drainage problem

[rmack37]

I moved the washer from my kitchen to the other side of the house, about 15 ft away. I dug up the slab, and ran a new drain line. It hooks into the sewer line just outside the house. It has a good pitch and one 5 ft. section is quite steep as it runs under the foundation. I hooked up an elbow near the washer, but the water backed up. I then installed an automatic vent valve on the horizontal abs pipe after the elbow and before it heads down the drain. It drains fine with a hose, but backs up with the flow from the washer. I cannot figure out the problem, do I need another vent? Could the pipe be too steep?
Please Help
Rick

 

[TexMex]

A lot of what you say sounds rather strange, It could be due to different techniques in your country.

You say, that you dug up the slab and run the waste under the foundations. If you did that in this country, you would probably have put a whacking great hole through your Damp Proof Membrane, causing a major damp problem, in due course.

You say that you fitted an automatic air vent valve, but it is still backing up. How do you know? Automatic air vents should not allow the water out. You may also have fitted the wrong type of automatic vent. Some (used on waste water pipes) allow air into the system. Others, as used on central heating, let excess air out. If you've fitted the wrong type, it won't work. Alternatively, is it possible to fit these things the wrong way round?

Over here, I would use a fitting that includes a vent hole (no need for an automatic jobbie). But as I am in the UK, I am probably talking round things.