So, how low can a lone monoflo go?

[Deleted User]

Hot water doesn't LIKE to flow down hill, and cold water doesn't like to flow up hill. If you only had one tee, you may get SOME flow, but probably not enough to do you a whole lot of good. If you had to flip a coin to figure out which tee to put the fitting onto, I'd go with the return tee because at least that water will be more dense than the supply...

Adding a TRV to the mix would probably cancel the flow allowed by the single one pipe fitting you would have.

As for checking a radiator prior to purchase, why not drag your own test equipment along. We have a policy of not moving any used radiators until they withstand a quick pressure test. Once tested, we hire a professional moving company to move the radiator into place and perform another pressure test prior to connection to the system. If the radiator doesn't hold pressure, the problems goes back to the moving company for improper handling. Haven't had to enforce that rule yet, but our moving company (Student Movers) understands our policy and complies.

ME

Dave_4

What's the downward reach w/ single diverter tee on return?

Do you suppose that a 5' spacing between 1.25" black tees would drive down to a cast iron rad? The single pipe would be running horizontally 4' above the ground and a 3'x3' rad would likely be used - directly below the 5' spaced tees, with the rad elevated 6" or so on insulated blocks. With the branch piping in black 0.75" do you think it would get the radiator any low quantity of heat?

I'd like to add to my heating equipment collection. I may get two rads and try out TRVs. One for the mechanical room to replace the feel of the oil steel boiler and the other one if I can get the drop. Sad part is it had double tees until my boiler swap - I wanted to tuck the crawlspace convector up into a joist space and had the first tee replaced with a regular one.

So would it flow?

Also... what should one look for in used rads?

I saw a couple on Craigslist. I'd like give some nice old iron a new lease on life. I have no idea what to look for when I check them out. They won't be pressure-tested and they'll probably be around $50 which is unreal for their worth. Any tips on what to look for without doing pressure testing?

Dave_4

Thanks, and I know she's always right...

I only want to divert water down 3'... not the typical 7 or 8. It never hurts to try if others can learn. There's a union nearby and a spare div-t if it fails. The existing div-t is on the return.

Thank you kindly for the the advice. What size fittings would I need to do an air test on most rads? I'll have to get a schraeder valve on one of them.

[Deleted User]

It depends...

Most radiators come from factory with 1-1/4" tappings, but are usually bushed down to something smaller, and any attempt to remove the 1-1/4" bung usually ends up being a long drawn out battle.

They make some great rubber thumb screw plugs of typical pipe sizes that will hold against reasonable (less than 30 PSI) pressures. The typical vent connection is 1/8", which is a great place to put the schrader valve.

When we test a typical 2 port radiator, we plug one port off, put the test gage on the other port, and charge the air in through either the vent port if available, or the schrader valve on the pressure test rig.

We have a box FULL of all the different tapping sizes seen (1/2 thru 1-1/2") that we take radiator shopping...

Is the union between the tees? If yes, make a small restrictive orifice to go in the union to act like the inlet tee. Or do like Robert Bean does and grab a pair of large channel lock pliers and squeeze the pipe flat between the tees to give you some restriction between the tees... Or was that John Barba that taught me that trick :-)

ME