Kitchen without plumbing roof vent - can I put in a dishwasher?

[getsorted]

I purchased an 801-square foot cinderblock house built in 1947, and the kitchen drain is always slow. It doesn't vent through the roof, I guess because the wall is cinderblock, or because it wasn't required at the time. I got some improvement in drainage by replacing the air intake valve under the sink, but it remains slow. Snaking and chemical drain openers didn't seem to make a difference.

I had been using a portable dishwasher that drained into the sink basin, but one day, the drain completely backed up and the sinks overflowed.

My question, is, is the drain just slow because it isn't vented to the roof? Do air intake valves just not allow for the capacity a dishwasher needs?

This is particularly important to me because I also want to add a washing machine to the house (it currently has no drain or hookups for one), and the plumber suggested running a drain line to the main kitchen drain line. I don't want more backups.

The main line is clear and the bathroom, on the other side of the house, does have its own roof vents, and everything drains well there.

[uniwelder]

This does remind me of my former house--- built in 1950, 750 sq ft, concrete block construction, and no drain vents.  When lots of water went down the kitchen sink, the plumbing trap of the bathroom would gurgle.  There was no dishwasher, though there was a washing machine in the basement, but I never had any problems getting water to drain.

I would guess an air valve should allow sufficient flow for proper drainage, so I'm taking an uneducated guess that the line is clogged up.  Stupid idea--- have you looked at the slope of the pipe?  Sometimes they run uphill to drain and will catch lots of clog inducing sediment/grease.  Are your drain lines pvc or steel or cast iron?  Changing it to plastic if steel or cast iron might be a relatively easy fix, even without the proper venting.

[BudgetSlasher]

When you say air intake valve you mean something like this (https://www.homedepot.com/p/Oatey-Sure-Vent-1-1-2-in-x-2-in-PVC-Air-Admittance-Valve-with-160-DFU-Branch-and-24-DFU-Stack-39016/100201861) correct?

My dishwasher and kitchen sink are on one of those and I have no problems. That should handle all of your needs. In the title (a more specific numbers in the specification document) you will see DFU (drain fixture units) that the device can handled on a branch and on a stack. Your unit should have a similar rating.

The product I posted has this with it (https://images.thdstatic.com/catalog/pdfImages/a6/a6d71e67-d253-4f02-8e57-95da7246e47e.pdf) Based on that a washing machine is 3 DFU, sink and disposal is 2, and a dishwasher is 2. If that is all that is vented through your valve that is a total of 7 ... well below any of the limits I saw for such a device.

I suspect your problem is somewhere in your drain system. I think your house predates wide spread use of PVC in North America, so you might have cast iron. Those have their own special way of corroding from the inside and building up hard deposits that your regular homeowner grade snake isn't going to do much about. If you do have metal drain lines someone might be able to chime in on the best way to reopen them. But Master Plumber Google says cast iron or galvanized drain lines that were installed 75 years ago could be reaching end of life.

[chemistk]

I would tend to agree with BudgetSlasher - I have a friend who had to replace all the cast iron drains in his 1950's house a couple months ago because of both pinhole leaks and because of interior deposits that couldn't be addressed.

It might be worth it to get a plumber to come out and scope your drain lines to see if there is something blocking things and/or to verify the state of the pipes.

[getsorted]

When you say air intake valve you mean something like this (https://www.homedepot.com/p/Oatey-Sure-Vent-1-1-2-in-x-2-in-PVC-Air-Admittance-Valve-with-160-DFU-Branch-and-24-DFU-Stack-39016/100201861) correct?

Similar, but cheaper: https://www.lowes.com/pd/Keeney-Plastic-Air-Admittance-Valve/1069119

Everything I can see is PVC; however, getting under the house is impossible-- the crawlspace is only about 11 inches and I... am more than that.

End of life on cast iron pipes would make sense. There is a breaker in the breaker box marked "washer-- not used," but I can't find any place in the house where there are or would have been either a drain line or water hookups. I will know more once I remove all the carpeting. There is a mystery pipe coming out of the roof on on side of the house that might be a vent, but it isn't near anything currently plumbed in.

That said, the clean out and bathroom drains are PVC. I had the main line snaked with a camera last year. They did mention there appeared to be another drain line coming from somewhere that wasn't used. I need to find a way to get a better picture of what's under there.

Thanks very much, everyone, for your advice.

[BudgetSlasher]

When you say air intake valve you mean something like this (https://www.homedepot.com/p/Oatey-Sure-Vent-1-1-2-in-x-2-in-PVC-Air-Admittance-Valve-with-160-DFU-Branch-and-24-DFU-Stack-39016/100201861) correct?

Similar, but cheaper: https://www.lowes.com/pd/Keeney-Plastic-Air-Admittance-Valve/1069119

Everything I can see is PVC; however, getting under the house is impossible-- the crawlspace is only about 11 inches and I... am more than that.

End of life on cast iron pipes would make sense. There is a breaker in the breaker box marked "washer-- not used," but I can't find any place in the house where there are or would have been either a drain line or water hookups. I will know more once I remove all the carpeting. There is a mystery pipe coming out of the roof on on side of the house that might be a vent, but it isn't near anything currently plumbed in.

That said, the clean out and bathroom drains are PVC. I had the main line snaked with a camera last year. They did mention there appeared to be another drain line coming from somewhere that wasn't used. I need to find a way to get a better picture of what's under there.

Thanks very much, everyone, for your advice.

That looks like it would be enough for what you are talking about. I did not see a rating for it, but your load is pretty small so it should be fine. A quick thought, is it installed in the correct place (on the house, not sink, side of the drain trap and high enough that water doesn't back into it)? I suppose you could test that it is not the valve by removing it and running everything. The open pipe should let enough air in, so if it still is slow to drain (or backs up out the opening ... might want to put something underneath just in case) you know the problem is elsewhere.

At your house's age it is also entirely possible that it has been replumbed or it could also be that PVC has been tied to older pipes when remodels have been done. Someone will have to look.

[getsorted]

A quick thought, is it installed in the correct place (on the house, not sink, side of the drain trap and high enough that water doesn't back into it)?

It is installed in the right place; at least, it's as high as it can go and still be inside the cabinet. When the sink overflowed, I removed it and water came out the top of the pipe for a second, but it doesn't normally.

I am betting that the drains for the bathroom were redone when the bathroom was remodeled in 1994, but the kitchen (on the other side of the house) wasn't. The guy who owned it before me was a bachelor and may have just decided it was easier to use the laundromat down the block than replace the washing machine drain when it failed. That would explain the "washer - not used" breaker.

My ultimate plan is to add a second bathroom near the kitchen anyway, so I may end up redoing the kitchen drain and adding a new washing machine drain as part of that project.

The plumber said the only way to really see was to pull up some of the flooring. I think my only other option is an RC car with a camera to go under the house! Even my skinny inspector couldn't get more than half his body in.