Washing machine waste plumbing

[staffordian]

I've been meaning to get opinions on this for a while.

Our kitchen has a vertical pipe into which the waste water hose of the washing machine feeds. This joins the pipe taking waste water from the kitchen sink.

What I'm not sure about is the fact that the washing machine pipe runs straight into the sink waste via what I think is called a swept tee; in other words it "aims" the water in the right direction along the sink waste. But, and here is where I worry, there is no trap, so surely any smells in the sink waste can simply vent into the kitchen via this washing machine pipe.

There is no direct conection to the sewers; the pipe terminates outside over a gully so there is no issue of sewer gases coming in, just any smell from the inevitable gunge in the kitchen waste pipe.

I've Googled this arrangement and found conflicting opinions, but we do get some bad smells in the kitchen, which my wife thinks is from the sink waste or overflow, but which I feel can't be helped by the washing machine waste pipe being arranged as it is.

A secondary question is whether it would be possible to fit a trap.

I'm thinking in terms of an S trap. Cutting the existing vertical pipe near its base, adding an S trap and fitting the cut off pipe to the S trap.

Does this sound a reasonable course of action, and if so, are there any gotchas I need to be aware of?

TIA

Staffordian

[richlist]

Are you actually getting unwanted smells out of the washing machine pipe ? If not leave it alone.

[staffordian]

Are you actually getting unwanted smells out of the washing machine pipe ? If not leave it alone.

Good question...

The washing machine is a bit tricky to move in and out so I've not actually had my nose against the pipe. We definitely get slight "bad drain" smells in the kitchen from time to time, and I don't see where else it can be coming from. To my rather poor sense of smell, it doesn't seem to be coming from the sink. Putting bleach down the sink helps, but it would presumably help kill smells in the pipe and stop the smells wherever they were escaping.

[jfgw]

The pipe itself could be a bit gunged up and smelly. A gentle breeze in the right direction could send these smells into the kitchen. If there is room, you could temporarily fit a small bowl or jar under the pipe outside and fill it with water to make a trap. If the smell goes away, either fit a proper stand-pipe or plumb the washing-machine into the sink trap. You may have to replace the sink trap with one with a spigot if you do the latter.

A regular maintenance wash is good for cleaning the washing-machine and will also help clean the waste. Place a handful of soda crystals into the drum (not caustic soda - that will eat the aluminium) and run the machine on the hottest wash, usually a 90° or 95° cotton wash. Once per month is usually recommended. The temperature that modern detergents work at is not enough to kill bacteria and mould so washing-machines get mankier inside now than they used to.


Julian F. G. W.

[Lootman]

The pipe itself could be a bit gunged up and smelly.

A regular maintenance wash is good for cleaning the washing-machine and will also help clean the waste. Place a handful of soda crystals into the drum (not caustic soda - that will eat the aluminium) and run the machine on the hottest wash, usually a 90° or 95° cotton wash. Once per month is usually recommended. The temperature that modern detergents work at is not enough to kill bacteria and mould so washing-machines get mankier inside now than they used to.

Interesting. There is a bad smell emanating from behind our washing machine. My first thought was a dead animal rotting there but that was not the case. It is in an outhouse with 2 doors between it and our kitchen, and very well ventilated, so I don't worry about it too much.

But the thing is, my wife insists on washing everything with a cold wash. So hot water never goes through the system. Could be the problem if you're right about that.

[staffordian]

The pipe itself could be a bit gunged up and smelly. A gentle breeze in the right direction could send these smells into the kitchen. If there is room, you could temporarily fit a small bowl or jar under the pipe outside and fill it with water to make a trap. If the smell goes away, either fit a proper stand-pipe or plumb the washing-machine into the sink trap. You may have to replace the sink trap with one with a spigot if you do the latter.

A regular maintenance wash is good for cleaning the washing-machine and will also help clean the waste. Place a handful of soda crystals into the drum (not caustic soda - that will eat the aluminium) and run the machine on the hottest wash, usually a 90° or 95° cotton wash. Once per month is usually recommended. The temperature that modern detergents work at is not enough to kill bacteria and mould so washing-machines get mankier inside now than they used to.


Julian F. G. W.

Some good suggestions there. Thank you.

I may be able to try a temporary trap outside. It would be very Heath Robinson, with string or wire to hold something in place, but worth a try.

We do have a spare spigot under the sink, so could cut a hole in the side of the cupboard and route the waste that way. Is there a proper fitment to cap off the then unused standpipe, or is it just a case of finding something the right size and bunging it on with some sealant?

I must admit this option is one I considered a while ago but then read somewhere that a standpipe was the preferred method. Can't really see what difference it makes myself though.

Agree about ensuring that the washing machine is clean. I did a two hour sixty degree clean out with a cleaning solution today, but we only do it infrequently. I must do it more often. I've read that not only do low temperature washes lead to build up of bacteria etc, but that liquid pods (which we now use) are worse in this respect than powder. So a double whammy.

Thanks again,

Staffordian

[Mike4]

I've been meaning to get opinions on this for a while.

Our kitchen has a vertical pipe into which the waste water hose of the washing machine feeds. This joins the pipe taking waste water from the kitchen sink.

What I'm not sure about is the fact that the washing machine pipe runs straight into the sink waste via what I think is called a swept tee; in other words it "aims" the water in the right direction along the sink waste. But, and here is where I worry, there is no trap, so surely any smells in the sink waste can simply vent into the kitchen via this washing machine pipe.

There is no direct conection to the sewers; the pipe terminates outside over a gully so there is no issue of sewer gases coming in, just any smell from the inevitable gunge in the kitchen waste pipe.

The original installer is the architect of a right ol' bodge (technical term). There should ALWAYS be a trap at the base of an open-ended standpipe and a complete kit is the normal way of doing this. E.g.


https://www.bes.co.uk/washing-machine-t ... 0mm-10503/

But if you don't have room to fit one, you could a cap off the top of your existing open-ended standpipe (using a coupling and a rodding eye) then use a 'Self-Cutting Washing Machine Waste" to connect your washing machine waste hose directly to the side of the existing upstand.


https://www.bes.co.uk/single-self-cutti ... aste-6957/

[88V8]

As Mike has illustrated, there should always be a trap.

The conventional solution if there is a sink in the offing, is this
https://www.ebay.co.uk/itm/1-1-2-To-40m ... SwhhJfJSfY a sink trap which incorporates a side spigot for the washing machine hose.

V8

[Dod101]

Of course there should be a trap but I second the idea of cleaning washing machines and dish washers with a very hot wash and a proprietary cleaner every coupled of months or so. The same goes for hot water coming out of the hot water tap. Legionnaire's disease can be the result if you do not. The current trend towards 'economy ' washes and so on is not good for our health.

Surely Lootman's wife, or at least her washing machine, is not actually washing clothes in cold water?

Dod

[swill453]

Of course there should be a trap but I second the idea of cleaning washing machines and dish washers with a very hot wash and a proprietary cleaner every coupled of months or so. The same goes for hot water coming out of the hot water tap. Legionnaire's disease can be the result if you do not. The current trend towards 'economy ' washes and so on is not good for our health.

I'd imagine 95%+ of people don't bother with regular very hot cleaning cycles in their washing machines and dishwashers, but I've never heard of anyone catching Legionnaire's disease as a result. Have you?

Scott.

[Dod101]

Legionnaire's disease can come from not using hot enough water in your hot water heating system not from dish or clothes washers. I thought and think that is what I said in my post.

Dod

[swill453]

Legionnaire's disease can come from not using hot enough water in your hot water heating system not from dish or clothes washers. I thought and think that is what I said in my post.

A bit of a red herring then, as these devices pretty much exclusively have cold feeds only. No health risk there that I'm aware of.

Scott.

[jfgw]

Since there is already a spigot under the sink, using this would probably be the simplest way of rectifying the situation. This is the most common method but stand pipes are also very common. The hose must loop upwards to prevent sink water from entering the machine - see the second from last diagram here, https://www.diydata.com/plumbing/washin ... achine.php . Some sink traps with spigots have a simple one-way flap valve but it is best not to rely upon this.

Another (non-standard) method I have seen is to have the hose go through a hole in the wall. In one case, this was near floor level so that, if the hose wasn't held with an upward loop, the machine would continuously empty itself while it was being filled.

There are two main types of plastic waste pipe commonly in use: push-fit and solvent weld. They are not compatible. A compression blanking cap will fit either: https://www.screwfix.com/p/mcalpine-t23 ... 40mm/96079 , but may not fit easily if the pipe is close to the wall. If the pipe is push-fit, you can probably remove the existing stand pipe and fit a blanking plug, https://www.screwfix.com/p/floplast-pus ... 40mm/34151 . Alternatively, fit it to the top of the stand pipe using a straight coupler, https://www.screwfix.com/p/floplast-pus ... 40mm/17406 . For solvent weld pipe, do as Mike4 suggested and fit a rodding eye using a straight coupler, https://www.screwfix.com/p/floplast-abs ... pack/23322 & https://www.screwfix.com/p/floplast-str ... pack/58998 .

Use a proprietary washing-machine cleaner if you wish, or buy a packet of soda crystals for a fraction of the price (which will do quite a few cleans). I have also been told to use washing powder but this was by a rep from Procter and Gamble. Soda crystals are cheaper.


Julian F. G. W.

[jfgw]

Legionnaire's disease can come from not using hot enough water in your hot water heating system not from dish or clothes washers. I thought and think that is what I said in my post.

A bit of a red herring then, as these devices pretty much exclusively have cold feeds only. No health risk there that I'm aware of.

Scott.

I don't know of anyone personally who has had Legionnaire's disease (AFAIK, the person I know of who keeps his stainless hot water cylinder set to 40°C is still alive). All sorts of things can grow in a washing-machine, however, unless it is killed off. Have a look in the door seal - they are often mouldy.


Julian F. G. W.

[Dod101]

Legionnaire's disease can come from not using hot enough water in your hot water heating system not from dish or clothes washers. I thought and think that is what I said in my post.

A bit of a red herring then, as these devices pretty much exclusively have cold feeds only. No health risk there that I'm aware of.

Scott.

Oh well, that's good.

Dod

[Mike4]

Legionella as I understand it, only grows in standing water which is between tepid and hand-hot. Raising and keeping the water temp at about 55C kills it.

55C is uncomfortably hot to human skin though, which is why the hot tap water in public institutions always seems stupidly hot. It has to be for legionella safety.

[staffordian]

Job done. Thanks all especially Mike and Julian.

When I got the washing machine out, it was worse than I thought. The standpipe was only 12" long, which I'm sure isn't enough, and was sited behind the adjacent cupboard to the right, which had a cut out on the side to accomodate it. There was evidence that the pipe had overflowed a little.

I used the spigot on the sink, which is just to the left of the washing machine, and the waste pipe enters towards the top of the unit and falls to the spigot, so run back shouldn't be an issue.

With a bit of judicious cutting away of the side of the right hand cupboard I managed to fit one of the McAlpine blanking caps to the standpipe, so all should now be pong free.

The only side effect of the change is gurgling when the washing machine pump starts and stops. A small price to pay.

Staffordian

[jfgw]

The only side effect of the change is gurgling when the washing machine pump starts and stops. A small price to pay.

It might be worth putting some cleaner down the sink. Caustic soda shifts the slimy stuff but not limescale. Don goggles and gloves and dissolve as much as you can in some water first. My favourite (sulphuric acid such as One Shot) is now trade only unless you have a licence. Spirits of salts (hydrochloric acid) is still freely available from proper independant hardware shops but it is not as strong.

Julian F. G. W.

[staffordian]

The only side effect of the change is gurgling when the washing machine pump starts and stops. A small price to pay.

It might be worth putting some cleaner down the sink. Caustic soda shifts the slimy stuff but not limescale. Don goggles and gloves and dissolve as much as you can in some water first. My favourite (sulphuric acid such as One Shot) is now trade only unless you have a licence. Spirits of salts (hydrochloric acid) is still freely available from proper independant hardware shops but it is not as strong.

Julian F. G. W.

Thanks, yes, next job, I think. We've been intending to do it for ages as it doesn't seem to drain as quickly as it used to, so it probably has a bit of gunk in it.

Staffordian

[richlist]

A word of caution.
Most washing machines specify the minimum and maximum height of the highest part of the waste hose. Make sure your waste hose is within these limits.