Underground cable advice please

[Lincolnshire Ian]

Hi everyone 

We are just starting groundworks and this will include laying drains to the private drainage plant. In the same trench, above the waste water, I want to bury an armoured electrical cable to power the aerator and the pump. 

As we are at the start of our project we haven't engaged a sparky yet. Can anyone suggest what type of cable I should get?

I have taken some pictures of the set up. 

Thanks 

[cjsparkey]

Could you install a duct with draw rope then pull the cable in at a later date once you have your sparky sorted.

[ProDave]

the aerator is tiny power 75W.

 

What is the "pump"?  What is that doing?  Pumped discharge to soakaway at a higher level or what?  That is likely to me a much higher power rating.

 

How far from consumer unit to treatment plant?

 

What do instructions say?  Can both pumps share a single supply or do instructions say they must have separate supplies?

[FarmerN]

Would you want to extend the power supply from it in the future for a greenhouse, garden room or workshop?

About to extend electrical feed from my treatment plant to a workshop.

[Kelvin]

Put duct in and park the cable decision until you come to do it. We ended up putting a slightly bigger cable in than necessary to allow us to extend the supply to the bottom of our field from the blower unit housing. In fact put all your cables in ducts. It’s relatively cheap and makes life easier down the line when  things inevitably change. Also put more ducts into the house/garage than you actually need. I did n+2 in the house and ended up using both of them. You could argue better planning would have avoided the need but it’s better to have them and not use them than need them and not have them. I also put an extra duct into our electricity kiosk which was fortunate as our EV charger was installed differently from how we originally planned it. 

Edited Thursday at 09:06 by Kelvin

[saveasteading]

I've seen cables sticking in ducts, resisting the winch tension.... scary.

Had to dig another draw point.

You must not have any wobbles in the duct. None, zero.

[Kelvin]

12 minutes ago, saveasteading said:

I've seen cables sticking in ducts, resisting the winch tension.... scary.

Had to dig another draw point.

You must not have any wobbles in the duct. None, zero.

We had the duct split at the joiner for the huge main supply cable. That was a long day. Fortunately it split 2m from the kiosk so it was easy to find as you could hear the cable bang against the other end of the duct. Had to dig down to it by hand to repair then get the cable in. Our ducting route for the cable wasn’t ideal either as it went through two turns plus the down and up from the house to the kiosk. Was a nervy few days for my wife and I trying to get the cable through. In hindsight I ought to have moved the kiosk location to give the ducting a straighter run. I’d still advocate ducting though just be careful with bends and be sure the joins are sound. 

Edited Thursday at 10:08 by Kelvin

[saveasteading]

If you have the luxuries of space and time, then working with an open trench, or part,  removes these risks entirely. 

[Temp]

To spec the cable you need the total  power or current draw and the length of the cable not just the trench.

 

I would put SWA cable and a draw rope in a duct. Put the rope and cable in the duct before burying it.