Petiepooo
Computer
- Mar 3, 2016
- 2
My father has an interesting problem I thought someone here might have some insight into. He has a home heating system that pumps non-potable groundwater through a heat pump for heat. The problem is that it ices over sometimes due to a slight leak in the drain cutoff valve. I have an idea to prevent it but need a little help on the math.
The drain after the exchanger and cutoff valve is a horizontal run of about 20', a rise of 6", a slight down slope for the 10" as it goes through the wall, and a vertical drop of about 3' before it empties into a larger drain out to the drain field. At a cycle end, a soft-closing valve (so no water hammer) shuts, and the exterior portion of the pipe drains and all is well. However, the valve tends to leak, and if the water dribbles out of the exterior portion, the section through the wall freezes up in cold weather.
He's looking for a way to drop the level behind the high point by a couple of inches on cycle end so that a small leak in the valve won't dribble water into the external run. It's about a 50% duty cycle during the coldest weather, so it doesn't have to drop it much.
My thought was to put a check valve at the bottom of the 6" vertical section just inside of the wall. That check valve would draw air into that section just as the valve closes and the exterior vertical section empties creating a temporary suction. That check valve would have to draw air from outside, since if the drain does still freeze over or gets blocked for some reason, and the check valve fails under pressure, we don't want it spraying water inside. Plus he would want a long enough run that the air approaches room temp before it hits the check valve so that it doesn't freeze inside too.
My questions: Will it work? And will that 3' of vertical pipe produce enough vacuum to pull in sufficient air? My research tells me it will start at about .1mil, decreasing as it drains, but this isn't exactly my field. Thoughts?
The drain after the exchanger and cutoff valve is a horizontal run of about 20', a rise of 6", a slight down slope for the 10" as it goes through the wall, and a vertical drop of about 3' before it empties into a larger drain out to the drain field. At a cycle end, a soft-closing valve (so no water hammer) shuts, and the exterior portion of the pipe drains and all is well. However, the valve tends to leak, and if the water dribbles out of the exterior portion, the section through the wall freezes up in cold weather.
He's looking for a way to drop the level behind the high point by a couple of inches on cycle end so that a small leak in the valve won't dribble water into the external run. It's about a 50% duty cycle during the coldest weather, so it doesn't have to drop it much.
My thought was to put a check valve at the bottom of the 6" vertical section just inside of the wall. That check valve would draw air into that section just as the valve closes and the exterior vertical section empties creating a temporary suction. That check valve would have to draw air from outside, since if the drain does still freeze over or gets blocked for some reason, and the check valve fails under pressure, we don't want it spraying water inside. Plus he would want a long enough run that the air approaches room temp before it hits the check valve so that it doesn't freeze inside too.
My questions: Will it work? And will that 3' of vertical pipe produce enough vacuum to pull in sufficient air? My research tells me it will start at about .1mil, decreasing as it drains, but this isn't exactly my field. Thoughts?
