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Pile of rust from heated slab tubing, filter questions.

kgrant Member Posts: 13
Look at this pile of rust that came from some QEST Polybutylene tubing.

I'm helping a friend who had low flow in his heated slab last winter.

We tested the glycol in his system, it was very clean looking, tested at 30 degrees above zero, ph of 7 and burned your nose. Decided to flush system and add new glycol.

I flushed 200 gallons at 10gpm through each zone (4 total in the floor), alternating flow direction every 20 gallons and was still getting flakes of debris out.

I want to install a magnetic dirt filter, but I'm not sure the best place to install it.

I've included a picture of the boiler and piping. The two lower pumps are for the slab, the upper is for two unit heaters. There is another zone that comes from a separate building. And on the right is pipes that go to a heat exchanger connected to a coal fired furnace.

The only dirt in the system was in the floor, the rest of it was clean. The only place I see to install a filter is on the horizontal return pipe from the unit heaters and shop slab, but that won't filter the fluid from the house. I can't find a vertical filter for 1 1/4 pipe, did I miss one?

Fairbanks, Alaska


  • Ironman
    Ironman Member Posts: 7,350
    I'm surprised that there's any flow through the slab at all. The piping of the pumps and mixing valves is incorrect. The pump MUST be piped so that it draws from the " MIX" port of the valve and then pumps towards the floor.

    The fixed temp mixing valves are actually not the correct device for controlling a heated slab due to its high mass. A smart valve or variable speed injection mixing with ODR should be employed. Go to Tekmars site and look up their essay on injection mixing for a detailed explanation.

    The pile of rust was once part of the boiler block, which obviously it is not now. It's being caused by the lack of an O2 barrier in the Qest tubing. A heat exchanger, with stainless steel pumps needs to be installed between the boiler and the Qest tubing. Otherwise, more of the boiler block will be deteriorated until it finally begins to leak.

    A magnetic dirt separator can be installed in the boiler return line. It will require some re-piping.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rod
    hot_rod Member Posts: 21,872
    The Caleffi NA 5453 can be used in either position. The 1" version has a 19 Cv, so 19 gpm with a 1 psi drop.

    You have good isolation valves, be sure to power flush every loop for 20 minutes, that sludge can eventually plug the tubes completely. High pressure, high flow to move the solids out.

    Also a better mount for that large expansion tank.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Rich_49
    Rich_49 Member Posts: 2,766
    edited September 2015
    You could try a Caleffi 5453 magnetic separator or a Fernox TF1 . The Fernox's magnet will stick to your hand with a piece of steel to the other side of the hand and goes right through the center . Either of these , I believe can be located vertical , which would put them right front and center on the return pipe . Fernox also makes a canned restorer and inhibitor that easily are introduced right through the TF1 or the Caleffi it would seem . These are F1 Express and F5 Express .

    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • RobG
    RobG Member Posts: 1,850
    You said that there is a heat exchanger for a coal fired boiler? Is there one for the oil fired boiler?
  • kgrant
    kgrant Member Posts: 13
    Thanks guys. We're not in the position to be doing a bunch of repiping on the system. I just wanted to get a filter in there. Today's project is pulling the pumps apart to see if the impellers are plugged.

    There is a dhw coil on the boiler for the shop dhw, and an indirect water maker in the house.

    The hx at the coal fired boiler is a brazed plate exchanger. I cleaned it out. The coal side was dirty, the oil boiler side was clean.

    I don't know the age of the shop compared to the boiler or house. The house has proper pex in the floor. I'm thinking the shop is older than both.

    I'll just afraid that since I disturbed all the crud in the floor that now that stuff might make it to the rest of the system.
    Fairbanks, Alaska