5 Mobile Home Plumbing Ventilation Problems Solved


Today, we are continuing our Ask a Mobile Home Expert Series. We get a lot of questions related to mobile home plumbing ventilation problems so we’re tackling a few more this week. These questions are in the comment section of our two extremely popular articles about mobile home plumbing: 

Manufactured Home Plumbing: Drainage and Ventilation Issues

Plumbing In Manufactured Homes: The Basics


Mobile Home Plumbing Ventilation Problems are Very Common

Mobile home plumbing ventilation problems are common in mobile homes. Most homeowners know about their home’s water supply lines and drainage lines but they aren’t very familiar with their plumbing’s venting system. The majority of questions that we get from readers usually involves either a stoppage or a venting problem.


 Mobile Home Plumbing Ventilation Problems

The following mobile home plumbing ventilation questions are from real readers and have been answered by a friendly and experienced licensed master plumber.

Read our first Ask a Mobile Home Expert article about venting issues and sewer smells here.


Thumping in the Walls, Slow Drains and Bubbling Toilets 

I live in a 2008 manufactured home and hear thumping in the walls, slow drainage in the sinks, and bubbling in the toilet when the washer drains.

Am I having a ventilation issue? What am I looking for when I go up on the roof to check the stack?

Also on the back of my home is an odd spigot, it has a seal on top and it will not turn on? I think it might be pressurized? Is it necessary or can I replace it?

This is more than one issue so we recommend you call a plumber but we’ll get you pointed in the right direction so you save time and money and can get everything fixed in one call.

The thumping is likely from your water lines not being strapped properly- it happens a lot. There is a product called hammer arresters that will help but a plumber will probably need to install it. This Family Handyman article can explain more. 

The slow drain sinks are probably hair build up but could maybe be linked to a vent issue at the washer drain. Make sure there is nothing blocking or partially blocking the drainage lines. Click here to learn more about unclogging a drain. Snake out each point that you are experiencing issues.

I would also check the washer drain pipe. If it is too small it can’t get the proper air flow. New washers are especially powerful so make sure to have the right size drain line that the manufacturer recommends. A quarter inch can make all the difference.

If that doesn’t fix it then check the ventilation lines. You definitely need to call a plumber before the issues become serious problems.

The seal on top of the spigot that you mention at the end is probably a vacuum breaker and they are pretty important. A plumber can give you a definite answer.


hammer arrester for banging plumbing lines - mobile home plumbing ventilation problems
Read more about a hammer arrester at family Handyman (image source).



Toilet Backflows into Bathtub when Flushed

When I flush my son’s toilet it backs up into the bathtub. The only way I could get it to drain was to open the main pipeline? Is there a ventilation issue?

It’s more likely to be a stoppage in the waste line than a ventilation problem. If you aren’t dealing with noise, smell, or other issues it’s probably just a stoppage.

Mobile home plumbing ventilation problems probably wouldn’t affect it that way. If it would have been a vent issue the toilet flushing would only have sucked the water out the tub trap.

Read our mobile home bathroom guide here to learn the difference in sizes from mobile home bathtubs and site-built home tubs. 



Water Backflows into Shower and Tub

We bought our 1993 16X80 manufactured home about 8 years ago and county code requires a treatment plant and septic tank that is pumped out to 3 sprinklers behind the house. My problem started about a year ago with water backing up into the master bathrooms sink, tub and shower drain. And the toilet wouldn’t flush.

I called a friend who helped install the main line under the house and he snaked it and everything was fine. Then we installed new toilets in both bathrooms and the master bathroom started gurgling and water rising up into tub and shower. I’ve checked the stack vents and sink vent(AAV). To no avail…please help. Any pointers will be appreciated!

This could be a couple different things. If it is ventilation try adding an additional vent for the master bath sink, tub, and toilet (tie them together on a single waste line).

If it’s a grade issue on the waste line you’ll want to get the T-branched and graded properly. You need 1/8″ of grade for every foot of pipe (if it is 3″ or 4″ pipe). Also. make sure it doesn’t have any dips in it. You’ll want to strap or hang it every 4ft, if possible, or build a stand every 4ft to keep a steady percentage of fall to the sewer tap.

ask a mobile home expert - mobile home plumbing ventilation problems -


What’s That Smell?

I smell a foul odor on the drainage since last week. However, it is not clogged but it really smells bad?

If it’s coming from the drainage/waste line you probably just need to snake it out really well. A blockage is in there somewhere.


plumbing snake - mobile home plumbing ventilation problems - ask a mobile home expert series
This snake is available at Amazon for $32.95 (affiliate link).



Stagnate Water in a Rarely Used Bathroom

I’m in a bath and a half single wide. Had an issue with smelly hot water a year or so ago, flushed the water heater and that took care of it.

The main bath and kitchen water is fine. The half bath, the hot water stinks. That room isn’t used as much, it clears if you let the hot water run (takes a while to get hot since it is at the far end of the home).

I suspect it’s from the water sitting in the supply line. Is there anything I can do short of replacing that supply line?

It sounds like the water is just stagnating in the line since it isn’t getting used much in that room. I don’t think new lines will help in this situation – it’s likely the water more than the pipe.

You may be able to solve the issue with a re-circulating system (affiliate link). A pump with a built-in timer is installed on your water heater. It opens the loop when the hot water in your line cools and recirculates into the heater to reheat. It would keep the water fresher and likely take care of that smell for you.

Recirculating systems are popular because they help save water by having hot water ready to go when you need it. Tankless water heater systems could also be helpful to you.


water heater recirculation system - mobile home plumbing ventilation problems - ask a mobile home expert
A recirculation pump sits atop a water heater. This one is available at Amazon for $188.76 and is fairly easy to install. (Affiliate Link)



Hope there questions and answers can help you with your mobile home plumbing ventilation problems. Next week on our Ask a Mobile Home Expert Series we will tackle manufactured home additions.

Thank you for reading Mobile Home Living!

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