Bradford white dual system hot water radiant heat lines are building pressure

by Carlos Buhler
(Canmore, Alberta, Canada)

Background: We have a pretty standard 8 year old, 47 gallon, dual loop system, natural gas powered hot water tank. Our home is about 2700 square feet located in a cold area of the Canadian Rocky Mountains, Canmore, Alberta.

Our very cold incoming water temp is about +2 or +3 C off the street. Our hot water boiler creates hot potable water through one loop system and heats a second mix of water and glycol running through the sealed, in-floor, 2 zone radiant heat tubing in our ground level floor. One zone thermostat controls the garage in floor heat (an additional 450 sq ft.) and the other zone thermostat regulates our ground floor finished living area of about 1200 sq feet including a semi complete kitchen (we have no 220V stove; just a hotplate, microwave, and toaster oven. We have one 3/4 bath in that area on the ground floor, plus a washer/dryer in the garage for tenants.

A couple lives in this 1200 sq foot area We (a family of 4 w/ two small children) live on the raised level of this 2 level "single family" type home. We have a washer/dryer upstairs also, for us, plus a full kitchen, full bath and a 3/4 bath. The house also has a gas powered, forced air system which circulates warm air mostly through the upstairs area.

Problem: So far, everything is still working. BUT the radiant heat system lines are slowly gaining pressure over a period of several weeks. This is visible on the pressure meter which is normally at 12-15 PSI but climbs now to where it's maxed out at over 35 PSI. I have bled it off twice to bring the pressure back to the correct 12-15 psi but it climbs again.

I am beginning to assume that we have a pin hole leak inside our water heater's radiant heat loop which is allowing household water pressure to seep into the radiant heat line. But could it be something else that is causing this pressure gain, like a pressure relief valve failure between our household pressure and the radiant heat line? There appears to be a separate water line that feeds into our radiant heat loop, presumably to "top off" the radiant heat loop if it somehow lost pressure.

I probably have to replace the whole hot water system if it's a pin hole leak and am preparing myself for the worst. Yet, this means deciding how best to proceed to heat both the radiant, in floor fluid, and our potable water given the advances in the last 8 years.

Questions: What do you think is raising the pressure in our sealed, radiant heat line?
If I need to replace the hot water tank I have now, do you feel confident about these on demand, natural gas tankless systems (like the Rinnai RC 98 HPi interior condensing water heaters together with a three way mixing panel like the HEP Isolation Heat Exchange Panel made by heat link?
There are so many solutions possible out there, and I don't know where to begin!

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Feb 01, 2019
BW Combi Core
by: Steve

Our Nonprofit housing group built a townhouse style, a single storey apartment building with radiant in-floor heating in 2010. Each apartment is about 700 square feet and each has its own individual BW Combi Core unit. (So we own 18 of these damned heaters!) The repairs/replacement costs are horrendous. So far parts have been warranty but labour costs can be up to $2200 if the failure happens on a weekend or after hours. It is death by a thousand cuts. We are in process of getting quotes to start switching them out. It will not be with the same brand as they do not extend the warranty to the new old unit is replaced under warranty.

Oct 04, 2017
Pressure in Check
by: Gerry

The pump creates turbulence every time it works so there is a natural pressure change in the system. You should have a bleed valve you can function on the pressure tank on top of the system. You can install a set valve that has settings in the range you desire as well.

Sep 18, 2013
warranty only for original unit
by: Anonymous

re: warranty period has ended
That is what happened to us, as well. We bought our house in 2004 and unbeknownst to us, the Bradford White tank had been replaced under warranty already. The previous owner made mention of his "new hot water heater" as a perk of the house. Our home was built in 1997 so the first tank must have failed after 7 years. When I called in the serial number to BW, I was told that the replacement was under the original tank's warranty! I had to replace the whole unit with no warranty help. I expect this new one won't last more than seven years...

Sep 08, 2013
no 10 year guarantee on second replacememt
by: GKK In Cleveland

Had my first dual hot water tank go bad after 7 years - was replaceted according to warranty -- replacement went after 5th year and warranty does not cover - get this: is under warranty of first tank so past the 10 years -- NOW if your car is replaced because of a defect - Do You GetA New Warranty with the 2nd Car?????

Oct 31, 2011
another leaking Bradford White combi water heater
by: lew

I have a Bradford White combi heater, 12 years old. It has developed a leak in the radiant heat side exchanger, and I now see that there is probably no alternative but to replace it. I'm disappointed that it lasted only this long, especially since they are expensive, I got a quote for $3600 just for the heater, no installation. The heater worked great for its purpose until it sprung a leak. Is there a better replacement unit for the money? Or a better quality comparable unit?

Jan 31, 2011
Same problem - radiant heating
by: Craig in Mn

I have a 2003 BW combicor model.
It started bleeding domestic water slowly into radiant & now is full flow. My 30psi T&P valve on the hydronic side fills a 6 gallon bin in 20 minutes now. I'm told it's a failed heat exchange. I too thought it was the fill valve & replaced it. Nope! After researching, this is a very common problem with these early models.
The good news is that it's covered under the 10 year replacement hx warranty. Labor costs are not covered. Got a $750 quote. Seemed high. Getting another bid in the a.m.

Jan 18, 2011
radiant heat lines are building pressure
by: Jim Drew

Did you discover if it was a pin hole leak? My system actually went up over 80 psi, a new fill valve and expansion tank did not fix the problem.

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