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Heat in Remodeled Bath

I have an old home in the northeast. heat is oil hot water. big radiators in each room. I renovated the 2nd floor bathroom, took out the radiator and put 1/2 pex in the floor. ran the pex down into the basement and connected each end to the inflow and outflow of the line that went to the radiator in the renovated bathroom. I was hoping the flow would travel up and through the pex, but it doesn't. There are 2 different styles of piping for the heat in the house. The older style for the old radiators and the single loop for the newer baseboard heat in the newer portion of the house. What options do I have to get heat to the bathroom.
Mark Z

Re: Heat in Remodeled Bath


We would need a little more information as to exactly how the new bathroom radiator/PEX circuit is piped before we can determine why there is currently no hot water flow thru the new PEX circuit----the radiator you removed to put in the PEX circuit almost certainly had a BLEED VALVE on it; there may be a way to add a bleed valve to the new PEX circuit, but first, try the steps below.

Ordinarily, one can assume that if the previous radiator was working, and producing heat, we can assume that the newly installed PEX circuit should work as well, so you will have to examine the piping arrangement to determine what happened & if the new PEX circuit was installed correctly---the first thing that comes to mind is that the new PEX circuit is AIRBOUND (a common occurrence in newly installed HW circuits)---in such a case, if the other radiators in the system connected to the same branch/zone as the PEX circuit have shutoff valves, try shutting off the other rads to force water thru the bathroom PEX circuit to drive the air out of the piping---there is usually an automatic air vent in the piping near the boiler that will then eliminate the air from the piping.

If THAT doesn't work, some HW heating systems have what's known as PURGE VALVES (look like regular faucets) on the large supply/return piping near the boiler---you may be able to connect a drain hose to the RETURN PIPE, put the other end in a bucket & close off the return path to the boiler & "purge" the air out of the bathroom loop by turning on the "fast fill" lever of the water feed valve near the boiler.

The site below demonstrates the several possible "circuits" that are used to get hot water to flow thru different parts of the house when the T-stat calls for heat, the boiler comes on, & the circulator pump at the boiler starts pumping hot water through the piping system.

Please post back to advise if there are any VALVES connected at the point where you removed the old piping & attached the PEX tubing; some HW systems have what's known as MONOFLOW tees that direct the HW up to the bathroom circuit---does your system have these???

Monoflow tees have the word "monoflow" or "venturi" on their fittings, or have water-flow direction arrows (--->)(<---) or have "supply", "return" printed on them.

Seeing that you put in 1/2" diameter PEX, what was the diameter of the old rad piping, & what is the pipe diameter of the other existing radiators in the circuit, if they are larger than 1/2", the flowing water may see this as a flow restriction in the PEX circuit & bypass the bathroom circuit.

Since you have separate baseboard piping circuits and rad piping circuits in the house, is this done with zone valves or zone circulators???

Any photos you can post would be very helpful.


Re: Heat in Remodeled Bath

Hi Pelton
Thanks for your help, I think I answered all of your questions. Let me know if you need anything more.

Your probably right thinking it's air locked. I didn't think to install a bleader valve in the pex.

There are no shut offs on individual radiators. There are bleader valves on each.

There are 2 types of piping. The old section(the one I tried to connect the pex to) is " 2 pipe Reverse Return"

The newer portion is "1 Pipe series Loop"

The pipe diameter is 3/4

Could I connect to the "1 pipe series loop" section? Or would it be too much pressure going from the 3/4 heating lines to 1/2 pex?

There is a shutoff where the pex joins the existing 2 pipe system.

The 2 systems are run by 2 zone valves and 1 circulator

Thanks for your help

Re: Heat in Remodeled Bath


Since you already have zone valves set up in your piping system, and in view of the difference in pipe diameters between the 1/2" PEX & original 3/4" piping, my thinking now is leaning towards simply adding a new zone for the PEX bathroom circuit---this would give the bathroom its own T-stat, & more importantly, you would be able to control the amount of heat for the bath flooring & the personally adjustable higher temps almost always needed for those cold winter mornings when a family member steps soaking wet out of the bath---the bathroom has to be comfortably warm enough to satisfy the bather, & that can usually only be done with a combo of a zone valve & a dedicated T-stat for the bathroom.

Zone valves with a T-stat are surprisingly inexpensive---figure $60 for the valve & $30 for the T-stat (consult the Yellow Pages under Heating Equipment & Parts to find a hydronic parts house in your area; you will usually get a much better price there)---it sounds like you've been doing this work on the heating system yourself, so I don't think you will have any problems doing a zone valve install---my preference is for the Taco 570 series ZV, because I've had good luck with them, but you can always use the same brand you have on there now.

The other less intrusive attempts to get good heat out of the bathroom PEX would be to 1) try to install a bleed valve in the PEX circuit by shutting down the boiler, draining a quart or two from the boiler drain valve & cutting open the bathroom PEX & inserting a Tee with an extended 6" to 12" vertical with a bleed valve to get the air out---this may restore HW circulation in the PEX circuit, but I have my doubts that you would get enough HW circulation to make for a comfortable bathroom; always think of pumped water in a HW piping system as HAVING A MIND OF ITS OWN---as it travels thru the pipes, the water is always thinking of TAKING THE ROUTE THAT OFFERS THE LEAST AMOUNT OF RESISTANCE---its only thought is to get back to the pump as quickly & as easily as possible---therefore, when it travels thru a 3/4" pipe & comes to a "fork in the road" & has to decide between going thru a 3/4" pipe and a 1/2" pipe (which has more resistance), it will always take the less resistant route & go thru the 3/4" piping; 2) sometimes a monoflo/venturi valve ($2, heating supply stores) is connected to the takeoff between the 3/4" piping & the 1/2" PEX ---this forces more resistance in the 3/4" line & the water will flow thru the 1/2" PEX line---this is another possibility you can try before installing the zone valve option.

3) as you mentioned in your post, it is possible that you could attach the PEX circuit to the newer one-pipe baseboard loop---but it's hard to predict if this would work for you---you would definitely get circulation in the PEX loop, as well as the baseboard loop, but it may slow down the heating response in both loops when everything is added together----PEX bathroom loops are designed to function as a lower temperature RADIANT loop, where the lower heat of the PEX pumped water is pumped for longer cycles at lower temps (approx 100-120 degrees) than the HW in the rest of the boiler loops (approx 160-180 degrees); in some cases such high HW temps could damage the bathroom flooring over time, so the orthodox way of installing a PEX radiant loop is to also install a 3-way mixing valve in the separate bathroom zoned/t-stat loop that mixes the 160 degree HW with the cooler RETURN water that has surrendered its heat to the rads & baseboard----this approach almost always results in much more expensive components & piping schemes, so it may be best to try a simple zone valve/t-stat loop to resolve the issue.

Did you install your PEX bathroom loop sub-floor, embedded in cement, or did you install the PEX "under floor" in the underside floor joist cavities with aluminum deflector plates & batt insulation???----the "under floor" approach should give you less chance of damaging the finished bathroom flooring & you should get by without a mixing valve & being able to use the higher HW temps without problems.

Let us know how you make out on this project, or if you need further help; there are TONS of articles written on the internet concerning radiant sub-loops, especially BATHROOM radiant loops that can be done with an easy take-off from any HW boiler heating system.

Google "A Little Floor Warming Please" by Siegenthaler (who always accompanies his articles with piping diagrams); and also "The Plain Vanilla System" by Gallipoli; also Google "Bathroom Hydronic Radiant PEX Loops".

Re: Heat in Remodeled Bath


I'll take your suggestion and add a zone.

Your correct in your assumption that I would do the work myself.However, while I've taken a shot at most any home project, I stay away from Heating and Spackling. I installed the PEX but had a plumber make the connections. I'll give him a call to add the new zone.

The flooring layers are: 1/2" subfloor; 3/4" plywood, routered for the PEX; 1/2" cement board then tiles.

Thanks for the help. You were very helpfull. Thanks again

ps...I'll let you know how it turns out

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