Air Admittance Valve Problem

[Mr La de da]

Hi Guys,

I need some advise on my situation. I have a downstairs cloakroom that has a soil pipe going directly to the underground sewer (man hole) not connected to the main vent pipe.

Basically I have fitted an AAV on top of the boss, but it is below the level of the basin that connects to the side of the boss. I found that when I flushed the toilet it would rise up and then very slowly go away.

So did some digging and fitted a silent trap to the basin (bottle trap) now problem is if I remove the purple plastic piece from the silent trap then the toilet will flush no problem, but if I fill the basin up water will flow out of the air valve when I pull the plug, if I place the purple plastic bit into the trap then the toilet doesn't flush right, I guess because of an vacum.

I have made a little drawing of how it is all installed, can someone help me with this situation?

Thanks

Mr L

 

[PlumbBobBob]

the air admittance valve is supposed to be higher than the highest water served unit (basin in this case) to alleviate just your situation.

steve

 

[Mr La de da]

Hi Steve,

Thanks for the reply.

Trouble I have is this is all fitted inside a vanity unit so it isn't really possible to get it above the basin. I was hoping that the silent trap fitted to the basin waste would sort this out, and it does to some degree if I remove the plastic seal on the basin silent trap.

The only other thing I could maybe do is fit something like a fexable pan connector to the top of the bass so that the AAV sits much higher, a straight pipe would be no good as there are a number of item in the way like pipes, cistern etc.

This would be just above the plug in the basin, would you think this is high enough?

Mr L

 

[WHPES]

You could put a dog-leg bend in the soil pipe to raise the AAV.

When you install a system like yours, you either do it the right way or the wrong way.

Pointless doing a bodge-up and then wondering why it doesn't work.

 

[tamz]

As WHPES said you will have to change it. You should really have thought it out before you started. The AAV must be fitted above the spillover level of the highest appliance.
When you remove the bit from the trap you are allowing air to enter and ease the vacuum.
Just a thought. Have you checked the durgo is working?

 

[Gray0689]

Can you not put a 35mm aav off trap at back of whb

 

[Bernie2]

Hmm!

Are you sure the problem is the AAV. An AAV only works if air is being drawn in to the drain, it simply lifts and lets air in to break the vacuum.

But it will not work if the problem is compression i.e air pushing back to the appliances from the drain an open vent does both.

Check to see when you remove the stopper whether the air is actually being sucked into the drain or it is blowing out of the drain.

If it is blowing out then you probably need the line venting somewhere.

Also you can check the distance above the main drain invert level by looking down the drain. The Building Regs give you distances when fitting AAV or stub stacks.

Good Fortune.

 

[Mr La de da]

Thanks for the replies guys, not looking to do a bodge up job, but as I am NOT a plumber I didn't know at the time I would have to fit the durgo above the highest spill level, if I did know I would have fitted it differently and wouldn't be asking for help on here.

I have noticed that this problem is also affecting the kitchen sink, slowly draining, if I completey remove the durgo in the cloakroom then it goes away fast, just lifting the rubber seal doesn't have the same affect. I assume that the kitchen sink and the cloakroom soil pipe are shared underground.

So I think my plan is to

A. Raise the hieght of the durgo to above sink level (maybe use a 32mm one because of space)

B. I am thinking about fitting another AAV in the kitchen also, I have enough space to fit a 32mm one.

Any problems with fitting two of these, gonna get down the plumbers merchants today.

Mr L

 

[Bernie2]

Hmm,

If you remove the Durgo and the water runs away a good guess is that the problem is compression or back pressure not vacuum.

Although you can move the Durgo above the spill over level, what have you achieved?

Only stopping water coming out the AAV before the basin if the line blocks. That does not seem to be your problem.

Check the drain line is clear and that you have a vent on the line. Also that you are using the Durgo in the right situation as the Building Regs say.

 

[Mr La de da]

Hi Bernie,

Thanks for the reply. Yes I moved the durgo higher up and achieved nothing like you say, I think that maybe the drain is somewhat blocked.

Today on the kitchen sink waste I fitted a small 32mm AAV just loosley in the pipe and it flew out when I turned the tap on, I then put it in more securley waited for the sink to fill right up i.e blocked, then removed the AAV and the air was sucked in and the sink emptied straight away.

I did the above a couple of times and now it runs clear all the time with the new AAV fitted like the problem has gone, I will buy a drain rod set and make sure they are clear, can you explain what you mean by a vent on the line?

The way the drain seems to run is from the cloackroom the soil pipe goes under the consevatory, joins into the kitchen sink pipe which then ends up in a manhole (i will confirm this when I lift the lamanite flooring to gain access to the manhole)

The upstairs bathroom seems all ok and this has a normal vent through the loft, but I know that the other end goes to the same manhole. One thing to mention is that before the extension was built the underground pipework was a little different, basically from the manhole the pipe split into 2, one leg went directly to the WC, and the other had like a drain gully on the outside, and the sink and washine machine went into this, you could pour water into this from the outside.

I think it may have been a gully-hopper

Catalogue - Marley Plumbing & Drainage

Would this be what you mean by venting the line? we actually removed the gully-hopper now, I was under the impression than the Durgo would take care of this instead?

Mr L

Here is a little sketch of how I think the drainage is laid out.

Mr L

 

[Mr La de da]

got the main drain cover up this morning, it was under the laminate floor in the conservatory, sure enough it was blocked and full of water, I got some rods and cleared it out.

All is good now and the Durgo is working fine.

Mr L