Dishwasher installation - 3.5 metres from water inlet / waste outlet

[TerminatorUK]

Hi folks,

I hope you are all well.

Please go easy on me - I am an amateur DIY'er and this is about my first planned out plumbing job!

With that out of the way, I hope I have done my research correctly but before I start to lift a drill, I would really appreciate it if I could get my 'homework checked' to ensure I'm not doing something crazy / dangerous before I start:

The problem / task

• I wish to install a new dishwasher I have purchased
  
• There is no 'logical' position (unlike the washing machine's current location to the left of the sink) to place the dishwasher without a major re-work of the kitchen units
• I'll be 100% honest and admit I lack the skill, willpower or funds to have the kitchen altered to allow a better placement of the machine unfortunately

Annotated photo and my work diagram (forgive my awful drawing)

Proposed Solution

For the water inlet

• I have purchased a 3.5m x 15mm standard washing machine flex hose. This will be clamped with 15mm clips at the kick-board level at the rear of units / cooker. As I understand, the pressure in the hose means that positioning isn't vital (as long as there at no kinks in the hose). It is being place at the bottom of the units to avoid heat from the oven.
• There is no spare 3/4" 'Appliance connector tap' (sorry for the terminology), however, I have read about (and now purchased) a 15mm water pipe self-tapping appliance tap which I intend to install on the cold water feed which runs to the sink

For the waste outlet

• As I understand (unlike the water inlet hose) the placement of waste pipe needs a lot more consideration.
  
• The pipe needs to be initially raised near the machine (in the manual, the maximum head height is 800mm) and then gravity does the rest of the work
• There is nothing stated in the manual specifically about maximum drain hose length but most sources I have read say around 10-12' is about the maximum which I know I'm pushing and therefore a little concerned about
  
• Reading around (although I realise it is not ideal) I have read there is no regulations or restrictions from running piping behind a cooker. I have, however, read that potential waste heat from the cooker might be cause for concern
• To this end, I have acquired an unwanted piece of 22mm Copper pipe from a family member that is 915mm long - enough to clear the rear of the cooker by approximately 20cm each end (when placed on a diagonally downwards-facing slope going towards the drain under the sink)
• The copper pipe will have an ECL14 Earth Clamp for bonding installed to another copper pipe with 10mm2 core Earth Cable 6491x (this is more belt and braces - I read this is more of a requirement in special rule areas like bathrooms and kitchens don't apply but didn't want to take any chances)
• The 1500mm x 22mm waste pipe pre-installed into the dishwasher will be directly placed over the 22mm copper pipe and a jubilee clip applied (I'm not sure if I require PTFE tape or Plumber's Mait on the end of the pipe to make it extra secure - I realise it isn't threaded but I don't know if this will help the seal?)
  
• I was initially looking at extending the piping using 22mm Plastic Overflow piping but this would have involved x2 push-fit joints which I read on Saniflo's "10 golden rules" not to do for waste pipe connections (and also not to use 90 degree elbow joints)
• Instead, I have decided to another 1500mm leg of flexible waste hose coming from the other end of the copper pipe (this will be frequently hose clipped to the wall to help its rigidity)
• Finally, this will be terminated with a new bottle trap (which I know isn't recommended for kitchen sinks but I wanted to replace like-for-like as we have had no problems and there is limited space under the sink) which has 22mm / 18mm appliance waste hose inlet

My Concerns / Thoughts

• I'm concerned with the total length of the drain hose. I hope the rigid piece of copper and the angle (for gravity) will mitigate this concern but am I on a collision course for trouble?
• I know waste pipes are meant to be 40mm, however, I assume that is more for gravity-only fed wastes (like basins). As the waste hose from the dishwasher is already 22mm, I assume it is 'safe' for the connecting copper pipe to also be 22mm (I would guess that the dishwasher's pump provides the pressure required to push the waste water sufficiently down the smaller diameter of pipe)?
  
• The waste 22mm rubber ends are currently going 'naked' (albeit with a tight fit) onto the ends of the copper pipe. Am I missing something obvious (like a connector) that would mitigate any waste heat conducted along the pipe that might 'melt' the rubber connections (I am thinking the rear of the cooker wouldn't get hot enough for this to be a cause for concern)?
• Are 15mm self-tapping appliance taps fairly routine / 'safe' to use? Is the sink's cold water inlet a good 'target' for positioning the tap installation or is there a better spot I could choose?

Many thanks for any thoughts / advise / warnings you can give me in advance - it is very much appreciated!

 

[chappers]

As you suggest the water is pumped by the dishwasher, just extend the waste hose as necessary. . Ours pumps further than yours and just lays along the floor under the units with the joints jubilee clipped around a double spigot. The reason it is raised is to prevent accidental siphoning, ours doesn't rise up until it reaches the spigot at the trap and hasn't leaked in 10 years. and is also connected to a self cutting appliance tap. Just to say the route looks more like less than 2.5 metres

 

[TerminatorUK]

Thanks for your reply Chappers - gives me some confidence that someone has attempted something similar to this before

 

[just pumps]

All I will add is keep the discharge pipe as high as possible for as long as possible, and no dips & rises. Shouldn`t need PTFE tape or plumbers mait as the discharge pressure is minimal. At the end of the day create a water slide and you will be ok.

 

[Steve]

I had a similar setup, just ran an extended drain hose along the floor then up to a spigot under the sink. It worked fine. The pump in the dw is designed to pump upwards a couple of feet. If this occurs after a couple meters of horizontal route it wont have any significant effect on is performance. Most dws will also contain a backflow device.

 

[Steve]

Your oven wont actually get that hot. It'll probably be cooler than the water running through your drain hose.

 

[just pumps]

I had a similar setup, just ran an extended drain hose along the floor then up to a spigot under the sink. It worked fine. The pump in the dw is designed to pump upwards a couple of feet. If this occurs after a couple meters of horizontal route it wont have any significant effect on is performance. Most dws will also contain a backflow device.

Thinking you got lucky with all the new water pushing the old water in the looong U bend up not really what the R&D team had in mind I would say.

 

[chappers]

this setup has worked fine on ours for over 10 years on 2 different cheapo dishwashers....5h1t shouldn't have said that should I?

 

[just pumps]

Time will tell mate. lol

 

[TerminatorUK]

Your oven wont actually get that hot. It'll probably be cooler than the water running through your drain hose.

Thanks for the responses guys - it is very much appreciated.

I didn't realise it wouldn't get too hot - I suppose I could have used a length of plastic tubing instead then (or again, would copper have been a better choice still?).

The diagram is poorly drawn but yes - it will be installed as a 'slide' (it won't raise or go level at any point) - the highpoint being near the dishwasher and the low point is at the sink / drain.

I'll be doing the installation this weekend so I will report back on the results!

 

[TerminatorUK]

Hi folks - as promised here is my report back from the work I undertook on the bank holiday weekend.

Everything nearly went according to plan except for I have to re-route through one of the cabinets as it was impossible to access the one I wanted to go to in the corner between the sink and the oven.

However, other than this, I'm happy to report the job was a complete success and the dishwasher is working brilliantly - here is some photos of my work to illustrate the work as it progressed:

Original bottle trap...

New bottle trap with appliance fitting and new tap on the copper pipe (was worried when it initially sprayed a bit whilst screwing in). Wasn't happy with pipework below the trap (was too pressurised with bigger bottle trap and went 'up' a bit)...

With modified piping below and waste hose connection (not yet attached to clips on the wall at this point). Decided to use LS-X as sealant (LOVE that stuff - so much better than PTFE or Plumbers Wait) on all the fixings...

22mm copper pipe behind the removed integrated oven. Earthing clamp installed but wire not attached yet...

Photo up the back of the oven showing gap between oven and wall. No happy with earthing clamp position - hard to tell but I think it was touching the metal case - decided to take oven out and re-do the clamp...

Modified the earthing clamp - much happier now. There is a distinct gap between the pipe and the rear of the oven now...

My first attempt at using a hole saw (on the left of the actual hole) to create the initial entrance from the dishwasher drain to the copper pipe via the rear of the cabinets. Lesson learned here - never use it without the arbor drill bit! (recoil was crazy and kicked across the cabinet - just don't tell the missus!)...

Unintended re-route through the corner cabinet between the oven and sink. Does not obstruct the drawer use and is virtually concealed when the drawer is in place)...

My 'assistant' does his final checks - all good!

Hope this helps anyone doing a dishwasher install away from the drain - it is possible and will work!

Thanks again for everyone's help and advice - it was greatly appreciated.

 

[Edd99]

Just raised a similar thread on this topic but i wish i'd seen this first.....

Just out of interest, does your waste hose immediately exit the d/w and run along the floor or is there the high loop on the back before it runs along the floor? Thanks!

 

[just pumps]

Keep it high then create a fall on the pipe, no dips in the pipe for old water to hang around.

 

[Edd99]

Keep it high then create a fall on the pipe, no dips in the pipe for old water to hang around.

Thanks. I can't really keep it high because the other cupboards are in the way.

I'm really interested to know whether the guys (chappers and steve) had a high loop on the dishwasher as well as the sink or whether the pipe drain exited the dishwasher horizontally.

I appreciate this isn't best practice but i don't really have a choice :/

 

[just pumps]

I`d say it`s all in the pictures. High asap then run it through the cupboards high as you can then drop down to the kitchen sink waste.