OK PTP selection time...

[Alan Ambrose]

One of the many subjects I know nothing about. Scanning the forum, I get this in terms of number of hits:

 

Marsh - 51

Klargester - 84

WPL - 18

Tricel - 17

Graf - 79

Clearwater 9

Biorock - 22

WTE - 28

 

I expect that is roughly the market share - at least among self-builders.

 

I don't have biases except against the idea of the Klargetser 'biodisc' mechanics.

 

This is for a 3 bed. Ground is clay. Drainage to a culvert that three neighbours use already - I have EA approval for that already. I expect we'll install this ourselves.

 

All thoughts; biases; positive & negative experiences; tips, tricks etc gratefully received.

 

 

Edited June 14 by Alan Ambrose

[Nick Laslett]

I used these guys.

 

https://www.owlshall.co.uk/sewage-treatment/sewage-treatment-plants/1-4-bedroom/premier-tech-rewatec-asp-6-person-gravity-outlet/

 

Lots of technical support, found them very helpful. 
 

The Condor ASP 6 had a few people install back in 2018-19, like @ProDave. Most of my decisions are strongly informed by @Jeremy Harris, who was a strong advocate of many things and had a great blog, that is sadly no-more. 
 

This thread is possibly the one that pointed me in the direction of the condor asp 6. 
 

 

Edited June 14 by Nick Laslett

[Alan Ambrose]

Thanks - funnily enough, I had Owls over for a site visit way back for which they charged £100. They added very little to my knowledge bank re drainage, PTPs etc and said: 'we don't do consultancy or drainage design and can't recommend anyone else either. Or any contractors'. So much for their 'huge knowledge and experience' of drainage.

 

They we're hot on the blower though within a few days trying to heavy sell me a treatment plant. So, I felt I paid £100 for a sales visit.

 

Thanks for the ref to the BH threads.

Edited June 14 by Alan Ambrose

[Alan Ambrose]

Missed:

 

Harlequin - 6

 

p.s. here's the updated link to British Water's tables, we want the table for 'Part 3 PTPs':

 

List of Certified Small Wastewater Treatment Systems Up to 50PT

Edited June 14 by Alan Ambrose

[Alan Ambrose]

Anyone here used a 'Part 7: Prefabricated tertiary treatment units' after their standard PTP?

[JohnMo]

I am using a Harlequin 6. No issues.

 

Only real bugbear about most the units is the air compressor, it uses quite a bit of electricity over the year.

[Kelvin]

7PE Graf here. Easy enough to install. We don’t have a high water table so no worries about it popping out the ground when it’s due a pump out. The blower unit for the Graf is quite big and sits out of the ground so if it’s in your garden it could be visible. Fortunately it can be cited remotely from the PTP (up to 25m from memory) or obviously can be hidden. I fitted an external socket inside my blower unit to power the unit (rather than hard wiring it) That also  gives me power down that end of the field. 
 

The blower units  aren’t noisy but not silent either. Ours switches off and on rather than constantly running so uses less electricity. What is noisier is the process where the water exits the tank to the outflow. Makes a bubbling noise that’s accentuated by the SVP that exits just after the tank. Not an issue for us as it’s a long way from the house. More an issue for our sheep.

 

You might find that your local suppliers only stock certain brands. They are quite dear to transport from further afield. Therefore I’d phone around see what’s stocked locally before deciding. 

[crispy_wafer]

Another rewatec unit here, my self install post is about somewhere.  Didn’t go much into the science of choosing.  Remember something about the blower not running 100% of the time so marginal energy saving.  Those with a more enquiring mind could probably work out the long term costs of running.  Me?  Too worked up with the methods of how to install correctly 🤣

[Alan Ambrose]

Bio-Pure - 14

Conder - 111

[Alan Ambrose]

Is there any penalty to over-sizing a bit to get longer pump-out gaps? 

[crispy_wafer]

How many bathrooms/en suites will the unit be catering for?  6PE would be fine, but if you have the same number of bathrooms as bedrooms I’d probably go to an 8PE.

[Alan Ambrose]

Ah thanks.

[saveasteading]

6 hours ago, Alan Ambrose said:

number of hits:

Might include   'never use a xyz'.

 

BTW I met Marsh (52) at a recent presentation.

They have a new model that has...from memory....

only 2 chambers and supposedly better outfall numbers,  suitable for sensitive locations.

Costs £300? more, but costs less to run  as it turns off for 8 hours a day to let different bugs get to work.

So payback in a few years.

If the times were linked to cheap power then another saving.

I wonder if the pump also lasts 1/3 longer.

My next one is to a non-sensitive soakaway so I'm going to think further on this new Marsh (53).

[Alan Ambrose]

OK this is what I have so-far for anyone repeating this exercise:

 

PTP Comparison.xlsx

 

I'm leaning towards a conical one like Mr Harris and for the same reasons.

[saveasteading]

On 14/06/2025 at 18:47, Alan Ambrose said:

any penalty to over-sizing a bit to get longer pump-out gaps? 

I think so.   Starting with the logic that allowing rainwater into the sewage will reduce the effectiveness of the bugs. It is all designed to suit a certain murkiness.

The stuff passes through the chambers on the in = out principle. 

Too small a digester obv means it is passing through too quickly.

Too big and when it should be moving on, it is still in the earlier chamber, diluting the solution, and not optimising the right kind of bugs.

 

BUT, the tanks are always designed up to the next size, and most are oversized fig actual use,  so it can't be a serious problem.

 

Another BUT.    In my experience they don't need pumping out very often at all, not for organic sludge anyway...perhaps for stuff that should not  have been flushed.