the price of putting one together yourself. I was able to put one together with commonly available parts that was 1/3rd the cost.
This flush kit was based off of the Rheem RTG20124 flush kit. I also followed the instructions that are supplied with that kit.
Follow the instructions that come with your tankless water heater. If you are unsure pay a professional to do this for you. Rheem's warning: Water Heater parts and accessories should only be installed by qualified technicians. Failure to understand and follow the manufacturer’s installation and use instructions may result in fire or explosion, electric shock, property damage, injury or loss of life. It is your responsibility to seek professional advice when installing and using these parts and accessories.
- 2.5 gallon bucket (I liked the smaller bucket so you don't have to use as much white vinegar)
- Washing machine hose kit (female garden hose thread on both sides)
- All plastic submersible pump (Superior Pump 91250 1/4 HP)
- Clamp to hold return hose in the bucket.
Flushing the tankless water heater will involve electricity and water, so make absolutely sure you keep the electrical connections dry and utilize a GFCI outlet.
I won't go into detail on how to do the flush as it is different for every tankless water heater. Remember whatever you use to flush is going to be in the potable water system of your house so use caution with the parts / cleaning solution (I used white vinegar) you use. Make sure everything is clean.