Mysterious sediment substance clogging hot water lines

[heartland]

Hello,

We have had a mysterious problem for the last two months at our house. There has been a persistent flow of some sort of sediment that is clogging everything on the hot water side.

Our setup:
City water --> softener --> tankless heater

We also have a recirculation loop with a small 6 gallon tank heater that runs continuously with a small pump.

Our house was built in 2006 and the softener wasn't installed despite hard city water until 2015. The heater was a Rinnai R85.

I've attached some photos of the gunk that continues to be caught in the showerhead screens and in the screens in the valves of the Grohe fixtures.

The progression of problems has been this:
-initially recirculation loop stopped working.
-plumber looked at it and thought check valve was not working so replaces that
-still didn't work and plumber determined 6gallon heater not working
-replaced 6 gallon heater
-during this time noted that there was resin in toilet tanks and determined that softener membrane was bad and resin was escaping.
-softener to bypass mode
-no resin found in screens around house
-softener rebedded
-hot water flow worsened.
-part replaced in tankless heater
-flow and pressure in showers still low
-gunk / sediment continuously filling up screens and slowing flow. Flow great once cleaned then after about 20 showers it worsens again to a trickle.

I've checked the pressure from the city - 110psi

Pressure after pressure reducing valve and just after tankless is 70psi which is the same at the shower heads themselves.

We initially thought this could be from scale built up over a decade of not having a softener in the old tankless heater.

We ended up replacing the tankless with a Rinnai RE199IN thinking this may fix the problem.

The new heater works great but the problem persists.

After ten showers or so the flow slowly starts to decline to a trickle. Then when we look at the screens it's full of this stuff and clogged. We remove the sediment and the process starts over.

We've worked with some great, experienced plumbers but so far two of them are stumped.

Does anyone have any idea what this might be coming from and how to get rid of it?

It is gray/green color and not necessarily hard like I would expect calcium scale to be.

Thanks for any help!

 

[pasadena_commut]

The water softener may be leaking its substrate material. Look at it with a magnifying glass, does it look like little tiny balls (probably not perfectly spherical)?

That happened to one of my neighbors. The soft water service put on a defective cylinder which was missing the membrane which holds in the resin beads and it dumped most of it into his house in short order. It was a pain in the butt to flush it out of all the lines.

 

[heartland]

Thanks for your response!

So actually at the beginning of this process (and I don't know if it was cause or effect or completely unrelated) our softener membrane did go bad and they found resin in the toilet tanks. The plumber rebedded it, and I assume it's good as new.

It's hard to tell if they are spherical. It really doesn't look like that. But the sediment does almost disintegrated or at least squish down easily if squeezed.

Also, it does primarily seem to be coming from the hot water side and I'm not sure how that would be the case if it was more proximally causes by the softener since all the cold water is also softened.

Maybe this is helpfuI. I just tested something. I cleaned the screen then ran the shower in the basement on the hottest water for 10 minutes then removed the head and took this picture. I cleaned out the screen then ran it on the coldest water for 10 minutes then took this picture.

Does this mean it is coming only from the hot side?

Is there any way to check the integrity of the softener membrane/substrate just by looking at it?

Thanks again!

 

[pasadena_commut]

Hmm.

You have a small 6 gallon recirculating heated tank, which you replaced. Does it have a drain? If so flush it, and flush the whole recirculating loop. Don't just drain it, get a large flow through it for a a minute or so to blast everything out of the pipe and tank. That stuff looks like the sediment from a tank water heater. It is squishy when hydrated and dries to white/grey powder or flakes. (Maybe other colors if there is copper or rust in it too.) You probably got most of it when the old tank was replaced, but maybe there was a whole bunch in the loop which just settled out during that operation?

If you take water out right after it comes into the house, before the water softener, it doesn't have this stuff, right? There is usually a faucet right after the shut off valve.

If it is sediment it should dissolve in acid. Put a small amount in a glass container and cover with an inch or so of vinegar and wait. If it disappears then it was some type of sediment. If it doesn't it may just be remaining bits of the resin, which shouldn't dissolve under those conditions.

 

[heartland]

Thanks again for your reply!

I haven't had a chance to do any of that yet, but it sounds like the third plumber diagnosed two problems and fixed everything.

The first problem was the AO Scott 6 gallon heater. He said he sees this all the time -- the anode rod was sluffing off and clogging everything, even though it was brand new. All of the hot water went through that mini heater on the way to the rest of the house, and since it was hooked up at the bottom of the heater, it was dragging that stuff with it everywhere. That was problem #1.

The solution for that was to take out the 6 gallon water heater altogether. We still have an external pump for the hot water loop and the hot water loop itself. So what he did was disconnect the little heater, and we'll use the function on the RE199IN to flip the pump on and keep the hot water loop hot appropriately.

Also, he determined that there was a problem with the pressure reducing valve where the membrane would collapse or something and prevent flow/pressure after being on for a bit. Pressure from the city was 100-110 and the PRV brought it down to 75psi but it was malfunctioning apparently. That was problem #2.

The temporary solution was to remove the PRV for now as they don't have one in stock.

So, both problems (the PRV and the sludge from the anode rod in the mini heater) were contributing to low flow/pressure throughout the house, so much so that our dishwasher on the main floor also stopped working. Now it works great. The basement one was working, but maybe since it had a little more pressure being lower.

I am incredibly appreciative of this plumber as two other companies were completely flummoxed.

I do have one more question: Do we really need the PRV? The plumber said none of the houses in our area have one. I know code for an adjacent city requires one to keep psi to 80psi or lower. The Rinnai heater recommends 30-145psi but 30-80psi for "optimal performance" whatever that means. We don't have water hammer with this pressure, but I've read that higher than 80psi can cause damage to softeners and other fixtures/appliances.

Do you think it's worth adding the PRV back in?

I just wanted to follow up in case someone else encountered the same problem with these little tank heaters.

THANK YOU!

 

[pasadena_commut]

Wrong type of anode rod in the tank? Moot point now.