Sediment in hot water on tankless system, from failing storage tank? need advice & referral in 98004

[Danspot]

I'm looking for some advice and a plumber referral for the Bellevue, Washington area, for an issue with our tankless water heating system and associated recirculating pump + storage tank.

We moved into our custom new home 16 months ago. Since we moved in, the master bath shower aerator has gotten clogged up with sediment about every 2 weeks. The particles are like sand grains, gray/black in appearance. It clogs up faster with hotter water, sometimes noticeable in just a few seconds. The same sediment appears in other faucets (kids bathtub, guest shower) but we use the master shower more often, longer, and hotter than the others.

The system consists of 2 Rinnai tankless heaters, a small Bosch storage tank (heated), and a recirculating pump that pulls water back into the Bosch.

We had the Rinnais serviced and checked the filters - no problem. We had the water tested by Culligan - no real problems. We had the city check the water hookup and flush it out twice - no impact.

I then turned off the heater in the Bosch and the sediment went way down, and way up when I turned the heater back on. I experimented with turning the recirc pump and valves around it off and on, but that didn't have a big impact on the sediment.

I believe the problem is in the Bosch. I don't know if it's an anode decaying or something else; it has been 16 months of regular use, with no catastrophic failure and no real change in the problem.

I'd very much appreciate any guidance and feedback on the problem and potential causes. But most importantly, I'm looking for a local plumber (Bellevue, WA 98004) with experience in tankless systems with storage tanks, who I can hire to come and debug and fix this.

The system was installed by the initial plumber but then he went out of business and the contractor brought in a new one. Neither of them had a ton of experience with tankless systems. I think the installation is correct, but would love to have a review of that as well.

Thank you.

Dan

 

[bostonDIY]

Hello Danspot,

...I came across your post while researching my own HW sediment issue.

We both have an identical setup. In my case, a single gas Rinnai and a Rheem 2.5 galon heated mixing tank, with a Taco recirculation pump on a dedicated HW return line. The HW circulation return is routed to the bottom of the Rheem, so that it does not trigger the Rinnai with a short fire every time it circulates the standby HW.

My system was giving Rolls Royce level performance for about 8 months all the way up until sedment (brown and white flakes 70/30) showed up in a kids bathtub. I traced it to the Rheem HW tank and took it out of the loop to prevent further sediment circulation.

I am wondering whether you were able to find the solution to your sediment issue.

Thanks for sharing any info!

Best,
Michael
Boston, MA