Underground waste drain pipe + cold water feed + hot water feed

FrankRizzo

Hi,

Any help appreciated with this.

I want to run underground, a waste drain pipe + cold water feed + hot water feed, for an outdoor sink/mini bath, for washing the dog after his big nature walks.

How do people do this for garden rooms, etc - do the pipes not freeze underground? What waste size would I run? What size for water pipes and is plastic ok?

Any help appreciated!

Thanks

grumbler

IIRK, it's at least 60cm deep for water pipes in UK, and I don't see why it can be less in your case.

For underground waste I don't think that anything smaller than 11cm (diameter) can be acceptable.

MikeJXE

grumbler said:

IIRK, it's at least 60cm deep for water pipes in UK, and I don't see why it can be less in your case.

For underground waste I don't think that anything smaller than 11cm (diameter) can be acceptable.

That was the case pre 1963, since them underground water pipes need to be 75cm deep minimum 

ThisIsWeird

Plastic is better, as it's (slightly) less likely to freeze in the first case, and it's more tolerant of being frozen should the worst happen. Ie, provided it doesn't have any (vulnerable) fittings along its length, there is every chance plastic will survive being frozen, whereas copper is quite likely to be permanently damaged by the expanding freezing water. In any case, running longish lengths of pipe is much easier done in 'plastic'.

I guess you have two choices - one is to bury the pipe deep enough to not be affected by frost, which is one reason why your incoming water main pipe should be at a min 750mm depth, and the other is to insulate the pipes well.

I would suggest a compromise should be possible - the 750mm rule applies to uninsulated pipe, so I can imagine a well-insulated pipe buried only ~1 foot or so would, in almost all situations, be fine. But that is pure assumption.

Frank, how deep can you go - or want to? Let's start from there, and then consider the options!

Options could include having thumb-isolating valves at the house end, so the pipes are depressurised after each use - the outdoor bath ends are left open. Pipes could even be run above ground in a box or trunking, provided they are well insulated, and the pipes actually used regularly - ie to keep the water temp inside them above freezing.

Or you could even add trace-heating wire, thermostatically controlled, so it always keeps the well-insulated pipes above freezing - this shouldn't cost much to run, as the actual pipes should rarely get close to 'zero', would take little to warm them up, and the amount of time when the temps are that cold is relatively little. 

For the waste pipe, the main criteria is that it 'runs' so doesn't hold water. Where will it drain to?

As to what size of pipe, that will depend on the type of supply you have in your house - mains-driven (unvented) or from a storage tank in the loft, and also the length of run. I'd hope that standard 15mm pipe would do, but it depends...

FreeBear

Don't forget, if you are hooking the waste up to an existing foul water drain, then Building Control should be notified - They will probably insist on 110mm pipe for the waste laid in a trench and covered in pea shingle. Possibly the same for any feed pipes.

FrankRizzo

ThisIsWeird said:

Plastic is better, as it's (slightly) less likely to freeze in the first case, and it's more tolerant of being frozen should the worst happen. Ie, provided it doesn't have any (vulnerable) fittings along its length, there is every chance plastic will survive being frozen, whereas copper is quite likely to be permanently damaged by the expanding freezing water. In any case, running longish lengths of pipe is much easier done in 'plastic'.

I guess you have two choices - one is to bury the pipe deep enough to not be affected by frost, which is one reason why your incoming water main pipe should be at a min 750mm depth, and the other is to insulate the pipes well.

I would suggest a compromise should be possible - the 750mm rule applies to uninsulated pipe, so I can imagine a well-insulated pipe buried only ~1 foot or so would, in almost all situations, be fine. But that is pure assumption.

Frank, how deep can you go - or want to? Let's start from there, and then consider the options!

Options could include having thumb-isolating valves at the house end, so the pipes are depressurised after each use - the outdoor bath ends are left open. Pipes could even be run above ground in a box or trunking, provided they are well insulated, and the pipes actually used regularly - ie to keep the water temp inside them above freezing.

Or you could even add trace-heating wire, thermostatically controlled, so it always keeps the well-insulated pipes above freezing - this shouldn't cost much to run, as the actual pipes should rarely get close to 'zero', would take little to warm them up, and the amount of time when the temps are that cold is relatively little. 

For the waste pipe, the main criteria is that it 'runs' so doesn't hold water. Where will it drain to?

As to what size of pipe, that will depend on the type of supply you have in your house - mains-driven (unvented) or from a storage tank in the loft, and also the length of run. I'd hope that standard 15mm pipe would do, but it depends...

Thanks for the detailed response!

Both hot and cold will run from the kitchen sink and thats where the mains water also enter the property. These pipes will need to run underground as boxing them above, won't work unfortunately due to the garden layout. It will run approx 5 meters - in terms of digging I would dig as deep as necessary albeit if I start hitting really hard stuff I may need to just aim for 750mm.

In terms of the waste, there is a rain water down pipe, I wonder if I can connect to that below ground? There is also a rodding point near by, not sure if I could connect to this? Also not sure if thats for rain water or foul waste - is there a way to tell?

FreeBear

FrankRizzo said: In terms of the waste, there is a rain water down pipe, I wonder if I can connect to that below ground? There is also a rodding point near by, not sure if I could connect to this? Also not sure if thats for rain water or foul waste - is there a way to tell?

You would need to lift a manhole cover for the foul water drain and see if there is any water flowing when you dump a bucket full down the rodding eye. Do the same for the downpipe if there is easy access to the gutter.

Hopefully, the downpipe will go off to a soakaway within the property boundary - If it does, check your water bill and make sure you are not paying extra for the privilege.

Waste water from washing shouldn't be going into a soakaway as there is potential for soaps to contaminate the ground water.

Section62

FrankRizzo said:

Both hot and cold will run from the kitchen sink and thats where the mains water also enter the property. These pipes will need to run underground as boxing them above, won't work unfortunately due to the garden layout. It will run approx 5 meters....

Running hot water out to an external sink isn't a great idea.  It will take a while to get hot water coming out of the tap, and each time you use it there will be a relatively large volume of hot water wasted.  The biggest problem with the pipes is not going to be where they are buried, but where they come up above ground to the sink - even if you lag the pipes, the taps may still freeze solid.  You will need to use a fair amount of ingenuity to protect the pipes (and sink waste trap) from frost, without making the sink too much hassle to use each time.

Also, if you get building control involved in the drainage (which I agree with FreeBear you should) then I would expect them to comment adversely on the idea of taking a hot water supply out of the house to the sink.

You could probably save yourself some waste if you used a mixer valve inside the house to provide water at a fixed temperature through one pipe, albeit at the expense of not having a cold (only) supply as well.  I still think this could be a breach of building regs though.

I think in the same position I'd probably just use a hose pipe to get water to the dog washing place - disconnecting that and putting it in a frost-free place when not in use.  It would be less convenient than a permanent arrangement, but probably marginally so by the time you have sufficiently protected permanent pipes/taps from frost.

Connect the hose to an outside tap supplied by a blending valve and you can arrange to have the water at a dog-friendly temperature whatever time of year.

Whatever you do, make sure the supplies going outside are protected by double check valves.  If something goes wrong you won't want any of the 'outside' water being drawn back into the house plumbing.

ThisIsWeird

FrankRizzo said:

Both hot and cold will run from the kitchen sink and thats where the mains water also enter the property. These pipes will need to run underground as boxing them above, won't work unfortunately due to the garden layout. It will run approx 5 meters - in terms of digging I would dig as deep as necessary albeit if I start hitting really hard stuff I may need to just aim for 750mm.

In terms of the waste, there is a rain water down pipe, I wonder if I can connect to that below ground? There is also a rodding point near by, not sure if I could connect to this? Also not sure if thats for rain water or foul waste - is there a way to tell?

You certainly shouldn't have to go anywhere close to 750mm deep to avoid freezing (measure that out - it's pretty deep!).

I would certainly fit easy-to-use thumb-shift isolators at the kitchen end, ideally before the pipes exit the house.

Your kitchen 'cold' will be mains-driven, but that's not to say the hot will be. Do you have a combi boiler? If it is, then 15mm pipes will be fine for both.

Also, since the cold is coming directly from the mains, there should be a check-valve (one-way) to prevent any contaminated water going back up the wrong way from your dawg in the event of a mains water failure. This can be fitted just after the isolator, or you can even get them built-in.

If you open the rodding point, you should be able to tell what it's for - drain a sink or basin in the house, or flush a loo! If your rainwater downpipes are separate - some are, some are not - then it'll likely be leading to a soakaway rather than the sewer. Tbh, for all you will be using this for, I 'think' either is fine. I would, tho', run your new drain via a 'gulley' - a U-bend - to catch any sediment and stuff. Or, if the sink is close to where the D/P goes into the ground, just point it in there...

Section62

FreeBear said:

Waste water from washing shouldn't be going into a soakaway as there is potential for soaps to contaminate the ground water.

I agree, also for the reason that if the dog gets muddy enough to need washing outside, the soil from the wash water will soon start clogging up a SW soakaway.

For the same reason the drainage to the foul sewer should have some form of catchpit arrangement to allow suspended silt/soil to settle out in a controlled location, rather than in any low spots in the foul drains.

FreeBear

Section62 said: Whatever you do, make sure the supplies going outside are protected by double check valves.  If something goes wrong you won't want any of the 'outside' water being drawn back into the house plumbing.

And also fit easily accessible stopcocks inside so that when the pipes do freeze, you can isolate the water.